KR20100063142A - Apparatus and method for producing sound - Google Patents

Abstract

PURPOSE: An apparatus and a method for generating a sound generation are provided to improve a presence of a played sound by improving a speaker driven by a decoded signal. CONSTITUTION: A plurality of input devices(2) includes apparatuses like a CD player, a stereo FM tuner and/or a stereo tape player to play a stereo sound. A stereo amplifier unit(4) includes a general prior-amplifier, a control circuit and a power amplifier. A pair of speaker units(6) is respectively connected to right and left channel outputs of the amplifier. Each of speaker units includes existing corn type speaker and a dispersion mode speaker. The two of speaker units have same structure. Each speaker unit includes a prior frequency range two-way corn type speaker system including a base/a midrange speaker and a tweeter.

Description

Apparatus and method for sound production {APPARATUS AND METHOD FOR PRODUCING SOUND}

The present invention relates to an apparatus and method for sound production, and includes a novel speaker assembly and a novel electronic circuit for driving the speaker assembly. The invention can be applied in particular to the reproduction of recording sounds and broadcasting sounds, and to the production of sound from electronic musical equipment, in particular digital pianos.

For decades, the electrical generation and reproduction of sound has been the subject of constant research and development. One aspect of the study is to produce a perspective that improves the fidelity and quality of the sound produced by a speaker, such as a speaker, in which the moving elements of the speaker are faithfully dependent on changes in the electrical signals driving them. It relates to the performance of the speaker in terms of. Another aspect of research and development relates to techniques for encoding, decoding, broadcasting and decoding electrical signals representing sound in terms of improving the realism of sound reproduced by a speaker driven by the decoded signal.

As a result of research for improving speakers, there are many different types of speakers currently available that operate on different principles.

For example, there are conventional cone-shaped speakers in which a compliantly mounted cone of relatively rigid material is electromagnetically driven by a movable coil or movable magnet. This type of speaker has the widest popularity and is used in a variety of different applications, each with its own unique design requirements. Examples of applications include electrical or electronic musical instruments such as music, speech or audio-video elements, public address systems, computer audio outputs, movie and theater sound systems, in-car entertainment, public address systems, and digital pianos. There is a home entertainment system for playing.

No cone-shaped speakers are designed to produce sound with good fidelity over the audio frequency, especially the full range from below 50 Hz to about 20 kHz. Thus, for example, high quality sound for faithful music reproduction can only be made with a cone speaker when two or more units each designated for a particular frequency band are used in combination. Thus, the drive signal to these units is passed through circuits known as crossover circuits that deliver different frequency bands of this drive signal to the appropriate cone-shaped speakers. Many high quality speaker systems typically use at least three cone shaped speakers, i.e., high frequency speakers known as tweeters, mid-range speakers, and speakers for low frequencies known as woofers or sub-woofers. Modern cone speaker systems are capable of reproducing sound with a relatively flat frequency response that substantially exceeds the entire audible frequency range of people with relatively high fidelity, and are now the most extensive type of speakers for music reproduction. .

Another type of speaker used is an electrostatic speaker that causes a light tensioned plastic membrane to vibrate by an alternating electrostatic field generated from the drive signal by a pair of electrodes, the plastic membrane being positioned between the pair of electrodes. do. Since the membrane is particularly light and thus has little mechanical inertia, the movement of the membrane can reproduce the applied signal with relatively high fidelity even at high frequencies. A unique feature of electrostatic speakers is the high degree of clarity of the sound they produce compared to other types of speakers. However, currently commercially available electrostatic speakers are unable to produce the lowest frequencies generated by music. Despite the above facts and the fact that electrostatic speakers produce lower sound pressure levels than can be produced by cone-shaped speakers, many people find that electrostatic speakers are particularly capable of exceeding the frequency range in which they can operate. We think that we offer fidelity.

The cone-shaped speaker and the electrostatic speaker described above generate sound by the piston movement of the cone or the membrane.

A third type of speaker that does not rely on piston motion has been used in recent years. This is known as a distributed mode speaker. This has been explained in numerous publications. E.g:

(a) PCT application WO 97/09842

(b) US Patent 6,399,870

(c) The article "NXT Up Against the Wall", published by Henry Azima, published in the publication "Audio" published in September 1998 by Hechette Filipacchi Magazines Inc.

(d) A paper published by Neil Harris and Malcolm Omar Hawksford at the 103rd Audio Engineering Society Convention (26-29 September 1997, New York) as a Distributed Mode Loudspeaker (DML) as a Broad-Band Acoustic Radiator ".

(e) "Boundary Interaction of Diffuse Field Distributed Mode Radiators" presented by Henry Ajima and Neil Harris at the 103rd Audio Engineering Society Convention (26-29 September 1997, New York).

(f) Joe W. at the 104rd Audio Engineering Society Convention (Amsterdam, 16-19 May 1998). "Distributed Mode Loudspeaker Simulation Model" by Joerg W. Panzer and Neil Harris.

(g) "Distributed Mode Loudspeaker Radiation Simulation" presented by Joer Panzer and Neil Harris at the 104rd Audio Engineering Society Convention (San Francisco, CA, September 26-29, 1998).

The contents of these publications are incorporated herein by reference. The structure and operation of such distributed mode speakers have been described in numerous other published articles, some of which are referred to above as articles and articles.

