JP2009194924A - Apparatus and method for generating sound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and method for reproducing recorded sound or sound delivered by broadcasting and for generating sound from an electronic acoustic instrument (in particular, a digital-type piano). <P>SOLUTION: The method and apparatus for reproducing sound utilizes both distributed mode speakers and piston-type speakers simultaneously driven over at least partially overlapped frequency ranges to emphasize spaciousness of the generated sound. The disclosure includes sound reproducing systems of monophonic, stereophonic, and multichannel types, and electronic acoustic instruments such as a digital-type piano. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an apparatus and method for generating sound, including a novel speaker assembly and a novel electronic circuit for driving the speaker assembly. The present invention is particularly applicable to the reproduction of recorded sounds or broadcasted sounds, as well as the generation of sounds from electronic audio equipment (particularly digital pianos).

  Over the last few decades, the generation and reproduction of sound has always been the subject of research and development. One aspect of such research is aimed at improving the fidelity and quality of the sound produced by the speaker in relation to the operating performance of the speaker, for example, so that the movable element of the speaker faithfully follows the variation of the electrical signal that drives it. The purpose is to produce a loud speaker. Another aspect of research and development is related to techniques for encoding, recording, broadcasting, and decoding electrical signals that represent sound, and the realism of the sound when played on a speaker driven by the decoded signal ( The aim is to improve the realism.

Fidelity and speaker design From the results of research on speaker improvements, many numbers of different types of speakers, each operating on different principles, are currently available.

  For example, there is a conventional cone speaker in which a cone mounted on a relatively rigid material is electromagnetically driven by a moving coil or a moving magnet. This type of speaker is probably the most widely supported, and is used in a wide variety of different applications, each with its own specific design requirements. Examples of such applications are home entertainment systems for reproducing music, speech or audiovisual material, public sound systems, computer audio output, cinema and theater sound systems, in-car entertainment, public sound systems. , As well as in electrical or electronic acoustic equipment such as digital pianos.

  No cone-free speaker has yet been devised that can produce good fidelity sound over the entire range of audible frequencies (specifically, from below 50 Hz to about 20 kHz). Thus, good quality sound (eg, for high fidelity music playback) uses a cone speaker in combination with two or more units, each designed for a particular frequency band. Only when this can be achieved. The drive signals for these units are accordingly passed through a circuit called a crossover circuit that leads different frequency bands of the drive signal to the appropriate cone speaker. Many high quality speaker systems typically utilize at least three cone speakers, one of which is called a high frequency tweeter and the other is a mid range speaker. The third is a speaker called a low-frequency woofer or subwoofer. Modern cone-speaker systems can play sound with a relatively flat frequency response with relatively high fidelity over virtually the entire frequency range that is audible to humans, and so far the best for music playback. It is a type of speaker that is widely used.

  Another type of loudspeaker used is to vibrate a lightweight stretched plastic membrane by alternating the electrostatic field generated from the drive signal by a pair of electrodes with the membrane positioned between them. It is an electrostatic speaker. This film is particularly lightweight and therefore has a low mechanical inertia, so that signals applied by the movement of this film can be reproduced with relatively high fidelity even at high frequencies. One specific feature of the electrostatic speaker is that the clarity of the generated sound is higher than that of another type of speaker. However, currently available electrostatic loudspeakers cannot generate the lowest frequencies that can be produced in music. While this and the sound pressure level generated by electrostatic speakers may be lower than the sound pressure level that can be generated by cone speakers, many people find that electrostatic speakers are particularly useful over the operable frequency range. We believe we can provide high fidelity.

  The cone and electrostatic speakers described above generate sound by the piston-type motion of the cone or membrane.

In recent years, a third type of speaker that does not rely on piston-type motion has been put into use. This speaker is called a distributed mode speaker. This is described in many publications as shown below, for example.
(A) PCT application WO 97/09842 (b) U.S. Pat. No. 6,399,870 (c) Hachette Filpacchi Magazines Inc. Article titled “NXT Up Against the Wall” by Henry Azima published in the September 1998 issue of the magazine “Audio” published by (d) The 103rd Audio Engineering Society Convention (September 26-29, 1997) A paper titled “The Distributed Mode Loudspeaker (DML) as a Broadcast-Band Acoustic Radiator in the 19th Annual of the 19th Annual of the 9th Annual (e) in the 9th Annual of Evidence” Henry Azi announced at New York on the 29th According to the a and Neil Harris "Boundary Interaction of Diffuse Field Distributed Mode Radiators entitled" paper (f) the 104th Audio Engineering Society Convention (5 May 16-19, 1998, Amsterdam) Joerg W. published in the Paper titled “Distributed Mode Loudpeaker Simulation Model” by Panzer and Neil Harris (g) The 105th Audio Engineering Society Conference (January 26-29, 1998, San France) A paper entitled "Distributed Mode Loudpeaker Radiation Simulation"

  The contents of these publications are incorporated herein by reference. The structure and operation of such distributed mode loudspeakers are also described in many other published papers, some of which are referenced in the articles and papers listed above.

  As described in the publication above, a distributed mode speaker has one panel and the panel attached to the panel and subjected to activation by an electroacoustic signal relative to the panel. One or more transducers generating resonant bending waves that are distributed in a complex pattern over the entire surface (or a required portion of the surface). In order for a transducer to excite a panel into these distributed resonant modes, the panel must be constructed to be excited to be in these resonant modes, and the one or more transducers in the panel. It needs to be carefully positioned taking into account the properties of the panel so that the required resonant mode is generated. Those skilled in the art of distributed mode loudspeakers can design such loudspeakers in a variety of sizes and using a variety of different materials and different forms of transducers.

  The method of vibrating the panel and its frequency response are as follows: panel width, height, thickness, material, material density, Poisson's ratio, bending stiffness, damping factor, shear ratio, shear modulus, transducer properties and placement Proper design of a distributed mode speaker is a complex operation because it depends on a number of different parameters including the number of transducers to perform. In practice, this frequency response needs to be calculated from a mathematical formula (for this, see the publications given above relating to distributed mode speakers). A computer program for performing these calculations and thereby facilitating the proper design of distributed mode speakers is New Transducers Limited (Signet House, Kingfisher Way, Hinchingbrook Business Park, Huntingdon; ZIP Code PE29 6F). Available on the market. This computer program allows the designer to enter or select various related parameters for the proposed speaker, which calculates the frequency response and vibration characteristics obtained for the proposed speaker. It allows designers to make appropriate design decisions.

  In addition to the computer programs described above, distributed mode speakers may be, for example, Amina Technologies Ltd (Cirrus House, Glebe Road, Huntingdon, Cambridgeshire PE29 7DX, England); Ltd. (Stonehill, Huntingdon, Cambridgeshire PE29 6EY, England); or Armstrong World Industries (available from different sources such as 2500 Columbia Avenue, Lancaster, PA 17603, USA)

  Various proposals have been made for deployments combining different forms of distributed mode speakers. For example, currently available distributed mode speakers cannot faithfully reproduce frequencies below about 100 Hz, so they are used with a subwoofer separate from the distributed mode speakers and these two speakers are used appropriately. Driving through a filter processing (crossover) circuit has been proposed. In addition, a distributed mode speaker used as a tweeter, one or more conventional cone and / or mid-range speakers acting as a woofer, and a conventional crossover circuit are combined in a common casing. The distributed mode speaker is driven exclusively by frequencies in the band suitable for the tweeter, and the one or more cone speakers are exclusively driven by frequencies in the band suitable for woofer and mid-range speakers. There are commercially available loudspeaker assemblies that are actuated.

  Another proposal for a full frequency range speaker system utilizing distributed mode speakers is described in US Pat. No. 6,351,542 (Azima et al.). In this patent, a distributed mode speaker forms one wall of a closed chamber connected via a pipe to a housing containing a low frequency speaker (woofer), thereby enclosing the housing containing the woofer. The fluctuation of the air pressure generated in the body is transmitted to the closed chamber through the pipe. The distributed mode loudspeaker can move in a piston-like manner in response to air pressure fluctuations in a closed chamber by being supported by a compliant material at its marginal position, so that a piston-like vibration synchronized with the woofer. Can efficiently generate low-frequency sound.

  The published PCT application WO 97/09842, already referred to above, by itself discloses a number of potential applications and arrangements for distributed mode speakers. One of the arrangements disclosed in this PCT application proposes the use of a curved panel within a distributed mode speaker to converge the sound in a particular direction. Another arrangement (FIG. 65 of the PCT application) is that a conventional speaker casing includes at least one wall that is capable of resonant mode vibration but not via an electromagnetic transducer, including a woofer, midrange and tweeter. It is proposed to form a passive panel that is vibrated by resonance induced by fluctuations in air pressure generated inside the speaker housing when the type cone speaker is driven. This arrangement is said to allow the desired properties to be achieved.

  One of the important advantages of distributed mode speakers is that they can be made with relatively flat side shapes, which makes them inconvenient or visually disturbing for cone speakers. It is possible to use it in the situation. However, distributed mode speakers have not yet achieved widespread use in the field of high fidelity music playback, perhaps because they can produce sound over most of the frequency range that humans can hear. This is because the frequency response is still not as flat as can be achieved with a properly designed cone speaker.

Realism and sound encoding techniques Research that improves the realism of the sound being played back positions the recording to the left and right of the listener in front of the listener when recording or broadcast distribution is provided on separate channels. Developments have been made in stereo acoustic systems that include different signals for driving loudspeakers. These systems became widely available on the market in the 1950s and 1960s and continue to be used. According to this, it is possible to generate an impression that the sound is generated at a different location in front of the listener and the sound is moving across the sound “stage”. This can also provide a spatialness and full sound impression, such as those produced by acoustic equipment such as symphony orchestra, and play sound using a single signal channel. It is better than what you get by doing.

  To further improve the impression of space, and to provide the possibility of special effects such as apparently moving the sound source through the 3D space where the listener is located, there are 4 channels in the 1960s A system (referred to as a quadraphonic system) has been developed. At this point, some of the records and some of the broadcast distributions were produced, but the quadraphonic system was not widely used at that time. One of the problems with this system is that it requires special recording and broadcast distribution techniques where different signals are encoded on different channels, and the four speakers are positioned essentially in the four corners of the listening room. The need to position the hand in the central region of the space between the four speakers. Although these systems were not widely used at the time, the impression of spaciousness (ie, the listener listening to the sound in a substantially larger room compared to the room in which the listener actually listens) As well as “envelopment” (ie, creating a sense of feeling that the listener is surrounded by sound), some kind of improvement over stereophonic systems Could have obtained. These impressions come together when listening to music in a concert hall where the acoustic properties are to provide the appropriate reflection level and appropriate reverberation time for the sound from the walls. Provides a psychoacoustic experience that is very similar to the experience expected to be obtained.

  In recent years, so-called “surround sound” systems have come into use, particularly in cinemas and so-called “home cinema” entertainment systems. One of the main purposes of a surround sound system is to generate special sound effects such as simulation of sound by a vehicle passing through a space that encompasses the surround sound system and the listener. Typically, a surround sound system has five channels to drive the left and right speakers in front of the listener, the left and right speakers on the side of the listener, and the front center speaker, respectively. In this system, when encoding for signal recording or broadcast distribution, the signals to be reproduced are individually encoded in each of five different channels so that each separate speaker can be individually driven by its dedicated signal. It is necessary to have received. With proper signal encoding, a surround system can provide improved spatial and envelope characteristics of the sound compared to a stereo acoustic system.

PCT application WO 97/09842 US Pat. No. 6,399,870

Henry Azima, “NXT Up Against the Wall” (“Audio” September 1998 issue) Neil Harris and Malcolm Omar Hawksford, “The Distributed Mode Loudspeaker (DML) as a Broad-Band Acoustic Radiator 97 (November 103, Audio Engineering 19 Henry Azima and Neil Harris, “Boundary Interaction of Diffuse Fielded Mode Radiators” (103rd Audio Engineering Society, 26th, 1997, 29th, 1997) Joerg W. Panzer and Neil Harris, “Distributed Mode Loudpeaker Simulation Model” (104th Audio Engineering Society Convention (May 16-19, 1998, Amsterdam)) Joerg Panzer and Neil Harris, “Distributed Mode Loudpeaker Radiation Simulation” (105th Audio Engineering Society Convention, September 26-29, 1998, San Francisco)

The system, particularly the sound space, that can generate enhanced sound from an electrical signal at a reasonable cost, despite the extensive improvements in speaker design and signal encoding achieved over the past decades as discussed There is a need for a system with improved breadth.

  In one aspect, the invention provides for simultaneously driving at least one piston-type speaker and at least one distributed mode speaker such that the frequency range in which the speaker operates overlaps at least a portion of the frequency range that is audible to humans. Improvements in space expansibility and / or envelope are achieved. This overlapping portion of the frequency range preferably includes at least a relatively low frequency.

  Surprisingly, it has been found that by playing sound in this manner, spatial and / or envelope enhancement can be achieved even in a single channel (mono) system. Thus, the present invention is applicable to single channel, stereophonic and multi-channel sound reproduction systems.

  By carrying out the emphasis on space expansibility, or even on the envelope and the warmth of its sound, and referring to the comparative experiments shown in FIGS. 1-7 of the accompanying drawings. We will consider further below. Practical embodiments of the present invention will be described with reference to FIGS. 8 to 31 of the accompanying drawings.

Stereo acoustic sound reproduction comparing lateral initial energy ratios (LEFs) obtained using a conventional cone speaker alone, a distributed mode speaker alone, or a combination of both, according to an embodiment of the present invention. It is a bar graph showing LEF measured in the 1st experiment using a system. FIG. 2 is a bar graph representing the interaural cross-correlation coefficient (IACC) measured in the experiment mentioned in connection with FIG. It is the same bar graph as FIG. 1 showing LEF obtained by the 2nd experiment using a mono sound reproduction system. FIG. 3 is a bar graph similar to FIG. 2 showing IACC obtained in a second experiment using a mono sound reproduction system. It is a figure showing the frequency response of the conventional cone speaker used in the 3rd experiment relevant to this invention. It is a figure showing the frequency response of the dispersion mode speaker used in the 3rd experiment relevant to this invention. FIG. 7 is a diagram of the frequency response obtained when simultaneously driving the speakers corresponding to FIGS. 5 and 6, in which the results obtained when the relative sound pressure levels of the two speakers are changed are represented by different curves, respectively. . 1 is a block diagram of a stereophonic sound reproduction apparatus according to a first embodiment of the present invention. FIG. 9 is a schematic perspective view of a speaker assembly included in the apparatus of FIG. FIG. 10 is a schematic cross-sectional view of a portion of a distributed mode speaker included in the assembly of FIG. 9 showing an electromagnetic actuator attached to the speaker panel. FIG. 10 is a schematic perspective view of a portion of the distributed mode speaker of the assembly of FIG. 9 illustrating the mounting of the speaker panel in a support frame. FIG. 10 is a schematic side cross-sectional view of the speaker assembly of FIG. 9 representing a schematic block circuit diagram of the assembly. It is a block diagram of the stereophonic sound reproduction apparatus by the 2nd Embodiment of this invention. FIG. 14 is an electrical block diagram of a signal conditioning circuit for driving a distributed mode speaker included in the apparatus of FIG. 13. FIG. 15 is an electrical block diagram constituting a partial electrical block diagram according to a third embodiment of the present invention, showing a modification of the circuit of FIG. It is a block diagram of the stereophonic sound reproduction apparatus by the 4th Embodiment of this invention. It is a block diagram of the stereophonic sound reproduction apparatus by the 5th Embodiment of this invention. It is a block diagram of the stereophonic sound reproduction apparatus by the 6th Embodiment of this invention. FIG. 19 is an electrical block diagram of a stereo acoustic amplifier included in the apparatus of FIG. 18. It is a block diagram of the stereophonic sound reproduction system by the 7th Embodiment of this invention. It is a block diagram of the stereophonic sound reproduction system by the 8th Embodiment of this invention. It is a schematic perspective view of the stereophonic sound reproducing apparatus according to the ninth embodiment of the present invention. FIG. 23 is a schematic circuit diagram of a part of the apparatus shown in FIG. 22. It is a block diagram of the stereophonic sound reproduction system by the 10th Embodiment of this invention. FIG. 20 is a block diagram of a “surround sound” sound reproduction system according to an eleventh embodiment of the present invention. 1 is a perspective view of a digital grand piano according to an embodiment of the present invention. It is a block schematic diagram of the digital piano of FIG. 1 is a rear perspective view of a digital upright piano according to an embodiment of the present invention. It is a block diagram of the digital piano of FIG. It is a block diagram of another embodiment of the digital piano by this invention. FIG. 6 is a block diagram of an add-on unit according to another embodiment of the present invention, shown connected to a conventional digital piano so as to implement the present invention in combination with a conventional digital piano.

General Introduction to Experimental Experiments In order to investigate the tremendous increase in the impression of spatial spaciousness achieved by combining distributed mode and piston type speakers according to the present invention, in many different environments and in this different environment Many experiments were conducted using different speakers and different devices.

  For all of these experiments, it was essential to use a top quality studio monitor cone speaker system and a top quality distributed mode speaker. Each experiment includes a subjective listening test performed on an expert listener, but different experiments have different target listeners.

  One experiment (the first experiment to be described in detail below) is placed in a specialized listening room designed to mimic acoustically typical listening conditions, such as in a living room at home. A stereo acoustic system is used. This listening room is roughly the same size as a large living room with reflective and non-reflective surfaces around randomly distributed walls, floor carpets and some highly absorbent furniture. It is. This acoustic characteristic is relatively “dead” as in the living room including soft furniture and curtains.

  The second experiment uses a mono device that is half the size of the room used in the first mentioned experiment above and is in a different specialized listening room that absorbs frequencies above 10,000 Hz. Carried out. Similar to the first listening room, the acoustic characteristics were relatively “dead”. A mono device was used.

  The mono apparatus was also used in the third experiment described further. The loudspeakers were positioned with particularly unfavorable acoustic properties at the point of intersection of two corridors, each about 2 meters wide and extending perpendicular to each other. The listening test was conducted with the subject in one of the corridors approximately 3 meters from the speaker, with the speaker facing the corridor where the listener was positioned.

  For all experiments, the subjective listening test shows that the spatial expanse when driving a distributed mode speaker and a cone speaker simultaneously is the same as when driving the cone speaker alone, or driving the distributed mode speaker alone. A perceptible improvement was seen compared to the case of letting go. In order to determine whether the perceptible increase in spatial breadth is merely subjective, i.e. whether it has a scientific basis, the first and second experiments used conventional measurements. Lateral Early Energy Fraction (LEF) and interaural cross correlation coefficient (IACC) were measured according to the technique. The nature of LEF and IACC will be described more fully below.

  The subjective quality of the sound produced by the different devices used in these experiments is also considered in the listening test. In the first experiment (stereo acoustic type), the sound pressure levels of the distributed mode speaker and the cone speaker are set to substantially the same value at the position of the measurement microphone, and the cone speaker is used alone or It was subjectively considered that the quality of sound from a composite speaker was better than the quality of sound produced by a distributed mode speaker alone.

  In the second experiment, the sound pressure level of the distributed mode speaker was set to be 4.2 decibels lower than the sound pressure level generated by the cone speaker (measured at the microphone position). This number was determined after trying many different relative sound pressure levels. The quality of the sound generated by the composite speaker was also considered better than the sound generated by the cone speaker alone or the distributed mode speaker alone.

  In the third experiment, the effect of changing the relative sound pressure level of the distributed mode speaker and the cone speaker on the subjective quality of the sound was tested, and the distributed mode was reduced by 5 dB ± 3 dB below the cone speaker. It has been found that driving the speaker gives the best perceptual quality, and this quality is better than the perceived quality when listening to a distributed mode speaker or cone speaker alone I understand.

The third experiment further included measurements to determine the frequency response of the two speakers alone and the frequency response of the composite speaker. The frequency response of the composite speaker was determined for a number of different relative levels at which the speaker was driven. From these experiments and calculations, it was found that the composite type speaker can obtain a frequency response curve that is smoother than the frequency response of the distributed mode speaker alone.
We will now describe each of these three experiments in more detail.

Details of the first experiment (stereo) The first experiment was conducted using the following apparatus under the following conditions.

  (A) The listening room was a typical drying room with additional absorbent panels randomly placed on the side and back walls. The size of this room was length 6.87 m × width 4.6 m × height 2.79 m = volume 88.17 cubic meters.

  (B) The speaker and the microphone were arranged at the positions of the vertices of the equilateral triangle. The distance between the speaker and the microphone was 2 meters (each side of the triangle = 2 meters). The speakers were positioned so as to be spaced from the walls of the listening room.

  (C) This speaker consisted of two conventional cone speakers and two distributed mode speakers.

  (D) The conventional cone speaker was a Genelec model 1029A 40W monitor with an integrated amplifier. Technical data: bus 5 "drive unit; treble 3/4" metal dome drive unit; crossover frequency 3.3 kHz; frequency response 70-18,000 Hz.

  (E) The distributed mode speaker was manufactured by Amina Technologies Limited (referenced above) and was equipped with a 610 mm x 492 mm aluminum core, polyester skin, 4 exciter (10 W / exciter) . Each of these was a 40 W open back panel. The frequency response was 80 Hz to 20 kHz.

  (F) For LEF measurement, a CALREC Soundfield microphone, model ST250, was used. The IACC measurement used was a B + K Head and Torso Simulator (HATS) microphone, model 4100.

  (G) In these measurements, a maximum length sequence signal was used, the impulse response was extracted, and a spatial measurement was performed on the impulse response. The software used was P.I. of Cool Edit Pro with Aurora Plugin. C. It was a version.

  (H) The distributed mode and cone speakers were driven to provide substantially equal sound pressure levels at the microphone location.

A listener located in a listening space such as a concert hall receives both sound energy directly from the source (eg, orchestra) and sound energy after being reflected at the boundary of the listening space. The fraction of total energy received by a listener who receives reflections from the boundary of the listening space within a period of approximately 50 milliseconds after receiving a direct sound is known as the lateral initial energy ratio (LEF). Yes. Higher frequencies absorb more compared to lower frequencies, and generally contain less energy than lower frequencies, so the majority of reflected energy is in the lower frequency range. Is in. LEF measures in a conventional manner in many frequency bands (especially the following bands).
88-176 Hz (referred to as 125 octave band)
176 to 353 Hz (referred to as 250 octave band)
353 to 707 Hz (referred to as 500 octave band)
707 to 1,414 Hz (referred to as 1,000 octave band)

  Within the limits, it is widely considered that the higher the LEF of these frequency bands, the greater the impression of space expanse in the concert hall environment. Since the object of the present invention is to generate an improved impression of spatial spaciousness, LEF measurement is performed on a composite sound field generated by simultaneously driving a distributed mode speaker and a cone speaker. This is compared with LEF measurement when the distributed mode speaker and the cone speaker are driven individually.

  FIG. 1 is a bar graph showing the results. As can be seen from this figure, the vertically striped bars 500a, 500b, 500c and 500d each represent the LEF for a cone speaker alone in each of the octave bands defined above. Horizontal stripes 502a-502d represent LEFs for a distributed mode speaker alone in the same octave band. Interstriped bars 504a-504d represent LEFs for a combined distributed mode speaker and cone speaker according to the present invention.