As described in the publications, a distributed mode speaker generates a resonant bending wave in the panel and when the panel is attached to the panel and activated by an electrical audio signal, the resonant bending waves are generated on the panel surface. Disperse in the above complex pattern or in the required part of the panel surface. The magnetic pole of the panel causing the transducer to enter into this distributed resonance mode requires that the panel be configured to be able to be stimulated to enter this resonance mode, and the characteristics of the panel such that the required resonance mode is produced in the panel. Considering this requires the transducer to be carefully positioned. One of ordinary skill in the art of distributed mode speakers can design such speakers in a variety of sizes using a variety of different materials and different shapes.

Successful designs of distributed mode loudspeakers allow panel vibration and frequency response to vary in panel width, height, thickness, material, density of the material, poison ratio, bending strength, damping factor, shear ratio, shear It is a complex task because it depends on a very large number of different parameters, including modulus, the nature and location of the transducers, and the number of transducers used. Indeed, it is necessary to calculate the frequency response from the equation, in which reference is made to such publications regarding distributed mode speakers. Computer programs for performing these calculations and thus for the successful design of distributed mode speakers include: Huntingdon postcode PE29 6FW, Hinchingbrook Business Park, Kingfisher Way, Commercially available from Sign House, New Transducers Limited. This computer program allows the designer to input or select various suitable parameters of the proposed speaker, which calculates the resulting frequency response and vibration characteristics of the proposed speaker to allow the designer to make an appropriate design decision.

Apart from the computer program, the distributed mode speaker is a number of different sources, such as Cambridgeshire PE29 7DX Huntingdon Glebe Road Cyrus House Amina Tegnologys Limited, UK. Amina Technologies Ltd .; Scotland Coatbridge ML5 4TF Tannoy Limited; British Cambridgeshire PE29 6EY Stonehill Mission (UK) Limited; Or US PA 17603 Lancaster 2500 Colombia Avenue Armstrong World Industries;

Various proposals have been made for distributing distributed mode speakers along with other types of speakers. For example, since currently available distributed mode speakers cannot faithfully reproduce frequencies below about 100 Hz, it has been proposed to use speakers with sub-woofers separated from the distributed mode speakers, and both speakers have the appropriate filtering (crossover). Driven through circuits. In addition, the speaker assembly may be used in a general case such that distributed mode speakers are exclusively induced by frequency in bands appropriate for tweeters and cone-shaped speakers, or cone-shaped speakers are exclusively induced by frequency in bands appropriate for woofer and mid-range speakers. And commercially available in combination with one or more conventional cone-shaped speakers operating as distributed mode speakers used as tweeters, woofers and / or mid-range speakers, and conventional crossover circuits.

Another proposal for a full frequency range speaker system using distributed mode speakers is described in US Pat. No. 6,351,542 (Azima et al.). In this patent, distributed mode speakers form one wall of a closed chamber connected through a pipe to an enclosure containing a low frequency speaker (woofer) such that air pressure vibrations generated in the enclosure containing the woofer are The pipe is delivered to the closed chamfer. A distributed mode speaker is supported at the edge of the woofer by a compliant material and can move in a piston fashion in response to air pressure vibrations in a closed chamber, thereby vibrating in a substantially piston fashion along the woofer to produce low frequency sound. Can be generated.

The PCT application publication WO 97/09842 already mentioned above discloses a number of potential applications and configurations for distributed mode speakers. One configuration disclosed in this PCT application proposes the use of curved panels of distributed mode speakers in terms of focusing sound in a particular direction. Another configuration (65 in the drawing of the PCT application) is capable of resonant mode vibration, but occurs within the speaker enclosure when conventional cone-shaped speakers including woofers, mid-ranges and tweeters are driven without being vibrated through the electromagnetic transducer. It is proposed to form at least one wall of a case of a conventional speaker as a passive panel which allows vibration by resonance vibration induced by air pressure vibration. The configuration is said to allow for the desired coloration to be achieved.

An important advantage of distributed mode speakers is that they can be made in a relatively flat profile, thus allowing distributed mode speakers to be used when the cone-shaped speaker becomes uncomfortable or visually uncomfortable. However, distributed mode speakers are not yet widely used in the field of high fidelity music reproduction, which is probably well designed even if distributed mode speakers produce sound over a wide range of human hearing. It's probably not as flat as can be achieved with cone-shaped speakers.

Research to improve the realism of playback sound has led to the development of a stereo system, where recording or broadcasting is a separate signal provided on separate channels for driving a speaker located in front of the listener to its left and right sides. Include them. This system became widely used commercially and continuously in the 1950s and 1960s. These systems allow the listener to create the effect of the sound produced at different locations in front of the sound moving in front of it and across the sound "stage". These systems, for example, use a single signal channel to reproduce the sound, thereby providing the effect of the overall sound and sense of space produced by a musical instrument such as a piano or a symphony orchestra better than before.

In the 1960s, a four-channel system, known as a quadraphonic system, was developed in terms of further enhancing the effect of the sense of space and providing the possibility of special effects such as the apparent movement of sound sources through the three-dimensional space where the listener is located. Developed. Although some recordings and some broadcasting were made at the time, quadraphonic systems were not widely used. One of the problems with the system was that the systems required a special recording and broadcasting technique in which different signals were encoded in different channels, and four speakers were substantially in the center region of the space between the four speakers. It is located in the 4th corner of the listening room with the listeners located in. Although these systems were not widely used at the time, the effect of spatiality, that is, the effect that a listener hears sound in a space substantially larger than the space in which he actually listens, and the "environment", that is, the listener is surrounded by sound This could be improved over the stereo system in terms of producing the listener's feeling. Together, this effect provides the listener with a psycho-acoustic experience that is very similar to the experience of listening to music in a concert hall intended to provide sound reflections and adequate reverberation time by an appropriate level of walls.

In recent years, so-called "surround sound" systems have begun to be used, especially in cinemas and in so-called "home cinema" entertainment systems. One of the main purposes of the surround sound system is to produce special sound effects, such as the simulation of sound that a vehicle passes through a space containing a surround sound system and a listener. In general, a surround sound system includes five channels, each channel for driving left and right speakers in front of the listener, left and right speakers in front of the listener, and front center speaker. The system requires that the signal to be reproduced must be separately encoded on each of five different channels, which, when encoded into a recording or broadcast signal, each separate speaker driven separately by its own dedicated signal. To make it possible. In proper signal encoding, the surround system can improve the spatial and envelopment of the sound as compared to the stereo system.

Despite the extensive improvements made over the last few decades in speaker design and signal encoding as described above, there is a need for systems that can produce improved sound from electrical signals at low cost and, in particular, systems with improved spatial sense of sound.

In one aspect, the present invention improves the sense of space and / or presence by simultaneously driving at least one piston speaker and at least one distributed mode speaker, wherein the frequency range in which the speakers operate is at least partially audible frequency range by human Overlaps with The overlapping frequency ranges preferably include at least relatively low frequencies.

It has surprisingly been found that even in single channel (mono) systems, the sense of space and / or presence can be improved by reproducing sound in this manner. Accordingly, the present invention also applies to single channel, stereo, and multichannel sound reproduction systems.

The spatial sense of sound, and also the improvement of the sense of presence and thrill, will be discussed further with reference to the comparative experiments that have been performed, the results of which are shown in FIGS. 1 to 7 of the accompanying drawings. Practical embodiments of the present invention will be described with reference to FIGS. 8 to 31 of the accompanying drawings.

According to the present invention, an improved sound can be generated from an electrical signal at a low cost, and as a result, a system with improved spatial feeling of the sound can be made.

1 is a bar chart showing the Lateral Early Energy Fraction (LEF) measured in the first experiment using a stereo sound reproduction system, the LEF obtained using only conventional cone-shaped speakers, and the dispersion mode. LEF obtained using only a speaker and LEF obtained using both of the above according to the embodiment of the present invention are compared.
FIG. 2 is a bar chart showing the Inter-Aural Cross-Correlation Coefficient (IACC) measured in the experiments mentioned in connection with FIG. 1.
3 and 4 show bar charts similar to those of FIGS. 1 and 2, but show the LEFs and IACCs obtained in a second experiment in which a single sound reproduction system is used.
5 and 6 show the frequency response of the conventional cone-shaped speaker and the distributed mode speaker used in the third experiment relating to the present invention, respectively.
FIG. 7 shows the frequency response obtained when the speakers related to FIGS. 5 and 6 are driven simultaneously, and each of the different curves of FIG. 7 shows the results obtained when the relative sound pressure levels of the two speakers change.
8 is a block diagram of a stereo sound reproduction apparatus according to a first embodiment of the present invention.
9 is a schematic perspective view of a speaker assembly included in the apparatus of FIG. 8.
FIG. 10 is a schematic cross-sectional view of a portion of a distributed mode speaker included in the assembly of FIG. 9, illustrating an electromagnetic actuator attached to the speaker panel. FIG.
FIG. 11 is a schematic perspective view of a portion of the assembly of the distributed mode speaker of FIG. 9, illustrating the installation of a speaker panel in a support structure. FIG.
12 is a schematic side cross-sectional view of the speaker assembly of FIG. 9, illustrating a schematic block circuit for the assembly.
13 is a block diagram of a stereo sound reproduction apparatus according to a second embodiment of the present invention.
14 is an electrical block diagram of a signal conditioning circuit included in FIG. 13 for driving a distributed mode speaker included in the apparatus of FIG.
Since FIG. 15 is an electrical block diagram showing a modification of the circuit of FIG. 14, FIG. 15 constitutes a partial electrical block diagram of the third embodiment of the present invention.
16 is a block diagram of a stereo sound reproduction apparatus according to a fourth embodiment of the present invention.
17 is a block diagram of a stereo sound reproduction apparatus according to a fifth embodiment of the present invention.
18 is a block diagram of a stereo sound reproduction apparatus according to a sixth embodiment of the present invention.
19 is an electrical block diagram of a stereo amplifier included in the apparatus of FIG.
20 is a block diagram of a stereo sound reproduction system according to a seventh embodiment of the present invention.
21 is a block diagram of a stereo sound reproduction system according to an eighth embodiment of the present invention.
22 is a schematic perspective view of a stereo sound reproduction apparatus according to a ninth embodiment of the present invention.
FIG. 23 is a schematic circuit diagram of a portion of the device shown in FIG. 22.
24 is a block diagram of a stereo sound reproduction apparatus according to a tenth embodiment of the present invention.
25 is a block diagram of a "surround sound" sound reproduction system according to an eleventh embodiment of the present invention.
26 is a perspective view of a digital grand piano according to an embodiment of the present invention.
FIG. 27 is a schematic block diagram of the digital piano of FIG. 26.
Figure 28 is a rear perspective view of a digital upright piano in accordance with the present invention.
FIG. 29 is a block diagram of the digital piano shown in FIG. 28.
30 is a block diagram of a further embodiment of a digital piano according to the present invention.
31 is a block diagram of an add-on unit according to a further embodiment of the present invention, connected with the conventional digital piano to implement the present invention in combination with the add-on unit and the conventional digital piano. have.