  As can be seen from FIG. 1, in each of the octave bands, the LEF for the sound field generated by the composite distributed mode / cone speaker according to the present invention is compared to the LEF for the sound field generated by the cone speaker alone. Remarkably high. Thus, FIG. 1 shows that the subjectively perceived significant increase in the impression of spatiality achieved by a composite speaker according to the present invention compared to a cone speaker is an increase in LEF within these octave bands. Consistent with, and according to this, is consistent with the widely held view that the increase in LEF in these frequency bands provides an increased impression of space in concert hall environments. Show. In other words, the sound field generated by the composite loudspeaker according to the present invention in the first experiment increases the value of the important parameter (LEF), which is considered to be related to the improved impression of spatial spaciousness. Is different from the sound field generated by a cone speaker alone. This is because the increase in spatial breadth perceived in the subjective listening test mentioned above is that the production of the sound range when using the composite type according to the present invention is physically different from the sound field produced by the cone speaker alone. It is considered to be confirmation that it is due to generation.

  Furthermore, in the 125 and 250 octave frequency bands, the magnitude of the difference in LEF between the composite speaker and the cone speaker is substantially larger than the difference in LEF in the 500 and 1,000 octave frequency bands, and thus this characteristic. It is also observed that is associated with an increase in the warmth of the sound. In other words, if the magnitude of the difference in LEF in each of the four octave frequency bands shown in FIG. 1 is the same, this increases the spatial breadth but not the warmth of the sound. I would suggest that.

  Note further from FIG. 1 that the distributed mode speaker alone LEF is greater than the cone speaker alone LEF for all four frequency bands. In the 125 and 250 octave frequency bands, the LEF of the distributed mode speaker alone is smaller than the LEF of the composite speaker. In the 500 and 1,000 octave bands, the LEFs of the distributed mode loudspeaker alone and the composite loudspeaker are similar in size, and the differences seen in these octave bands are almost certainly not perceptible by themselves. . As these results are supported by subjective listening tests, the spatial breadth using the composite speaker according to the present invention for the distributed mode speaker is not as great as that of the cone speaker alone. This suggests that it provides greater space expansibility compared to cone speakers. However, the importance of the present invention is that a significant increase in spatial breadth compared to that obtained with a cone speaker alone is provided while maintaining fidelity. Note that distributed mode speakers are not yet widely used in applications where the highest level of fidelity is required.

The interaural cross-correlation coefficient (IACC) is a measure of the degree of correlation between sound pressure signals received by the listener's ears. IACC is therefore measured traditionally using a dummy head having openings at the location of the human ear canal and a small microphone within each opening. It has been widely considered that the low value of this correlation coefficient in one or more of the 1,000, 2,000 and 4,000 octave frequency bands suggests an increase in spatial breadth, The values in these bands are as follows:
1,000 bands: 707 to 1,414 Hz (same as already shown above)
2,000 bands: 1,414 to 2,825 Hz
4,000 bands: 2,825 to 5,650 Hz

  FIG. 2 is a bar graph showing the results of IACC measurement performed in the first experiment. In FIG. 2, four octave bands (ie, 500 octave bands (described above in connection with LEF, respectively) are shown by vertical stripe bars 506a-506d, horizontal stripe bars 508a-508d, and cross stripe bars 510a-510d, respectively. ) And 1,000, 2,000 and 4,000 octave bands) respectively, IACC for a cone speaker alone, IACC for a distributed mode speaker alone, and IACC for a combination of both according to the present invention. . As can be easily understood from this figure, in the 1,000, 2,000 and 4,000 octave bands, the IACC value for the composite speaker according to the present invention is significantly smaller than the IACC value for the cone speaker alone. . Here as well as in the case of LEF values, this suggests an increase in the spatial breadth of the sound, as explained above, because the smaller the value of this coefficient in these frequency bands, the smaller the spatial breadth. This is because the impression of becomes larger.

  Figure 2 includes IACC measurements in the 500 octave band, but the sound energy wavelength in this frequency band is expected to have a high correlation coefficient in the energy received by the listener's ears, as is well known. Therefore, these measurements are not really important.

  Thus, it can be seen that the LEF and IACC measurements for the stereophonic device used in the first experiment are both consistent with the subjective impression of spatiality observed in the listening test.

Details of Second Experiment (Mono) The second experiment was conducted using the following apparatus under the following conditions.

  (A) The listening room was acoustically treated to absorb sound above 10,000 Hz (average reverberation time 0.3 seconds). The size of this room was length 5.6 m × width 3.2 m × height 2.4 m = volume 43.28 cubic meters.

  (B) The microphones for these measurements were placed 1.5 meters from the speaker with the same axis. The front surface of the distributed mode speaker was aligned generally vertically with the rear surface of the casing of the conventional cone speaker.

  (C) The cone speaker was Tannoy's Near Field Dual-Concentric Monitor Model 6NFM Mark II with a frequency response of 44 Hz to 20 kHz. The advantage of this unit is that HF and LF are at the same axial point in the measurement. The distributed mode speaker panel used was manufactured by Mina Technologies Limited and provided with a skin having a 500 × 700 mm resin-impregnated paper honeycomb core and four exciters (10 W / exciter). This is a 40 W open back panel with a frequency response of 80 Hz to 20 kHz.

  (D) For LEF measurement, AKG C34 Variable Polar Microphone was used. For the IACC measurement, Neuman Binaural Head was used.

  (E) Again, the impulse response and spatial data were extracted from the maximum length signal. The software used was MLSSA P.M. C. Software.

  (F) A separate amplifier was used and the DML panel was set lower by 4.2 dB compared to Tannoy.

  3 and 4 are bar graphs representing LEF and IACC measured in the second experiment. The striped pattern for each bar has the same meaning as in FIGS. Therefore, the bars 512a-512d in FIG. 3 and the bars 518a-518d in FIG. 4 show LEF and IACC of the cone speaker alone, respectively, and the bars 514a-514d in FIG. 3 and the bars 520a-520d in FIG. 3 shows the LEF and IACC of a distributed mode speaker alone, and the bars 516a-516d and 522a-522d of FIGS. 3 and 4 respectively show the LEF and IACC of a combined digital mode / cone speaker according to the present invention. Yes. As in FIGS. 1 and 2, each bar in FIGS. 3 and 4 shows the associated value for a particular octave frequency band as shown in the figure.

  The test of FIG. 3 shows that the LEF value of the composite speaker according to the present invention is higher than the LEF of the conventional cone speaker alone or the LEF of the distributed mode speaker alone in each octave frequency band. This is consistent with the increase in perceivable spatiality observed in subjective tests, as explained above. The magnitude of the difference between bars 516b and 512b is greater than the magnitude of the difference between bars 516c and 512c (250 and 500 octave band LEF values), indicating a significant improvement in the warmth of the sound.

  FIG. 4 shows that in the 1,000 and 4,000 octave bands, the IACC of the composite loudspeaker according to the present invention is much lower than the IACC with a cone loudspeaker alone. This is consistent with the observed increase in spatial breadth. However, in the 2,000 octave band, the IACC values 518c and 522c are almost the same. As described with reference to FIG. 2, the IACC values shown in FIG. 4 are not significant for the 500 octave band.

  FIGS. 3 and 4 are both consistent with a surprising and significant increase in the impression of spatiality perceived in subjective tests with the mono system used in the second experiment.

Details of Third Experiment (Mono) This experiment was conducted using a different apparatus in an environment different from the environment and apparatus of the first and second experiments described above. This experiment consists of a subjective test using a single channel (mono) with inconvenient acoustic characteristics (same as already described above) and frequency response measurements performed in an anechoic chamber. LEF and IACC measurements were not performed in this experiment.

  The conventional cone speaker used throughout these measurements was a JBL LSR32 passive studio monitor with three drive units covering a frequency range of approximately 30 Hz to 20 kHz. DML is available from Amina Technologies Ltd. Was manufactured. The DML panel consisted of a resin-impregnated paper honeycomb core with a resin-impregnated glass fiber skin and a size of 60 cm × 60 cm. There were four electromagnetic exciters and the frequency response was 80 Hz to 20 kHz.

  The DML panel was placed on top of a conventional speaker and attached using a strong double-sided adhesive tape. Pink noise as a test signal for all measurements (pink noise is a wideband random signal containing equal signal energy per octave bandwidth to ensure proper signal-to-noise ratio at all frequencies of interest. Used). The output signal from the signal generator was connected to the input of a two-channel power amplifier through a pair of universal filter sets to allow adjustment to the frequency range of the signal supplied to each speaker. The relative power levels of the two speakers were adjusted by using an attenuator that was switchable in-line to the amplifier that powers the conventional speaker.

FIG. 5 shows the magnitude of the on-axis frequency response of a conventional cone speaker, and FIG. 6 shows the magnitude of the on-axis frequency response for the DML panel. Represents. The low frequency response of the DML panel was cut below 100 Hz according to the manufacturer's recommendations. The in-line attenuator was adjusted so that approximately the same coincidence level was obtained from two speakers in the frequency range from 500 Hz to 5 kHz.

  The frequency responses shown in FIGS. 5 and 6 were summed on the computer both with and without phase consideration. The comparison between the obtained frequency responses, as well as the measurement of the frequency response obtained when the speakers were clearly combined, showed that an additional phase and thus interference occurred between the two speakers. In short, surprisingly, the frequency response of the combined output from the two speakers can be accurately determined by adding the individually measured responses in consideration of the phase. If this is true, the combined response can be determined at any relative output level. FIG. 7 shows the frequency response of such a synthesis determined on the computer as described immediately above, with the DML level varying from −12 dB to +12 dB in 3 dB steps relative to a conventional speaker. Yes.

Subjective evaluation The subjective test was performed on the same equipment used in the measurement, but on two speakers in a semi-reverberant space (shutoff corridor as described above) rather than in an anechoic chamber.

  All listening was performed on a single channel mono using a variety of commercially available music records reproduced from compact discs. First, a significant change in spatial breadth was perceived when the DML panel was switched in and out. All subjects acknowledged that the addition of panels improved the sense of spaciousness compared to the conventional cone speaker alone. Second, the relative levels of the two speakers were changed until they reached a consensus at an optimal level to obtain an improvement that all subjects could perceive. This was done using a “balance” control on the amplifier while keeping the overall level constant. All subjects agreed with the optimal level setting of -5 dB output from the DML panel based on the level used in the above measurement (equal level from 500 Hz to 5 kHz). All subjects agreed within this range of ± 3 dB.

  An additional test may establish a relative level threshold so that the detectable sound change does not exceed that value when one speaker is switched in and out and the other is held constant. It was essential. This level was quickly determined to be about -35 dB detection threshold for DML panels and -20 dB for conventional speakers.

DISCUSSION This frequency response measurement clearly shows that the DML panel has a frequency response that is less smooth than a conventional cone speaker. This is not so surprising when considering various radiation mechanisms. The DML panel also shows a noticeable decrease in response around 7 kHz. However, what is surprising is how much the DML panel and the conventional speaker interfere. Because the vibration field across the surface of the panel is essentially diffusive, the DML panel emits sound in the direction in which it operates. Thus, while it is quite reasonable to predict that there is no particular phase associated with the radiated sound field, the result of these measurements is at least a single point in space and a narrow frequency band ( However, for all audible frequencies, this panel has a measurable and repeatable phase response that causes a constructive interference with the sound emission from another speaker. Show.

  FIG. 7 shows the frequency response for the combined output of the two speakers when the level of the DML panel is varied with respect to the level of the conventional cone speaker. As can be expected, a low level of DML output has little effect on the response of a conventional cone speaker, and a high relative level indicates a response overwhelmed by the response of the panel. However, the most interesting point to note about this figure is the relative level at which the response of a conventional cone speaker, which is normally smooth, is disturbed at that level by interference from the output of the DML. . This figure shows that in this experiment, at relative levels above -3 dB, the response is adversely affected by the panel, but not at lower levels. According to this subjective observation, a relative level of -5 dB is near the optimum for favorable sound quality, and when the relative level of the DML output is high, the improvement of spatial expansibility is made a trade-off for the deterioration of the frequency response. Is possible.