In order to study the surprising increase in the effect of space achieved with the combination of dispersion mode and piston speaker according to the invention, a number of experiments have been carried out with different environments and uses, different environments, different speakers, and other equipment. Was performed.

All of the experiments included the use of the highest quality studio monitor cone speaker system and the highest quality distributed mode speaker. Each experiment included subjective listening tests performed on professional listeners, and others were presented in different experiments.

One experiment (the first experiment to be described in detail below) used a stereo system located in a specialized listening room designed to emulate the acoustically common listening conditions that can be experienced in a home living room. The listening room was roughly the same size as a large living room with randomly distributed reflective and non-reflective walls and carpets on the floor and some items of high absorbent furniture. The sound was relatively "dead" in the living room, including soft furniture and curtains.

The second experiment was performed using mono equipment in another professional listening room, which was half the size of the listening room used in the first experiment described above and had walls absorbing frequencies above 10,000 Hz. Similar to the first listening room, the sound was relatively “faint”. Mono equipment was used.

Mono equipment was also used in the third experiment to be described. The speakers are in particularly unfavorable acoustic state, in particular located at the intersection of two corridors each having a width of 2 m and orthogonal to each other. Listening tests were performed in one of the hallways about 3 meters away from the speakers with the speakers placed there.

In all experiments, the subjective listening tests showed a perceived improvement in the sense of space when the cone-shaped speakers were driven alone or when the distributed mode and cone-shaped speakers were driven simultaneously compared to when the distributed mode speakers were driven alone. It was. In order to determine whether the perceived increase in space is simply subjective, or whether the perceived increase has a scientific basis, Late Early Energy Fraction (LEF) and Inter Aural Cross Correlation Coefficient (IAC) Auditory cross correlation coefficient) was measured according to conventional measurement techniques in the first and second experiments. The nature of these LEFs and IACCs is fully explained below.

The subjective quality of the sound produced by the different equipment used in the experiment was also taken into account in the listening test. In the first experiment (stereo), the sound pressure level of the dispersion mode and the cone-shaped speaker was set substantially to the same value in the microphone to measure, and the experiment indicated that the quality of the sound from the combined speakers was It was subjectively considered to be better than the quality of the sound produced by the single cone speaker or the single distributed mode speaker.

In a second experiment, the sound pressure level of the distributed mode speaker was set to 4.2 decibels lower than the sound pressure level produced by the cone speaker (measured at the microphone). This number was chosen after trying a number of different relative sound pressure levels. The quality of the sound produced by the combined speakers was also considered to be better than the quality produced by the cone-shaped speaker alone or the distributed mode speaker alone.

In a third experiment, the effect of varying the relative sound pressure levels of the distributed mode and cone-shaped speakers on the subjective quality of the sound was tested, and the distributed mode speakers were lowered from 5 decibels to +/- 3 decibels than the cone-shaped speaker. It was found that driving provided the optimal cognitive quality, and the quality was found to be better than the perceived quality when listening to the discrete mode speaker or the cone-shaped speaker alone.

The third experiment also included measurements to determine the frequency response of the two speakers alone and the frequency response of the combined speakers. The frequency response of the combined speakers was determined for a number of different relative levels at which the speakers are driven. From these experiments and calculations, the frequency response curves of the combined speakers were obtained which were smoother than the frequency response of the distributed mode speaker alone.

Each of the three experiments will now be described in more detail.

Details of the 1st experiment (stereo)

The first experiment was performed under the following conditions and by the following equipment.

(a) The room was generally a dry room with additional absorbent panels located randomly on the side and back walls. The room size was 0.87 m long x 4.6 m wide x 2.79 m high = 88.17 cubic meters.

(b) Speakers and microphones were located at the vertices of equilateral triangles. The distance between the speakers and the microphone was 2 meters (each side of the triangle = 2 meters). The speakers were positioned away from the wall of the room.

(c) The speakers consisted of two conventional cone-shaped speakers and two distributed mode speakers.

(d) The conventional cone-shaped speakers were Genelec Model 1029A 40W monitors with integrated amplifiers. Technical data: Bass5 "drive unit; Treble triple 3/4 'metal dome drive unit; crossover frequency 3.3kHz; frequency response 70-18,000Hz.

(e) The distributed mode speakers, manufactured by Amina Technologies Limited (described above), consisted of a 610 mm x 492 mm aluminum core, a polyester skin, and four exciters (10 w / exciter). Each was a 40w open back panel. The frequency response was 20 KHz at 80 Hz.

(f) For LEF measurements, the CALREC Soundfield microphone model ST250 was used. B + K Head and Torso Simulater (HATS) microphone model 4100 was used for IACC measurements.

(g) For this measurement, a maximum length sequence signal was used, an impulse response was extracted, and spatial measurements were performed on the impulse response. The software used was the Cool Edit Pro P.C version of Aurora Plugins.

(h) The distributed mode speaker and the cone speaker were driven to provide a pressure level substantially equal to the sound pressure level in the microphone.

A listener located in a listening space, such as a concert hall, receives both sound energy directly from the source (eg, orchestra) and after being reflected at the boundaries of the listening space. The total energy ratio was received for the listeners received after the direct sound reception was known from the lateral initial energy ratio (LEF) and reflected from the boundaries of the listening space within a period of approximately 50 milliseconds. High frequencies are absorbed better than low frequencies, and also generally contain less energy than low frequencies, with most of the reflected energy in the low frequency range. LEF is generally measured in multiple frequency bands, especially in the following bands.

88 to 176 Hz (known as 125 octave band)

176 to 353 Hz (known as 250 octave band)

353 to 707 Hz (known as 500 octave band)

707 to 1414 Hz (known as 1,000 octave band)

Within the limits, it is widely believed that the higher the LEF in the concert hall environment, the greater the effect of the sense of space in this frequency band. Since the object of the present invention is to create an improved effect of the sense of space, the measurement of the LEF of the combined sound field produced by simultaneously driving the distributed mode speaker and the cone-shaped speaker was performed, wherein the distributed mode and the cone-shaped speaker were individually When compared with the measurement of LEF.

1 is a bar chart showing the results. As can be seen in the figure, vertically patterned bars 500a, 500b, 500c, and 500d individually represent the LEF for the cone-shaped speaker alone in each of the octave bands defined above. Lifeline bar bars 502a through 502d represent the LEF for the distributed mode speakers alone in the same octave band. Ladder bars 504a through 504d represent the LEF for the combination of the dispersion mode and cone speaker according to the present invention.

As can be seen in FIG. 1, the LEF for the sound field produced by the combined distributed mode and cone-shaped speaker according to the invention has respective octave bands than the LEF in the sound field generated from the cone-shaped speaker alone. Is significantly higher. Accordingly, FIG. 1 shows that the subjective perceived significant increase in the effect of the space achieved by the combination speakers according to the invention compared to the cone-shaped speakers is consistent with the LEF increase in the octave band, these frequencies It is also consistent with the widely held view that the increase of the LEF in the band provides an increased effect of the sense of space in a concert hall environment. In other words, the sound field generated by the combined speakers according to the present invention is different from the sound field generated by the cone-shaped speaker alone, i. This is in the sense of an increase in the value of). It is believed that the increase in sense of space perceived by the subjective listening test mentioned above results from the creation of a physically different sound field when the combination according to the invention is used compared to a single cone speaker.

Also, in the 125 to 250 octave frequency band, one can observe that the magnitude of the difference in LEF between the combined speakers and the cone-shaped speakers is substantially greater than the difference in LEF in the 500 to 1,000 octave frequency band. This feature is associated with increased warmth in the sound. In other words, in the case where the difference magnitude of LEF in each of the four octave frequency bands shown in FIG. 1 is the same, this may indicate an increase in the sense of space, but not an increase in the intensity of the sound.

Also noted from FIG. 1, the LEFs of the discrete mode speakers alone are larger than the LEFs of the cone-shaped speakers alone in all four frequency bands. In the 125 to 250 octave frequency band, the LEFs of the distributed mode speakers alone are smaller than the LEFs of the combined speakers. In the 500 to 1,000 octave band, the LEFs of the single distributed mode speakers and the LEFs of the combined speakers are of similar size, and the difference seen in this octave band is hardly noticeable. These results indicate that the increase in the sense of space exhibited by using the combined speakers in accordance with the present invention compared to the distributed mode speaker as confirmed in the subjective listening test is not as great as compared to the cone-shaped speaker alone, and the dispersion It is suggested that the mode speakers provide a greater sense of space than the cone speaker. However, an important point of the present invention is to achieve a substantial increase in the sense of space beyond that obtained by a single cone speaker while maintaining fidelity. Recall that distributed mode speakers are not yet widely used in applications that require the highest fidelity levels.

Inter Aural Cross Correlation Coefficient (IACC) represents a measure of the degree of correlation between the sound pressure signals received at the listener's ear. The IACC is consequently measured conventionally using a dummy head, which has each hole at the location of the human aural passage, and each hole has a small microphone. In one or more of the 1,000, 2,000 and 4,000 octave frequency bands, the lower values of this correlation coefficient represent an increased sense of space, the values of which are as follows.

1,000 band: 707-1414 Hz (as already indicated above)

2,000 bands: 1,414-2,825 Hz

4,000 bands: 2,825 to 5,650 Hz

2 is a bar graph showing the results of the IACC measurement performed in the first experiment. In Fig. 2, the vertical bar bars 506a through 506d, the horizontal bar bars 508a through 508d, and the bar bar bars 510a through 510d are single cone-shaped speakers, single distributed mode speakers, and Each of the two combinations of IACCs according to the invention is represented in each of four octave bands, ie the four octave bands are described above with reference to the 500 octave band (described above with reference to the LIF) and the 1,000, 2,000 and 4,000 octave bands. to be. As can be readily seen from the figure, the value of IACC for combined speakers according to the present invention is significantly smaller than that of a sole cone speaker in the 1,000, 2,000 and 4,000 octave bands. As mentioned above, the smaller the value of this coefficient in this frequency band, the greater the effect of the sense of space, and as in the above LEF value, this represents an increase in the sense of space in sound.

Although FIG. 2 includes IACC measurements in the 500 octave band, as will be appreciated the wavelengths of sound energy in this frequency band are practical because the high correlation factor can be expected from the energy received at the listener's two ears. It is inappropriate.