Summary of conclusions from this experiment As in the first and second experiments, this subjective test showed a significant increase in the impression of spatial spaciousness, which is the result of a monophonic system that made the speaker an inconvenient acoustic characteristic. Is. Frequency response measurements and calculations show that the composite loudspeaker according to the present invention can achieve a much better frequency response when the drive signal is at an appropriate level compared to a distributed mode loudspeaker alone.

Practical Embodiments As can be understood from the above discussion regarding experiments performed (both subjective testing and scientific measurements), the present invention presents the problem of emphasizing the spatial breadth of the sound generated by a speaker. Provides a practical and simple solution to the problem, specifically enabling the use of high-quality, wide frequency range piston-type speakers, and the wideness of the sound produced by the addition of distributed mode speakers Without any loss of high sound fidelity and the need for additional signal channels or complex signal encoding.

  In practicing the present invention, the distributed mode speaker and the piston type speaker must operate over the common part of the audible frequency band. The two speakers preferably operate over substantially the entire audible frequency band, for example, the piston type speaker may operate from 20 Hz to 20 kHz and the distributed mode speaker operates from about 100 Hz to 20 kHz. Or if the technology of distributed mode speakers develops further, the two speakers may operate over the entire audible frequency range (i.e., 20 Hz to 20 kHz). It is also within the scope of the present invention that a narrower frequency band is used depending on the situation such as cost and intended usage. For example, distributed mode speakers may be constrained to a much narrower frequency band compared to the band noted above, for example, frequency band 100 to 1,000 Hz, or frequency band 200 to 2,000 Hz, or maximum. There may be a frequency band that covers one or more octaves in the range up to 4,000 Hz or up to 6,000 Hz. As yet another specific example, the frequency band of one or more speakers in distributed mode may be from 100 to 6,000 Hz, and the frequency band of a piston type speaker may be from 800 to 8,000 kHz. It can happen.

  As another alternative, when a distributed mode speaker and a piston-type speaker operate over a common portion of the frequency range, the highest frequency of the piston-type speaker is substantially lower than the highest frequency of the distributed mode speaker, and the high frequency Then, the tweeter may be constituted by a distributed mode speaker.

  Thus, in general, the frequency range of a distributed mode speaker can be wider or narrower than the frequency range of a piston type speaker, and the lower end of the frequency range of the distributed mode speaker is at the end of the piston type speaker. May be higher or lower than the lower end of the frequency range, and the upper end of the frequency range of the distributed mode speaker is more than the upper end of the frequency range of the piston type speaker. May be higher or lower. The optimum frequency range for piston and distributed mode speakers may be determined experimentally depending on the application and cost, as well as the specific requirements in different usages and different markets.

  A number of practical embodiments of the invention will be described below. In most of these embodiments, a specific frequency will not be given. These should be taken as being selected from the ranges already shown in the above discussion, depending on the specific product situation to be designed according to the description of the embodiment.

  Furthermore, the arrangement of speakers or sound reproduction devices when using the following embodiments is not described. The user or system installer will determine the optimal location in any particular listening space. If the distributed mode speaker is a physically separate unit from the piston type speaker, the two speakers should be positioned next to each other, positioned on top of each other, or elsewhere (eg, listening to the distributed mode speaker). It may be positioned on the back side or side of the area prepared for the hand). In this connection, the placement of the speakers within the surround sound system is important and depends on the encoding of the signals on the different channels (encoding is performed assuming that the speakers are in a predefined position). It should be understood that this limitation does not apply to the present invention.

  In addition, tests may utilize the introduction of a delay between the output of piston-type and distributed mode speakers (not mentioned in the above description of the experiment), and specifically, for distributed mode speakers. It should also be understood that it is pointed out that the applied signal may be delayed with respect to the signal applied to the piston type speaker. When providing a delay, it should generally not exceed 80 msec, and preferably not exceed 35 msec. Informal tests have shown that the introduction of such delays emphasizes “imaging” or “localization” to sound in stereophonic and surround sound applications. These improvements in image formation and location improve musical intelligibility when listening to music.

  This improvement occurs because, as a result of the delay, the transient of the sound from the piston-type speaker is not masked by the distributed mode speaker, but the transient from the distributed mode speaker is masked by the transient from the piston-type speaker. It is considered to be done.

In the studies related to LEF and IACC, and in the studies related to the effects of delay, we give a theoretical explanation underlying this effect, but we understand that this application is not bound by these explanations Should. The explanation given here is based on the current knowledge and measurement technique in the audio field, but the psychoacoustic effect on the sound of humans is a very complex issue and an accurate explanation. It should also be understood that it is difficult (and impossible in some situations) to provide
A number of practical embodiments relating to the present invention will now be described.

First Embodiment FIGS. 8 to 12 show a stereophonic sound reproduction system according to a first embodiment of the present invention.

  As shown in FIG. 8, this system is equipped with a number of input devices 2, such as CD players, stereo FM tuners and / or stereo tape players, and a conventional configuration for reproducing stereophonic sound such as music. Therefore, a stereo acoustic amplifier unit 4 having a normal preamplifier, a control circuit and a power amplifier, and a pair of speaker units 6 respectively connected to the left and right channel outputs of the amplifier 4 are provided. . Each of the speaker units 6 includes both a conventional cone speaker and a distributed mode speaker that are driven in accordance with the teachings of the present invention. The two speaker units 6 are identical to each other.

  As shown in FIG. 9, each speaker unit 6 comprises a casing 8 containing a conventional full frequency range two-way cone speaker system with a base / midrange speaker 10 and a tweeter 12. ing. Each of the cone speakers 10 and 12 includes a respective electromagnetic drive unit that may be of the moving coil or moving magnet type to drive the respective cone. The casing 8 has a front surface, a back surface, a top surface, a bottom surface, and side panels 8a, 8b, 8c, 8d, 8e, and 8f. The front panel 8a has openings 14 and 16 for arranging the cones of the speakers 10 and 12 on the rear side. The cones of the loudspeakers 10, 12 close the openings 14, 16, thereby forming a closed chamber by the casing 8 in the same way as in the prior art, by placing the cone loudspeakers 10 and 12 therein. These speakers can generate sound in free air in a conventional manner. The interior of the closed chamber in the casing 8 may contain any conventional structure or damping material.

  The distributed mode speaker 22 is secured in the vertical direction at the top of the casing 8, and includes a speaker panel 24 and an electromagnetic actuator 26 attached to the back surface of the panel 24. The panel 24 is supported in a plane substantially the same as the front surface of the casing 8 by a rectangular frame 28 secured to the casing 8 along one edge 30, and the panel 24 is well-known by an actuator 26. It is supported in such a manner that it can be excited to produce resonant distributed mode vibration.

  The panel 24 and the frame 28 are positioned on the top surface of the casing 8 and form the front wall of the housing 32 such that its side, back and top wall 32a are all made from a metal mesh including a number of openings. As a result, the sound generated from the back surface of the panel 24 is substantially freely sent to the free air through the mesh wall 34.

  The exciter 26 includes a non-magnetic light weight and rigid cylindrical winding die 34, an electric coil 36 wound around the winding die 34 and supported by the winding die, and a magnet 38. All of these are represented by the schematic cross-sectional view of FIG. The magnet 38 is essentially cup-shaped and includes a circular end or bottom wall 38a, a cylindrical side wall 38b, and a solid cylindrical central core 38c. Between the outer surface of the central core 38c of the magnet 38 and the inner cylindrical surface of the winding mold 34, a soft compliant material 39 is applied by an adhesive to support the magnet compliant with the winding mold. As a result, when the coil 36 is energized by an AC electric signal, a relative vibrator motion is generated between the winding form 34 and the magnet 38 by the combined electromagnetic force acting between the coil 36 and the magnet 38. . As is known in the art for distributed mode speakers, the magnet is not supported except as described above, but because the magnet is substantially heavier than the former, the mechanical inertia of the magnet 38 due to this weight. As a result, vibration can be transmitted to the panel 24. As is well known in the art for distributed mode speakers, additional supports for the magnet 38 (such additional supports are not shown in FIG. 10 and are not included in this embodiment). However, this support must still allow the vibrator motion of the magnet.

  The panel 24 shown schematically in FIG. 10 includes an internal honeycomb structure 24a that includes passages extending from the front to the back of the structure, which are closed by front and back layers 24b and 24c, respectively. . This structure is chosen to be lightweight according to the design principle of the distributed mode loudspeaker and to be able to be set to resonant distributed mode vibration in the form of a bending wave by activation of the exciter 26 as already described above. The exciter 26 is suitably designed according to the design principles for distributed mode speakers and is positioned on the panel 24 for this purpose.

  As already pointed out, the panel 24 is compliantly mounted within the frame 28 to allow these vibrations. FIG. 11 shows a compliant mounting means suitable for this purpose (ie a soft foam strip 40 secured by adhesion between the edge region 24d of the panel 24 and the back surface 28a of the frame 28 (shown in L-shaped cross section)). An example is shown. The strip 40 is discontinuous in its interior so that the edge region 24e of the panel 24 can vibrate freely without adhering to the frame 24 at the location of the region 24e. In accordance with the design principles for the distributed mode speaker, the selection of the regions 24d and 24e of the panel 24 is performed to optimize the ability of the panel to be excited to oscillate in a resonant distributed mode.

  As represented schematically in FIG. 12, each speaker unit 6 is for connection via appropriate wiring to the output of the conventional amplifier 4 shown in FIG. 8 and cone speakers 10 and 12 and A pair of input terminals 42 are provided for supplying drive signals to the distributed mode speaker 22. These signals are fed to each of the woofer and tweeter cone speakers 10 and 12 through a low-pass filter 44 and a high-pass filter 46 that together form a conventional crossover circuit, and further higher It is supplied to the distributed mode loudspeaker 22 via a band pass protection filter / attenuation circuit 48. The cone speakers 10 and 12 and the filters 44 and 46 are capable of reproducing substantially all of the audible frequency range (ie, 20 Hz to 20 kHz) with the speakers 14 and 16 together, thereby providing a conventional cone speaker speaker. Designed and arranged so that the system can be configured. A distributed mode speaker 22 that includes a high-pass protection filter in circuit 48 takes into account that, in the current topology, the distributed mode speaker is practically unable to reproduce sound at least generally less than 100 Hz in frequency. And designed and arranged to generate as much of the full frequency range as possible. Therefore, the circuit 48 is arranged so that a signal having a frequency of less than 100 Hz is cut off and the distributed mode speaker 22 can reproduce a frequency within the range of 100 Hz to 20 kHz. An attenuator is included in this circuit 48 so that the distributed mode speaker 22 can generate a sound pressure level below the sound pressure level generated by the cone speakers 14 and 16. For example, a sound pressure level of −5 db + 3 db or −3 db is a preferred sound pressure level difference (as described above with respect to the content of the experiment performed).

  Thus, the embodiment of FIGS. 8-12, when manufactured from components of appropriate quality, is simply a tweeter in combination with a conventional speaker alone, a distributed mode speaker alone, or a conventional speaker used as a woofer. It is possible to provide a high-fidelity music reproduction system in which the space expanse is further improved as compared with the space expanse obtained by the arrangement used as the device.

  The high pass protection filter / attenuator circuit 48 is preferably adjustable by the user so that the user can set different levels of attenuation by trial and error depending on their preferences and room acoustic characteristics, and the circuit further comprises a distributed mode. The signal applied to the speaker is preferably adjustable so that it can be introduced with a delay in the range of 0-35 msec.