Thus, it can be seen that both the LEF and IACC measurements on the stereo equipment used in the first experiment agree with the subjective effects of the sense of space observed in the listening test.

Details of the second experiment (mono)

The second experiment was performed under the following conditions and with the following equipments.

(a) The room was acoustically treated to absorb sound above 10,000 Hz to an average of 0.3 sec. The room size was 5.6 m long x 3.2 m wide x 2.4 m high = 48.28 cubic meters.

(b) In this measurement the microphone was placed 1.5 m away from the speakers on axis. The front of the distributed mode speaker is aligned approximately perpendicular to the back of the case of a conventional cone speaker.

(c) The cone speaker was Tannoy Near Field Dual-Concentirc Monitor model 6NFM Mark II having a frequency response of 44 Hz to 20 KHz. The advantage of this unit is that HF and LF are at the same axis point for the measurements. The distributed mode speaker panel used was manufactured by Amina Technology Limited and includes a skin with a 500 x 700 mm PVC dipped paper honeycomb core and four exciters (10 w / exciter). It is a 40w open back panel with a frequency response of 80Hz to 20KHz.

(d) AKG C34 Variable Polar Microphone was used for LEF measurements. Neuman Binaural Head was used for the IACC measurement.

(e) Impulse response and spatial data were also extracted from the maximum length signal. The software used is MLSSA P. C. software.

(f) Using an individual amplifier, the DML panel was set to 4.2 dB lower than the Tannoy.

3 and 4 are bar graphs showing the LEFs and IACCs measured in the second experiment. The bar pattern is the same as in FIGS. 1 and 2. Thus, the bars 512a through 512d in FIG. 3, and the bars 518a through 518d in FIG. 4, individually represent LEFs and IACCs for sole cone speakers; The bars 514a through 514d in FIG. 3, and the bars 520a through 520d in FIG. 4, represent LEFs and IACCs for a single distributed mode speaker, and the bars in FIGS. 3 and 4 ( 516a through 516d and 522a through 522d represent LEFs and IACCs for the combined digital mode and cone shaped speaker according to the present invention. As in FIGS. 1 and 2, each bar in FIGS. 3 and 4 represents an appropriate value at a particular octave frequency as shown in the figure.

The test of FIG. 3 shows that the LEF values for the combined speaker according to the present invention are higher than the LEFs for the single conventional cone-shaped speaker and the single distributed mode speaker in each octave frequency band. This is consistent with the perceived increase in the sense of space observed in the subjective test, as described above. The fact that the magnitude of the difference between the bars 516a and 512b is greater than the magnitude of the difference between the bars 516c and 512c represents a significant improvement in the sound excellence.

4 shows that the IACCs of the speakers combined according to the invention in the 1,000 and 4,000 octave bands are significantly lower than the IACCs of the sole cone speakers. This is consistent with the observed increase in spatiality, but in the 22,000 octave band, the 518c and 522c IACC values are nearly identical. As described with reference to FIG. 2, the IACC in the 500 octave band shown in FIG. 4 is not appropriate.

3 and 4 coincide with the surprising and record increase in the perceived effect of the sense of space in the subjective tests conducted with the mono system used in the second experiment.

Details of the third experiment (mono)

This experiment was carried out in an environment and equipment different from that of the first and second experiments described above. The experiment consisted of subjective tests using a single channel (mono) with speakers of adverse hearing (already described above), and frequency response measurements performed in an echo-free chamber. Measurements of LEF and IACC were not performed in this experiment.

The conventional cone speaker used through this experiment is a JBL LSR32 passive studio monitor comprising three drive-units covering a frequency band of approximately 30 Hz to 20 KHz. DML is manufactured by Amina Technology Limited. The DML panel included a synthetic dipped paper honeycomb core with a synthetic resin saturated fiber optic skin, measured 60 cm x 60 cm. Excitation of four electromagnets was present and the frequency response was 80 Hz to 20 KHz.

The DML panel is placed on top of a conventional speaker and attached with strong double-sided adhesive tape. Pink noise was used as the test signal for all measurements to ensure proper signal-to-noise ratio at all frequencies of interest (pink noise is a wideband random signal containing the same signal energy per octave of bandwidth). The output signal from the signal generator was connected to the input of the two-channel power amplifier through a pair of universal filter sets to enable customization of the frequency range of the signal provided to each speaker. The relative output levels of the two speakers are adjusted using a switchable attenuator that matches the drive for the amplifier that provides power to the speaker.

On-axis frequency response

Figure 5 shows the magnitude of the constant frequency response of the conventional cone-shaped speaker, Figure 6 shows the frequency response for the DML panel. The low-frequency response of the DML panel was cut off below 100 Hz according to the manufacturer's recommendations. An in-line attenuator was tuned to provide approximately the same constant level from the two speakers in the frequency range from 500 Hz to 5 KHz.

The frequency response shown in FIGS. 5 and 6 was calculated on a computer in both cases with and without taking into account phase. The comparison between the resulting frequency response and the measurement of the frequency response obtained when the speakers were combined clearly showed the phase increase and furthermore the interference that occurred between the two speakers. Surprisingly, the response can be accurately determined by summing the individually measured responses with respect to phase, the frequency response of the combined output of the two speakers. This is the case where the response of the arbitrary, relative combination of output levels can be determined. FIG. 7 shows that the frequency response of the combination can be determined by summing on a computer at a level of DML that varies by 3 dB from -12 dB to +12 dB compared to a conventional speaker.