  In use, the speakers of the system described with reference to FIGS. 8-12 may be positioned in a conventional manner, but as much as possible to ensure that the distributed mode speakers can radiate not only forward but also backwards. Should not be placed directly against the wall or anything else that would impede the back propagation of sound from the distributed mode speaker.

Second Embodiment FIG. 13 shows a conventional high fidelity music playback system comprising a conventional input device, a conventional stereo amplifier, and a pair of conventional cone speakers 50 as described above. An alternative to the present invention as assisted by a pair of auxiliary sound playback units 52, one for the right channel and one for the left channel, which converts a high fidelity system into a system in accordance with the teachings of the present invention. 2 represents a typical embodiment.

  Each auxiliary unit 52 has a distributed mode speaker 54, a signal conditioning processing amplifier 56 having an input terminal 58 connected to each one of the left and right speaker outputs of the amplifier 4, and a respective distributed mode speaker 54. And an output terminal 60 connected thereto. Each signal conditioning amplifier 56 is supplied with main power as indicated by reference numeral 62. For convenience, each input terminal 58 is connected to the terminal of the speaker unit 50 with a short wiring length, so that an additional long wiring is connected between the output of the amplifier 4 and the input of the auxiliary unit 52. It can be avoided.

  FIG. 14 is a block diagram of each signal adjustment processing amplifier 56. As shown in the figure, an attenuator 64 is connected to an input terminal 58, and this attenuator 64 supplies a signal to a digital control type volume control circuit 66. The power is supplied to the power amplifier 70 via the equalizer 68, and the output of the power amplifier 70 is connected to the terminal 60.

  The attenuator 64 includes a high resistance resistor 72 connected across terminals 58 having taps 74 for supplying a signal referred to above as a low level signal to the digital volume control 66. The resistance value of the resistor 72 is such that the total impedance generated by connecting both the signal conditioning processing amplifier 56 and the speaker 50 between the output terminals of the amplifier 4 is as close as possible to the impedance provided when the speaker 50 alone is provided. This value is selected so that the amplifier 4 is not adversely affected by being connected to the auxiliary unit in addition to the conventional cone speaker 50.

  The 7 band equalizer includes a number of preset controls 68a for presetting the relative amplification applied in 7 different frequency bands. The setting of the control 68a is at least partially compensated for any variation in the frequency response of the distributed mode speaker 54, as well as satisfactory playback is not possible with the distributed mode speaker, such as frequencies below 100Hz. Chosen to cut off any low frequency.

  The microcontroller 76 controls the digital volume control circuit 66, the equalizer 68 and the power amplifier 70. Microcontroller 76, on the other hand, is a manual volume control device 78 that is operable by signals from an infrared detector 80 to adjust volume in response to the system user as well as a handheld remote control device (not shown). This allows the system user to adjust the volume of the sound generated by the distributed mode speaker relative to the volume generated by the cone speaker. To avoid wasting power, device 56 is made to enter a power down mode when no signal is supplied from amplifier 4. The input detector circuit 82 is connected to the tap 74 and provides a control signal to the microcontroller 76 in response to detecting a signal appearing at the location of the tap 74 so that the microcontroller 76 operates the circuit. It is programmed to enter the power-up mode, which is the current mode.

  In the embodiment of FIGS. 13 and 14, the conventional cone speaker 50 operates over the entire frequency range, and the distributed mode speaker 54 is as wide as possible within that range as previously discussed in connection with the above embodiment. Operating over a range, and as a result, an existing system is invented by adding a pair of auxiliary units to an existing high fidelity sound reproduction system as described with reference to FIGS. And can be converted to an improved system that provides improved space expansibility.

  Therefore, since the auxiliary unit 52 is manufactured and sold as a whole separately from the high fidelity system, it can be added to the existing high fidelity system. The signal conditioning processing amplifier 56 may be physically mounted on or in the base or housing that supports the distributed mode loudspeaker, or alternatively may be separated therefrom.

  Further, although FIG. 13 represents two separate signal conditioning processing amplifiers 56, an input attenuator 64, a digital volume control 66, and an equalizer 68 are alternatively provided for a two channel signal conditioning processing amplifier. It is also possible to provide a channel with a power amplifier 70 already shown as a single microcontroller controlling these two channels. In such an arrangement, the input detector is connected to these two input attenuators and arranged to cause the circuit to enter power-up mode in response to signals on one or both of the channels. Has been. Such a two-channel signal conditioning processing amplifier may have all its components contained within a single housing, these components being the base or support for one of the distributed mode speakers. It may be built into the housing, or alternatively may be manufactured separately from the distributed mode speaker. Providing a single microcontroller further reduces costs.

  In order to simplify the connecting operation of the auxiliary units 52 to the existing sound reproduction system as much as possible, each auxiliary unit 52 is directly connected to the input terminal 58 and has an existing conventional cone with a short wiring length (not shown). An additional output terminal (not shown) for connection to the speaker may be provided, which may be included in the auxiliary unit during manufacture and sale. In the modified embodiment provided with a two-channel signal conditioning processing amplifier as described above, there will be two sets of such additional output terminals, one for each channel.

Third Embodiment FIG. 15 is a diagram for enabling a signal conditioning processing amplifier to receive input at a line level as well as at a high (speaker) level (similar to the arrangement of FIG. 14). Represents a modification to the input end of the circuit shown in FIG. For this purpose, a line level input terminal 82 is provided which is connected to one input of the input switch 84, and the other input is connected to the output of the attenuator 64. The input detector circuit 80 is replaced by a detector circuit 86 having two inputs, one connected to the tap 74 and the other connected to the line input 82. The input detector circuit 86 is arranged to send a signal to the microcontroller 76 indicating that a signal has appeared at the position of the line input 82 or tap 74, and the microcontroller interprets this signal and inputs it. The switch 84 is appropriately set so that its output is connected to either the line input or the tap 74. As described with reference to FIG. 14, the microcontroller further causes the circuit to enter a power-up mode in response to a signal from the input detector 86.

  As in the embodiment of FIG. 14, both the left and right channels can be provided within a single unit and controlled by a single microcontroller, as already described. is there.

  Further, as described above, in order to simplify the connecting operation of the auxiliary unit to the existing sound reproduction system, there is an additional connection directly connected to the input terminal 58 and for connection to the conventional cone speaker 50. An output terminal may be provided.

Fourth Embodiment FIG. 16 represents an alternative form of auxiliary unit for converting a conventional high fidelity system into an embodiment of the present invention. In FIG. 16, this conventional high fidelity unit comprises an input device 2 and a conventional amplifier 4 and a pair of conventional cone speakers 50 (in this embodiment compared to a distributed mode speaker added to the system). (Assuming high efficiency). Accordingly, FIG. 16 shows a distributed mode speaker 54, each connected to an input terminal 90, and an attenuation connected between the input terminal 90 and the output terminal 94 for connection to a conventional cone speaker 50. And left and right auxiliary units 88 comprising a circuit 92.

  The arrangement shown in FIG. 16 assumes that when all the speakers are connected, the impedance between the terminals 90 falls within the range of impedance that can be handled by the amplifier 4.

Fifth Embodiment FIG. 17 is an arrangement similar to that shown in FIG. 16 except that the arrangement assumes that the distributed mode speaker 54 is more efficient than the cone speaker 50. Thus, the attenuator circuit 92 is not connected between the input terminal 90 and the output terminal 94 but between the input terminal 90 and the distributed mode speaker 54. As in the case of FIG. 16, in FIG. 17, it is assumed that the total impedance between the terminals 90 when all the speakers are connected is within the impedance range that the amplifier 4 can handle.

Sixth Embodiment Referring to FIG. 18, the sound reproduction system includes a conventional input device 2 as described above, and first and second left channel stereo output terminals 102, 104 connected to a distributed mode speaker 106. And the first and second right channel stereo output terminals 110, 112 are connected to the distributed mode speaker 114 and the conventional cone speaker 116, respectively. And a stereo acoustic amplifier 100 constructed according to purpose. Both conventional cone speakers 108 and 116 are preferably full frequency range speakers, and are, for example, two-way or three-way devices with a conventional crossover circuit, where these cone speakers cooperate. May play sounds within this range (ie, 20 Hz to 20 kHz). Further, as described above, the distributed mode speakers 106 and 114 cover the widest possible range of the entire range to produce sound in the range of at least 100 Hz to 20 kHz as described above.

  As shown in FIG. 19, amplifier 100 includes a conventional input selector circuit 118 having left and right output terminals 120, 122 for receiving user-selected inputs from conventional device 2, respectively. The left output terminal 120 is connected to the input terminals of both a left distributed mode speaker signal processing channel 124 and a left cone speaker signal processing channel 126 whose outputs are connected to terminals 102 and 104, respectively. The right output terminal 122 of the input selector 118 is connected to the inputs of both a right distributed mode speaker signal processing channel 128 and a right cone speaker signal processing channel 130 whose outputs are connected to terminals 110 and 112, respectively. Yes.

  Channels 124, 126, 128, and 130 are controlled by microcontroller 132 that receives control input from a set of conventional control 136 and relative volume control 140. The conventional control 136 is arranged to be actuated by the user of the system and may include all of the normal controls such as left / right balance control, treble and bus control, graphic equalizer control, etc. The relative volume control 140 is further arranged to receive user actuation and sets the relative volume between the distributed mode speakers 106 and 114 on the one hand and the conventional cone speakers 108 and 116 on the other hand. Is for.

  Each of the distributed mode speaker channels 124 has a digital volume control, a 7 band equalizer with presets, and the same power as components 66, 68, 68a, 70 as described with reference to FIG. And an amplifier. Each of the cone speaker channels 126 and 128 is conventional for driving conventional cone speakers as appropriate or desired, such as conventional filters, volume control (in this case digitally controlled), power amplifiers and graphic equalizers. An expression circuit is provided.

  The conventional control 136 controls the four channels 124, 126, 128, 130 to generate the requested output according to the settings (volume, filtering, equalization, etc.) of the conventional control 138. Relative volume control 140 adjusts the relative power levels of signals applied to terminals 102 and 110 on the one hand and terminals 104 and 112 on the other hand, thereby generating volume or sound pressure generated by conventional cone speakers 108 and 106. The volume or sound pressure level generated by the distributed mode speakers 106 and 114 can be adjusted with respect to the level, preferably the output of the distributed mode speaker relative to the output of a conventional cone speaker as described above. Can be set to -5 decibels ± 3 decibels, and further possible settings are provided to further take into account user preferences, room acoustics and the characteristics of the speakers used.

  Thus, according to this embodiment, the first and second left channels and the first and second right channels for implementing the present invention with a simple connection to the distributed mode speaker and cone speaker as described. A novel stereo acoustic amplifier is provided.

Seventh Embodiment FIG. 20 is a block diagram of another embodiment of the present invention comprising a self-contained sound playback device 142. Self-contained device 142 includes first and second left line level connector sockets 143 and 144 for connection to an active distributed mode speaker 145 and an active conventional cone speaker 146, respectively, And first and second right line level connector sockets 147 and 148 for connection to speaker 149 and active conventional cone speaker 150, respectively. The word “active” in relation to a speaker, both conventional and illustrated in the drawing, is provided with a built-in power amplifier, which allows the speaker to reproduce sound from a line level signal. Means that is possible.

  The self-contained playback device 142 includes one or more stereo signal sources 151 (eg, FM radio tuners and / or compact disc players) whose left and right outputs are provided to the left and right channels 152 and 153, respectively. Is included. Each of these channels has an output terminal connected to the input of the relative volume control circuit 156, the input of the main power amplifier 157, and the output socket 144 in the case of the left channel or the output socket 148 in the case of the right channel. A volume control 154 having 155 is provided. The device 142 includes left and right conventional built-in cone speakers 158 and is connected to the output of the power amplifier 157 via respective switches 159. The connectors 143, 144, 147, 148 are preferably standard sockets for receiving standard plugs. Mechanical connections are provided between sockets 144 and 148 to switch 159, respectively, and when a plug (not shown) is inserted into these sockets, these switches are opened to disconnect the built-in speaker. be able to.

  A main volume control device 160 that receives an operation by a user controls the main volume control circuit 154 of these two channels simultaneously. In order to adjust the relative volume control circuit 156 to adjust the output of the distributed mode speaker with reference to the output of the cone speaker, a control element for user operation such as a knob is provided. In this embodiment, each of the two relative volume control circuits has its own individual user-operated control element, which allows the distributed mode and cone speakers in the left and right channels, respectively. The relative volume can be adjusted individually. If desired, this circuit may be modified to provide a single relative volume control element that is actuated by the user to adjust each relative volume of the left and right channels simultaneously.

  The frequency range reproduced by speakers 145, 146, 149 and 150 is as described above for distributed mode speakers and conventional cone speakers, and the relative volume has already been described elsewhere in this specification. It is preferable to be able to adjust as described above.

  As will be apparent from the description of FIG. 20, distributed mode speakers 145 and 149 are used either in combination with external cone speakers 146 and 149 or in conjunction with built-in speakers 158. can do.

  The self-contained sound playback device 142 may be in the form of a portable device such as a portable radio, portable CD player, or portable radio / CD player, for example, a television receiver sound system or portable -It may be a computer sound system such as a computer.

Eighth Embodiment The embodiment of FIG. 21 is similar to that of FIG. 20 except that the built-in speaker 158, main amplifier 157 and switch 159 (and associated mechanical links to sockets 144 and 148) are omitted. This is the same as the embodiment.

Ninth Embodiment FIGS. 22 and 23 are driven through an amplifier unit 164 by a conventional portable player 165, such as a CD player or tape player, having line level outputs 166 and 167 for left and right channels, respectively. One of the present invention comprising a left distributed mode speaker and a conventional cone speaker as described with reference to FIG. 18 and a right distributed mode speaker and a conventional cone speaker 106, 108, 114 and 116. 1 represents an embodiment.

  The amplifier unit includes a housing containing left and right channel buffer amplifiers 169, 170, first and second left channel power amplifiers 171, 172, and first and second right channel power amplifiers 173 and 174. 168. Left and right channel input leads 175 and 176 are connected by conventional plugs 177 and 178 to line level outputs 166 and 167, respectively, and the left and right line level signals generated by portable player 165 are supplied to buffer amplifiers 169 and 170, respectively. Supplying to each of the inputs. Left channel power amplifiers 171 and 172 independently amplify the signals generated by buffer amplifier 169 to drive each of distributed mode speaker 106 and conventional cone speaker 108 via terminals 179 and 180, respectively. . Similarly, right channel power amplifiers 173 and 174 provide the signals supplied by buffer amplifier 170 to drive right distributed mode speaker 114 and right conventional cone speaker 116 via terminals 181 and 182, respectively. Amplifying.

  The four power amplifiers 171, 172, 173, 174 include respective volume control circuits so that the four speaker outputs can be individually adjusted. In this embodiment, the frequency range in which the distributed mode speaker and the conventional cone speaker are operated is as described above, and the sound pressure output between the distributed mode speaker and the conventional cone speaker is as described above. The difference is also adjustable within the range described above.

  Thus, amplifier unit 164 uses a conventional stereo player with line level output by adding two conventional cone speakers and two distributed mode speakers external to the conventional stereo player. Thus, the present invention can be realized. The amplifier unit may be manufactured and sold separately from the other components. They may be sold with or without connecting leads.

  The individual plugs 177 and 178 illustrated in FIGS. 22 and 23 are, in one modification, replaced with standard stereo plugs such as “mini plugs” if a conventional socket of the type acceptable to the player is provided. Sometimes.

Tenth Embodiment FIG. 24 shows another embodiment of the present invention in the form of a self-contained sound playback device. This device comprises a housing, shown schematically at reference numeral 185, which contains all the components necessary for the implementation of the present invention. Thus, housing 185 includes left and right two-way conventional speakers with left and right distributed mode speakers 186, 187, each with tweeters 188a and 189a, woofers 188b and 189b, and conventional crossover circuits 188c and 189c. Cone speaker systems 188 and 189. One or more stereo signal sources, together with the required control and speaker drive circuitry, are indicated generally by the reference numeral 190, which are also contained within the housing 185 and are volume, balanced, Normal user-actuated controls such as treble and bus control are provided. The signal channels for driving and controlling the distributed mode speaker and the conventional cone speaker may be similar to those described above, and thus the volume levels of the distributed mode speaker and the conventional speaker are set to each other. It may include both global volume control and relative volume control to adjust relative to.

  As in the above embodiment, the frequency range generated by the distributed mode speaker is substantially the same as or preferably the same as the frequency range generated by the conventional cone speaker. However, in the case of a self-contained portable device, its frequency range may be smaller than in a high fidelity system, for example for use at home. The self-contained device 185 can take any of a variety of different forms, such as a portable radio and / or CD and / or tape player, television receiver or portable computer. When the present invention is embodied in a computer, some or all of the control may be realized by software.

Eleventh Embodiment The present invention can be used in a so-called “surround sound” system. FIG. 25 shows an example of such an implementation.

  Referring to FIG. 25, a conventional surround sound input device 191 has five channels each connected to a different speaker 6 positioned at an appropriate location in the listening room (ie, left, center and right front). And a conventional surround sound amplifier 192 having left and right side channels). Each of the speakers 6 is the same as that described in detail with reference to FIGS. 9 to 13 so that the present invention can be realized in a surround sound system.

Embodiments of the present invention in a digital piano It is well known that even the best quality digital pianos currently available, the sound produced is fairly unmusical. By embodying the teachings of the present invention in a digital piano, it is possible to generate a more realistic music sound from the digital piano. Specifically, the digital piano according to the present invention is similar in quality to the sound of a high-quality acoustic grand piano for the listener when the piano is manufactured to an appropriate quality. It is possible to generate a very rich sound with a random component that gives the impression. This can be achieved at a much lower cost compared to the cost of a top quality acoustic piano.

Grand Piano FIG. 26 is a perspective view of a digital grand piano according to an embodiment of the present invention. The piano includes a casing 200 having a conventional hinged lid 202 that is supported on a leg 201 and illustrated in a open position by a conventional branch line 203. A conventional type keyboard 204 and a set of pedals 205 used in a digital piano that performs normal functions are supported in a normal position by a casing 200. This piano (as already known in the field of digital piano technology) is a traditional high quality grand piano action connected to the keyboard to give the performer a good concert grand feel. (Not shown) is preferably included.

  The casing 4 has two speaker assemblies 210 each comprising a tweeter 216, a midrange unit 214 and a subwoofer 218 arranged to align with the treble, midrange and base portions of the keyboard, respectively. 212 is supported. Each of the speakers 216, 214, and 218 is a conventional electromagnetically driven cone that is positioned so that the cone is oriented vertically upward and the sound produced thereby is reflected by the piano lid.・ Speaker. This orientation is particularly preferred for tweeters and mid-range speakers, but the orientation of the subwoofer is less important.

  The casing 4 further supports two distributed mode speakers 220 and 222 that are positioned horizontally to radiate sound upward and downward. As an example, the panels of the distributed mode speakers 220, 222 may have dimensions of 700 × 500 mm.

  It should be understood that the speaker arrangement shown in FIG. 26, where conventional speakers are grouped near the keyboard and the distributed mode speakers are separated from the keyboard, is merely exemplary. Alternatively, conventional and distributed mode loudspeakers may be placed alternately or in a position opposite to that shown in the drawings. In addition, the tweeters, midrange units, and subwoofers of conventional speaker assemblies may be separated and interleaved with distributed mode speakers.

  As shown in FIG. 27, MIDI generated in response to a signal from the foot pedal switch 206 and a signal from an infrared pickup 207 (not shown in FIG. 26) disposed on the lower side of the piano keyboard 204. The first and second audio signal generators 230 and 2 are arranged to respond to the MIDI signal and the foot pedal switch 107 to generate an acoustic signal that duplicates the grand piano sound. It is sent to the audio signal generator 231. The first and second generators 230, 231 may be implemented by a conventional computer including software known for this purpose.

  In this embodiment, the first audio signal generator 230 comprises a first high quality sample library 232 and a first sound module 234. The second audio signal generator includes a second high quality sample library 237, a second sound module 238, and a physical modeling unit 239. Each library 232 and 237 contains digital samples recorded from a different high quality grand piano (preferably a concert ground). Thus, for example, the first sound sample library 232 may include a 1.6 Gb Steinway sample library, and the second sample library 237 may include a Yamaha 30 Mb sample sound library. Sound modules 234, 238 include a software program for selecting sound samples from sound libraries 232, 237 in response to received MIDI signals and signals from foot pedal switch 107. The second audio signal generator 231 was further selected by the second sound module 238 because the second sample library 237 (in this embodiment) is much smaller than the first sample library 232. A physical modeling unit 239 arranged to modify the sound samples in a conventional manner is included.

  The acoustic signal from the generator 230 is amplified by the amplifier 240, and the amplified signal drives the two corresponding to the two distributed mode speakers 220, 222.

  The acoustic signal from generator 231 is amplified by amplifier 245 and further fed to crossover unit 247 for driving two conventional speakers 210, 212. The crossover unit 247 sends high frequency, mid-range and low frequency signals to the tweeter 216, woofer 214 and base 218 of the conventional speakers 210, 212, respectively, in a conventional manner.

  The cone speaker reproduces sound over substantially the entire audible frequency range (ie, 20 Hz to 20 kHz, or 45 Hz to 20 kHz). This distributed mode speaker generates sound over as much of this range as possible (ie, 80 Hz to 20 kHz, or 100 Hz to 20 kHz). The sound pressure level provided by the distributed mode speaker is again the same as described above, or according to the acoustic characteristics of the music hall or listening room where the piano is played, May be adjusted to be lower than the generated sound pressure level, and the output of the distributed mode speaker has substantially the same sound pressure level as the sound pressure level of a conventional cone speaker Or it may have a higher sound pressure level. In order to be able to change the sound pressure level of the distributed mode speaker independently of the sound pressure level of the conventional cone speaker, it is preferable to provide independent volume control for the distributed mode speaker and the cone speaker. These are not shown in the drawing.

  When the piano is being played, the distributed mode speaker and the conventional speaker are driven simultaneously. The result is complexity and richness due to the combination of different air turbulence patterns propagating to each of the distributed mode and conventional cone speakers, and the interaction between the different patterns changing randomly. An air turbulence pattern is generated, which can produce a substantially richer sound than if either type of loudspeaker would individually generate. Furthermore, this richness is emphasized in the sense that the signal used to drive a distributed mode speaker is different from the signal used to drive a conventional speaker.

  Furthermore, as described in connection with the above experiments, this combination of distributed mode loudspeaker and conventional cone loudspeaker achieves an improvement in spatial spaciousness.

  In this embodiment, samples from two different models of the grand piano are used, but samples from three or more different grand pianos (in this case, different speakers of the speakers are derived from different sets of samples, respectively). Further richness can be achieved by utilizing (which may be driven by the signal generated). In addition, samples other than Steinway and Yamaha samples may be used, and the sound libraries used will both include the maximum number of samples currently available taking into account the latest technology. (And preferably in the case of the highest quality equipment). More specifically, as the amount of computer memory increases and costs decrease, it becomes possible to provide a sound library that contains more and more samples, thus potentially improving the quality of the sound. is there.