Subjective evaluation

Subjective tests were performed using the same equipment as used in the measurements, but on two speakers in a semi-reflective space (blocking corridors as described above) instead of the chamber without echo.

All listening was done in single-channel mono using various commercial music records played from CD. First, a marked change in the sense of space was noticed as the DML panel was switched in and out. The test subjects agreed that the addition of the panel improved the feeling of space compared to the conventional cone type speaker alone. Second, the relative level of the two speakers was changed until the optimum for the perceived improvement by the subjects was equal to the level. This was done using a "balance" control on the amplifier to maintain a constant overall level. The subjects agreed on the optimal level setting of the -5 dB output from the DML panel compared to the level used in the measurements (the same level from 500 Hz to 5 KHz). The test subjects agreed on this value within ± 3 dB.

 Additional tests involve setting a relative level of threshold beyond which no change in sound is detected as one speaker switches in and out, while the other speaker remains constant. The levels were quickly determined to be about -35 dB detection threshold for DML panels and -20 dB detection threshold for the conventional speakers.

Argument

Frequency response measurements clearly showed that the DML panel had a less smooth frequency response than the conventional cone speaker. This is not surprising at all when other radiation mechanisms are considered. The DML panel also suffers from a pronounced dip as a response at around 7 kHz. But what is surprising is the degree to which the DML panel and conventional speakers are interfering. DML panels emit sound in a way that the panels do, because the field of vibration substantially extends beyond the surface of the panel. Thus, one can reasonably expect that there will be no particular phase associated with the emitted sound field at all; The result of these measurements is at least one point in space and beyond the narrow frequency band (but for all audio frequencies), the panel being measurable, repeating, causing constructive interference to the sound emission from another speaker. It shows that we have a possible phase response.

Figure 7 shows the frequency response of the output combined with two speakers when the level of the DML panel is changed in contrast to the level of a conventional cone speaker. As can be expected, the low level of DML output has little effect on the response of conventional cone-shaped speakers, and the high relative level shows the response dominated by the influence of the panel. However, the most interesting thing to note in the figure is the relative level at which the response that would otherwise be gentle for conventional cone-shaped speakers is overturned by interference from the output of the DML. The figure shows that for relative levels above -3 dB, the response is adversely affected by the panel in this experiment, but for low levels this is not the cause. This is in accordance with the subjective observation that the relative level of -5db is for the optimum for the desired sound quality; For higher relative levels of DML outputs, trade-offs are possible for frequency responses that do not increase in the sense of space.

Summary of Experiment Results

As in the first and second experiments, the subjective tests showed a marked increase in the effect of the sense of space, which was present in mono systems with speakers in adverse hearing. The frequency response measurements and calculations have shown that the speakers combined in accordance with the present invention can achieve significantly better frequency response compared to a single distributed mode speaker with an appropriate level of drive signal.

Practical Example

As can be appreciated from the above discussion of experiments conducted with subjective experiments and scientific measurements, the present invention provides a practical and simple solution to the problem of increasing the spatial sense of the sound produced by the speakers, in particular With the addition of distributed mode speakers and eliminating the need for additional signal channels or complex signal encodings, high quality wideband frequency range piston speakers can be used without losing the high fidelity of the sound, increasing the spacing of the generated sound. Can be.

In practicing the invention, the distributed mode and the speakers of the piston must operate on a common part of the audible frequency band. Preferably all of the speakers are operating in virtually the entire audible frequency band, for example a piston speaker can operate from 20 Hz to 20 KHz and the distributed mode speaker can operate from about 100 Hz to 20 KHz, or the distributed mode When the speaker's technology is further developed, the speakers mode will be able to operate at full audible frequency, 20Hz to 20KHz. Within the scope of the invention narrowband frequencies are used depending on circumstances such as cost and planned use. For example, the distributed mode speaker may have one or more octaves in a much narrower band frequency, such as from 100 to 1,000 Hz, or from 200 to 2,000, or from 4,000 Hz or 6,000 Hz, as indicated above. It may be limited to a frequency band covering the. As a further specific example, the frequency band of the distributed mode speaker or speaker may be from 100 to 6,000 Hz, and the frequency band of the piston speaker may be from 800 to 8,000 KHz.

In a further alternative, when the distributed mode and piston speakers operate in a common part of the frequency range, the tweeter may be at the highest frequencies since the highest frequency of the piston speaker may actually be lower than the highest frequency of the distributed mode speaker. It can be configured by a distributed mode speaker.

Thus, in general, the frequency range of distributed mode speakers may be wider or narrower than that of piston speakers; The lower the limit of the frequency range of the distributed mode speaker, the lower or higher than the limit of the frequency range of the piston speaker; The upper limit of the frequency range of the distributed mode speaker may be lower or higher than the limit of the piston speaker. The best frequency range for the piston and distributed mode speakers can be determined by experimentation depending on the application, cost and other applications or other market specific requirements.

Many practical embodiments of the invention will be described below. In most of these embodiments no specific frequencies will be provided. These should be selected from the ranges exemplified in the above discussion depending on the circumstances of the particular product designed according to the description of the embodiment.