Digital Upright Piano Referring to FIG. 28, a digital upright that may produce a lower quality sound than the sound produced by the pianos of FIGS. 26 and 27, but may be less costly. The piano includes a casing 251 having a back panel 252 that supports a pair of distributed mode speakers 253 and a pair of conventional cone speakers 254. In this embodiment, unlike the above embodiment, only two cone speakers are provided to reduce cost. The distributed mode speaker 253 is provided in a direction parallel to the surface of the back panel 252 of the casing 251. The cones of the two conventional speakers 254 are oriented so that the cone axis is orthogonal to the surface of the back panel 252.

  FIG. 29 is a block schematic diagram of the piano of FIG. Unlike the above embodiment, only a single audio signal generator 230 with a sound library 262 and a sound generation module 260 is provided for cost savings. The generator 230 generates an acoustic signal using the sound library 262 based on the signals received from the infrared pickup 207 and the foot pedal switch 207.

  As in the case of the above embodiment, the distributed mode speaker 253 and the conventional cone speaker 254 are arranged to be simultaneously driven through the amplifiers 245 and 247, and the distributed mode speaker 253 with respect to the electronic piano. And an air turbulence pattern, which is the synthesis of the sound output by the conventional speaker 254, can be generated, thereby making the analogy to the sound propagation generated by an acoustic device as described above closer. Further, as is apparent from FIG. 29, these two cone speakers 254 are identical and therefore assume a relatively limited frequency range and therefore do not include any crossover circuitry. The frequency range of the distributed mode speaker should overlap as much as possible with the frequency range of the conventional cone speaker to emphasize the spaciousness of the sound as discussed above in connection with the experiment. The sound quality produced by the embodiment of FIGS. 28 and 29 cannot be comparable to the sound quality produced by the embodiment of FIGS. 26 and 27, but with appropriate component quality, FIG. Even 29 embodiments can achieve higher overall quality compared to many currently available digital pianos.

  A modification to the circuit of FIG. 29 is illustrated in FIG. 30 to provide certain additional improvements. In this figure, the acoustic signals generated by the generators 230 and 260 are sent to a signal correction unit 265 such as a digital signal processing unit, and this signal correction unit 265 is sent to an amplifier 247 that drives a cone speaker 254. A corrected signal is generated. The signal modification unit 265 may be arranged to change the timing and sound quality of the acoustic signal output by the sound generation unit 260. The signal modification unit 265 includes a conventional user interface (not shown) that allows the user to select a method for modifying the signal output by the sound generation unit 260. According to this method, since the quality of the signal for driving the cone speaker is different from the quality of the signal for driving the distributed mode speaker, the richness of the sound can be emphasized to some extent. If desired, additional signal modification units can be placed between the sound generation module 260 and the amplifier 245 that drives the distributed mode loudspeaker to further introduce richness.

  In the above three embodiments, it has been described that sound is output through a pair of distributed mode speakers and a pair of conventional speakers, but similar random mixing for air turbulence patterns is a single It should be understood that this can be achieved by simultaneously outputting sounds corresponding to the same sound through a distributed mode speaker and a single cone speaker.

  In the above embodiment, the infrared motion detection system for detecting key movement has been described as utilizing infrared motion detection, but other means are used to detect key presses. For example, it is possible to use an electromechanical motion detection system to detect the position, pressure and speed of key activation.

Auxiliary units for digital pianos Many people already have their own digital pianos. FIG. 31 shows a conventional digital piano 300 connected to an auxiliary unit 302 to form a piano embodying the present invention.

  As can be seen in FIG. 4, the auxiliary unit 302 generates an audio signal connected to the MIDI signal output 314 via a cable 310 and plug 312 conventionally provided on a digital piano currently available. A distributed mode speaker 304 driven by an amplifier 306 that receives a signal from a receiver (similar to that described above).

  The conventional digital piano 300 includes a three-way conventional cone speaker system 316 with a woofer 318, a midrange unit 320 and a tweeter 322. Operated to be driven through a conventional crossover circuit (not shown), thereby generating substantially all frequencies in the audible frequency range (ie, 20 Hz to 20 kHz). Distributed mode speaker 304 is operable to generate frequencies that span a substantial portion of the frequency range (eg, 100 Hz to 20 kHz) generated by speaker system 316.

  Although not shown in FIG. 31, a conventional digital piano 300 typically operates using a sound library of samples recorded from a good concert ground. The audio signal generator 230 also includes a sound library that preferably contains samples recorded from another model of a good concert ground for the reasons described in connection with the embodiments of FIGS. .

  The auxiliary unit 302 may be manufactured and sold separately from the digital piano so that it can be connected to an existing digital piano owned by the purchaser. Simply connecting the auxiliary unit 302 to the existing MIDI output of a digital piano, as well as the volume control of the digital piano, in addition to the sound generated by the distributed mode speaker 304, the sound is transmitted by the conventional speaker system 316. The benefits of the present invention can be achieved by ensuring that it is set to a level such that it is generated.

Variations and Modifications As can be appreciated from the above description, the present invention can be embodied in a wide variety of ways. Many other modifications or variations on the above may also be within the spirit of the invention.

  For example, the present invention may be embodied in a public loudspeaker system, a sound system in a theater or movie theater, an in-vehicle entertainment system, or a surveillance system in a recording or broadcast studio.

  In addition to digital pianos, the present invention may be used to reproduce sound from another electrical or electronic acoustic device such as an electric guitar.

  Each of the embodiments described and illustrated above utilizes a conventional cone speaker, but in at least certain situations, it is alternatively mounted to drive vibrator motion and driven by a piezoelectric transducer. Alternative forms of piston type loudspeakers such as electrostatic loudspeakers or piezoelectric loudspeakers with flat panels and membranes to receive are also possible. However, in most situations, an electromagnetically driven cone speaker is preferred.

  Although stereophonic devices are illustrated in all of the sound reproduction device embodiments of FIGS. 8-24, any of these embodiments can be modified to a single channel mono device. As already explained, the effect of the present invention is also achieved in mono applications.

  In the above, the introduction of a delay in the signal applied to the distributed mode speaker relative to the signal applied to the piston type speaker has been described. This delay can be provided in any of the embodiments described with reference to the drawings and in any other embodiment. Where a delay is provided, this is preferably adjustable by the user to suit the circumstances in which the invention is deployed.

  Furthermore, it is possible to provide additional similar processing to provide, for example, reverberation, equalization, or another effect on the signal applied to the distributed mode and / or piston-type speaker.

  In the above description of many embodiments, various preferred frequency ranges and relative power levels have been provided. It should be understood that these are merely examples and many variations are possible. However, it is important that the frequency range of one or more speakers in distributed mode overlap with the frequency range of one or more piston-type speakers. Furthermore, in many cases (especially the sound reproduction system embodying the present invention), the sound pressure level of the distributed mode speaker is slightly lower than the sound pressure level of the cone speaker (for example, a difference of several decibels) Will achieve optimal results, but an improvement is achieved when the distributed mode loudspeaker produces a substantially lower sound pressure level compared to the cone loudspeaker ( However, of course, the pressure level of a distributed mode speaker is not so low that the sound it generates is not perceptible). In these experiments, perceivable improvements are still achieved (although at a minimum at this level) by reducing the sound pressure level of the distributed mode speaker to as low as -35 dB relative to the cone speaker. The

  In certain situations, it is desirable to make the sound pressure level generated by the distributed mode speaker greater than the sound pressure level generated by the piston type speaker.

Claims (75)

  The step of simultaneously driving the distributed mode speaker means and the piston type speaker means with an electrical signal representing the sound to be reproduced, wherein the frequency range in which the distributed mode speaker means and the piston type speaker means operate is at least an audible frequency range. A sound generation process that includes driving processes that overlap within a part.   The process of claim 1, wherein the distributed mode speaker and the piston type speaker operate over substantially the same frequency range range.   The process of claim 1, wherein the distributed mode speaker operates over a narrower range than the piston type speaker.   The process according to claim 3, wherein the frequency range of the distributed mode speaker is entirely within the frequency range of the piston type speaker.   The process of claim 1, wherein the distributed mode speaker operates over a frequency range of at least 100 to 1,000 Hz.   The process of claim 1, wherein the distributed mode speaker operates over a frequency range of at least 200 to 2,000 Hz.   The process of claim 1, wherein the distributed mode speaker operates over a frequency range whose upper limit is not less than 6,000 Hz.   The distributed mode loudspeakers are separated by a frequency band in which the distributed mode loudspeakers do not operate over that band, and at least one of them overlaps at least a portion of the frequency range of the piston type loudspeaker. The sound generation process of claim 1, wherein the sound generation process is operating over a second frequency range.   9. The process according to claim 1, wherein a sound pressure level generated by the distributed mode speaker means is smaller than a sound pressure level generated by the piston type speaker means.   10. The process according to claim 9, wherein the sound pressure level generated by the distributed mode speaker means is smaller by 5 ± 3 decibels than the sound pressure level generated by the piston type speaker means.   11. A process according to any one of the preceding claims, wherein the sound generated by the distributed mode speaker means is delayed compared to the sound generated by the piston type speaker means.   The process according to claim 11, wherein the delay does not exceed 80 msec.   The process according to claim 12, wherein the delay does not exceed 35 msec.   The process according to any one of claims 1 to 13, wherein the distributed mode speaker means is designed using a mathematical calculation relating to the behavior of the distributed mode speaker means based on a selected value of the design parameter. process.   15. The process according to claim 1, wherein the sound is reproduced from a recording signal or a broadcast distribution signal.   16. Process according to any one of the preceding claims, carried out in a single channel for generating mono sound.   The process according to any one of the preceding claims, wherein the process is performed simultaneously on two channels to reproduce stereophonic sound.   The process according to any one of claims 1 to 15, being performed simultaneously on each of the channels of the surround sound system.   The process according to any one of claims 1 to 18, being carried out in a vehicle or a transport ship.   The process according to claim 1, wherein the process is performed in a domestic environment.   A speaker assembly comprising a piston-type speaker and a distributed mode speaker and circuit means for driving the speaker with an electrical signal representative of the sound to be reproduced, wherein the speaker is at least part of an audible frequency range. Speaker assembly designed to operate over overlapping frequency ranges.   24. The assembly of claim 21, wherein the distributed mode speaker and the piston type speaker are operable over substantially the same frequency range range.   The assembly of claim 21, wherein the distributed mode speaker is operable over a narrower range than the piston type speaker.   24. The assembly of claim 23, wherein the frequency range of the distributed mode speaker is entirely within the frequency range of the piston type speaker.   The assembly of claim 21, wherein the distributed mode speaker is operable over a frequency range of at least 100 to 1,000 Hz.   The assembly of claim 21, wherein the distributed mode speaker is operable over a frequency range of at least 200 to 2,000 Hz.   The assembly of claim 21, wherein the distributed mode speaker is operable over a frequency range whose upper limit is not less than 6,000 Hz.   The distributed mode loudspeakers are separated by a frequency band in which the distributed mode loudspeakers do not operate over that band, and at least one of them overlaps at least a portion of the frequency range of the piston type loudspeaker. 23. The assembly of claim 21, wherein the assembly is operable over a second frequency range.   29. Assembly according to any one of claims 21 to 28, wherein the distributed mode speaker means is designed to generate a sound pressure level that is smaller than the sound pressure level generated by the piston type speaker means. .   30. The assembly of claim 29, wherein the distributed mode speaker means is designed to generate a sound pressure level that is 5 ± 3 decibels lower than the sound pressure level generated by the piston type speaker means.   31. An assembly according to any one of the preceding claims, including means for delaying the sound generated by the distributed mode speaker means relative to the sound generated by the piston type speaker means.   The assembly of claim 11, wherein the delay does not exceed 80 msec.   The assembly of claim 12, wherein the delay does not exceed 35 msec.   34. A mono-acoustic sound reproduction system comprising at least one signal source, amplifier means, and a speaker assembly according to any one of claims 21 to 33 designed to be driven by the amplifier means.   34. First and second speaker assemblies according to any one of claims 21 to 33, and first and second connected to the first and second speaker assemblies for driving the speakers. Stereo sound type sound reproduction apparatus provided with the stereo acoustic type amplifier provided with these channels.   A keyboard, a pedal, means for generating an electrical signal representing a piano sound in response to activation of the keyboard and pedal, and any one of claims 21 to 33 designed to be driven by the electrical signal. A digital piano comprising the speaker assembly according to the item.   34. An electroacoustic device operable to generate an electrical signal representative of a music sound to be played, and a speaker assembly according to any one of claims 21 to 33 designed to be driven by the electrical signal. .   An auxiliary device comprising: a distributed mode speaker means; and a circuit for amplifying a signal derived from the high impedance input means comprising a high impedance input means and an amplifier and driving the distributed mode speaker means. An auxiliary device adapted to be connected to a sound reproduction system comprising an amplifier and a piston-type speaker for carrying out the process according to claim 1.   40. The apparatus of claim 38, wherein the circuit includes at least one volume control.   The circuit comprises first and second distributed mode loudspeaker means, and the circuit comprises a stereo acoustic amplifier and at least first and second piston type loudspeakers for performing the process of claim 1. 40. Apparatus according to claim 38 or 39, comprising first and second channels for enabling connection of the auxiliary device to a stereophonic sound reproduction system.   21. A process for modifying an existing sound reproduction system comprising a signal source, an amplifier and at least one piston type loudspeaker means, wherein the system operates in the process according to any one of claims 1 to 20. A process comprising connecting a distributed mode loudspeaker means to the system to adapt.   21. A process for modifying a digital piano with piston-type loudspeaker means for adapting the digital piano to the operation of the process according to any one of claims 1 to 20. A process comprising connecting a distributed mode loudspeaker means.   21. A process for modifying an electrical device comprising piston-type speaker means, wherein the acoustic device is adapted to adapt the electroacoustic device to the operation of the process according to any one of claims 1 to 20. A process comprising connecting a distributed mode speaker means.   34. At least one signal source, at least one speaker assembly according to any one of claims 21 to 33, and means for amplifying a signal from the signal source and driving the speaker assembly with the amplified signal A self-contained sound playback device.   An amplifier for amplifying a signal indicative of sound with left channel means and right channel means, the channel means for driving a first channel and piston type speaker for driving a distributed mode speaker An amplifier comprising a second channel.   Left and right inputs for connection to left and right outputs of a stereo acoustic signal generating device, and first and second buffer amplifiers for buffering applied signals connected to the left and right inputs, respectively And each of the buffer amplifiers has its output connected to a pair of additional amplifiers, the amplifier pair comprising a left distributed mode speaker and a left piston type speaker. Providing first and second left channel output signals for driving and first and second right channel output signals for driving right channel distributed mode speakers and right channel piston type speakers, respectively. An electrical circuit that is operable to.   The circuit of claim 46 including means for adjusting the relative level of the output signal provided by each pair of amplifiers.   Auxiliary device for connecting to a digital piano, input for receiving signals indicating activation of the keyboard and pedals from the digital piano, and selecting a signal from the library according to a digital library of piano sounds and input signals An acoustic signal generating means comprising means for performing, an amplifier for amplifying a signal derived by selection from the library, and a distributed mode adapted to be driven by the signal generated by the amplifier An auxiliary device comprising speaker means.   A process that emphasizes the spatial breadth of sound generated by at least one loudspeaker driven by a signal representing the sound to be reproduced within the listening space defined by the boundary, in order to generate a synthesized sound field Driving at least one other speaker with the signal, wherein the value of at least one parameter is different from the value in the sound field generated solely by the at least one speaker, and the difference between the values is spatially vast A process that includes a driving process to enhance sex.   50. The process of claim 49, wherein the parameter is a lateral initial energy ratio and the difference is an increment of its value.   50. The process of claim 49, wherein the parameter is an interaural cross-correlation coefficient and the difference is an increment of its value.   A process that emphasizes the spatial breadth of sound generated by at least one loudspeaker driven by a signal representing the sound to be reproduced within the listening space defined by the boundary, in order to generate a synthesized sound field Driving at least one other loudspeaker with said signal, wherein the value of the lateral initial energy ratio is such that the value of at least one parameter is compared with its value in the sound field generated solely by said at least one loudspeaker A process including a driving process in which the value of the intercorrelation coefficient between auditory and auditory increases is decreased. In a digital piano having a keyboard, a pedal, and a control signal generator for generating a control signal representing the activation in response to activation of the keyboard and pedal,
In response to the control signal, a first each modeling a sound, each representing the activation, and each representing a sound produced by a different first and second piano, respectively. And a driving signal generator for generating a second driving signal;
At least one first speaker designed to be driven by the first driving signal and operable to propagate sound by generating a first type of air disturbance pattern; ,
Designed to be driven by the second driving signal simultaneously with the first speaker and at least operable to propagate sound by generating a second type of air disturbance pattern One second speaker;
Improved to have.   54. The improvement of claim 53, wherein the at least one first speaker is a distributed mode speaker and the at least one second speaker comprises a pistonically movable element for propagating sound.   54. The improvement of claim 53, wherein the at least one first speaker is a distributed mode speaker and the at least one second speaker is a cone speaker. In a digital piano having a keyboard, a pedal, and a signal generator that generates a control signal representing the activation in response to activation of the keyboard and pedal,
A first library with digital samples representing sound from a first model of a grand piano;
A first drive circuit representing the activation in response to the control signal and generating a first drive signal derived from the digital sample of the first library;
A second library with digital samples representing sounds from a second model of the grand piano;
A second drive circuit that is responsive to the control signal to generate the second drive signal that represents the activation and is derived from the digital sample of the second library; A second driving circuit for simultaneously generating the first and second driving signals, respectively,
At least one distributed mode speaker designed to be driven by the first drive signal;
At least one cone speaker designed to be driven by the second drive signal;
Improved to have. In a digital piano having a keyboard, a pedal, and a signal generator that generates a control signal representing the activation in response to activation of the keyboard and pedal,
A library with digital samples representing the sound from the grand piano;
A drive circuit representing the activation in response to the control signal and generating a drive signal derived from the digital sample of the library;
At least one distributed mode speaker designed to be driven by the drive signal;
At least one cone speaker designed to be driven by the driving signal simultaneously with the at least one distributed mode speaker;
Improved to have. In a digital piano having a keyboard, a pedal, and a signal generator that generates a control signal representing the activation in response to activation of the keyboard and pedal,
A library with digital samples representing the sound from the grand piano;
Responsive to the control signal, a first drive signal representing the activation and derived from the digital sample is generated and a second drive signal representing the activation and derived from the digital sample A drive circuit for generating a signal, wherein the second drive signal is a drive circuit in which at least one parameter is modified with respect to the first drive signal;
At least one distributed mode speaker designed to be driven by one of the driving signals;
At least one cone speaker designed to be driven by the other of the driving signals simultaneously with the driving of the at least one distributed mode speaker;
Improved to have. A keyboard, a pedal, a signal generator for generating a control signal representative of the activation in response to activation of the keyboard and pedal, and at least one library comprising digital samples representing sound from at least one grand piano; A digital piano having a drive circuit that represents the activation in response to the control signal and generates a drive signal derived from the digital sample of the at least one library;
At least one first speaker designed to be driven by the driving signal and operable to propagate sound by generating a first type of air disturbance pattern;
At least one first designed to be driven by the driving signal at the same time as the first speaker and operable to propagate sound by generating a second type of air disturbance pattern. Two speakers,
Improved to have. A keyboard with keys corresponding to the notes;
A signal generator connected to the keyboard and generating a corresponding drive signal in response to activation of the keyboard;
A first sound generating unit connected to the signal generator and generating a sound corresponding to a musical note in response to a driving signal of the signal generator, the panel generating unit responding to a panel speaker and an acoustic signal; A first sound generating unit comprising at least one transducer for inducing resonant vibration in the panel speaker;
A second sound generation unit connected to the signal generator and generating a sound corresponding to a note in response to a driving signal of the signal generator simultaneously with the first sound generation unit, A second sound generating unit comprising two cone speakers;
Electronic equipment comprising.   The first and second sound generating units are operable to receive the same driving signal from the signal generator, and the first and second sound generating units are responsive to receiving the driving signal. The electronic device according to claim 60, wherein a sound is generated.   The first sound generation unit is operable to generate sound over a first range of sound frequencies, and the second sound generation unit is configured to generate sound over a second range of sound frequencies. 61. The electronic device of claim 60, wherein the electronic device is operable and a substantial portion of the first and second frequency ranges overlap.   The signal generator is responsive to activation of the keyboard for a first drive signal indicating a sound generated by the first piano in response to a corresponding activation of the keyboard of the first piano; and A second driving signal is generated by the second piano in response to a corresponding activation of the keyboard of the second piano, and the first sound generating unit is configured to generate the first driving signal. The response according to claim 62, wherein the second sound generation unit is responsive to generate a sound corresponding to the second driving signal. Electronics.   The signal generator is connected to one of the first sound generation unit and the second sound generation unit via a signal modifier, and the signal modifier is a driving signal generated by the signal generator. Of the first sound generating unit and the second sound generating unit, wherein the at least one of the first sound generating unit and the second sound generating unit 61. The electronic device of claim 60, wherein one responds to generate a sound corresponding to a note in response to the modified signal.   61. The electronic device of claim 60, wherein the first sound generation unit comprises one or more distributed mode speakers. The second sound generating unit is
A plurality of cone speakers each operable to output sound within a defined frequency range;
A crossover unit operable to receive a drive signal from the signal generator and to send a drive signal within a defined frequency range to a selected one of the plurality of cone speakers;
The electronic apparatus according to claim 60, comprising:   61. The electronic device of claim 60, wherein each of the first and second sound generation units includes an equalizer operable to equalize the output of sound having different frequencies by the sound generation unit. A method of simulating the sound of a keyboard instrument,
Providing a keyboard with keys corresponding to the notes;
Providing a signal generator for generating a corresponding driving signal in response to activation of the keyboard;
Activating the keyboard to generate a corresponding drive signal;
A first sound generating unit including a planar sound board using the generated driving signal and a transducer responsive to the acoustic signal so as to induce resonance vibration in the sound board; and a cone speaker Simultaneously starting a second sound generating unit comprising:
Including methods.   69. The method of claim 68, wherein the same drive signal is utilized to activate both the first sound generation unit and the second sound generation unit to generate sound.   The first and second sound generation units are activated to generate sound having first and second sound frequency ranges, with a substantial portion of the first and second frequency ranges overlapping. 70. The method of claim 69.   The generation of the drive signal is a first and second drive signal indicative of the sound of the first and second pianos in response to a corresponding activation of the piano key to the provided keyboard. The first driving signal is used by the first sound generating unit and the second driving signal is used by the second sound generating unit to output sound. 70. The method of claim 69.   The use of the generated driving signal is performed by correcting at least one of timing, reverberation and volume of the generated driving signal, and using the corrected signal, the first and second sound generating units. 69. The method of claim 68, comprising activating one of the two and activating the other of the sound generating units utilizing the unmodified signal.   69. The method of claim 68, wherein the first sound generation unit comprises one or more NXT speakers.   The second sound generation unit includes a plurality of cone speakers and a crossover unit for selectively applying driving signals having different frequencies to a selected speaker among the plurality of speakers. The method activates the plurality of speakers using selection of the acoustic signals at different frequencies while simultaneously at least one of the at least one signal by a signal having a frequency corresponding to that used to activate the plurality of speakers. 69. The method of claim 68, comprising activating a transducer.   Used to activate the first and second sound generation units so that the frequency response of the first and second sound generation units is substantially constant over the frequency range output by the sound generation unit. The method of claim 74, further comprising equalizing the acoustic signal.

Images