In addition, the sound reproduction devices of the following embodiments in the use or location of the speakers will not be described. The user or installer may be able to determine the best location in any particular listening room. If the distributed mode speaker is a unit that is physically separate from the piston speaker, the two speakers may be located close to each other, ie on top of each other or in a different position, for example intended for the listener. Distributed mode speakers may be located behind or to the side of the area. After the encoding is performed under the assumption that the position of the speakers in the surround sound system is important and that the speakers will be located at a predefined position, this constraint on the connection, even if according to the encoding of the signal in other channels, affects the invention. Does not give.

In addition, tests (not mentioned in the above description of the experiment) can be used with the introduction of a delay between the output of the piston and the distributed mode speakers, and in particular the signals applied to the distributed mode speakers are applied to the piston speakers. It should be understood that it has been shown that it may be delayed relative to the applied signals. If a delay is applied, it should generally never exceed 80 msec, and preferably not exceed 35 msec. The introduction of such delays has been known in informal testing to enhance the "imaging" or "localisation" of sound in stereo applications or surround sound applications. Such improvements in imaging and localization improve the clarity of the music as it is listened to.

These improvements are not caused by transients from the piston speakers in sound as a result of the delay but by transients from the distributed mode speakers, rather than transients from the piston speakers. It is thought to occur because it is covered by the phenomenon.

It should be understood that although the foregoing effects are provided regarding the foregoing description of the LEF and IACC and the description of the following delay theory, the present application is not limited to these descriptions. The explanations given are based on current knowledge and measurement techniques in the audio field, but the psychoacoustic effects in humans of sound that are susceptible to humans are a very complex subject and difficult to provide accurate explanations (or impossible in some situations). Well known.

Many practical embodiments of the invention will now be described.

First embodiment

8 to 12 show a stereo sound reproduction system according to a first embodiment of the present invention.

As shown in FIG. 8, the system includes a plurality of input devices 2, such as a CD player, a stereo FM tuner and / or a stereo tape player, to reproduce stereo sound such as music; It includes a stereo amplifier unit 4 in a conventional configuration, and a pair of speaker units 6 connected to the left and right channel outputs of the general pre-amplifier, control circuit and power amplifier, and the amplifier 4, respectively. Each of the speaker units 6 comprises a conventional cone speaker and a distributed mode speaker driven in accordance with the present invention. The two speaker units 6 are identical to each other.

As shown in FIG. 9, each speaker unit 6 includes a conventional full frequency range two-way cone speaker system including a base / midrange speaker 10 and a tweeter 12. It includes a case (8). Each of the cone-shaped speakers 10 and 12 includes a separate electromagnet drive unit, which may be a movable coil or movable magnetic tape for driving the individual cones. The case has front, rear, top, bottom, and side panels 8a, 8b, 8c, 8d, 8e, 8f. The front panel 8a has holes 14, 16 at the rear side where the cones of the speakers 14, 16 are located. The cones of the speakers 10, 12 fill the holes 14, 16, so that the cone shaped speakers produce sound in a free air state in a conventional manner, as in the prior art. ) Forms a closed chamber in which the cone-shaped speakers 10 and 12 are arranged. The interior of the closed chamber in the case 8 may comprise any conventional structures or damping material.

The distributed mode speaker 22 is firmly fixed in the vertical direction at the top of the case 8 and includes a speaker panel 24 and an electromagnet actuator 26 attached to the rear surface of the panel 24. The square frame 28 securely secured to the edge 30 along the case 8 is in approximately the same plane as the front face of the case 8 and the panel 24 is coupled to the actuator in a resonant dispersion mode acoustic vibration. The panel 24 is supported in such a way that it is stimulated in a well known manner.

The panel 24 and frame 28 form a front wall of a housing 32 located on the top and sides of the case 8, and the rear and top walls 32a comprise a plurality of holes. It is composed entirely of a metal mesh so that sound generated from the back surface of the panel 24 can be transmitted substantially freely through the mesh wall 34 to the free air.

The exciter 26 is a non-magnetic, light weight rigid cylindrical former 34, wrapped and supported by the former 34, as shown entirely in the schematic cross section of FIG. 10. And a magnet 38. The magnet 38 is essentially cup-shaped and includes a wall 38a, a cylindrical sidewall 38b, and a solid cylindrical central core 38c at the circular end or bottom. When the coil 36 is energized by an alternating electrical signal, the resulting electromagnet force between the coil 36 and the magnet 38 causes relative vibrational movement between the former 34 and the magnet 38. Soft flexible material 39 is firmly fixed by adhesion between the outer surface of the central core 38c of the magnet 38 and the inner cylindrical surface of the former 34 so that the former Compared to the flexible support for the magnet. The magnet is not supported other than as described above as known in distributed mode speaker technology, but is substantially heavier than the former to allow vibration to be transmitted to the panel 24 as a result of the physical inertia of the magnet due to its weight. . As is known in the art of distributed mode speakers, additional support for the magnet 38 (no additional support is shown in FIG. 10 or not included in the present embodiment) may be possible, but this is not necessarily the vibration of the magnet. Enable operation.

As schematically shown in FIG. 10, the panel 24 has an internal honeycomb structure 24a having passages extending from the front to the back of the structure, where such passages are the front and back layers 24b and 24c. Are closed individually. The structure is chosen to be lightweight according to the design principle of the distributed mode speaker, and roughly designed for this purpose according to the design principle of the distributed mode speaker as already described above, and the excitation located on the panel 24. The activity of the instrument 26 can be set to resonant dispersion mode vibration in the form of a bending wave.

As already presented, in order to enable this vibration, the panel 24 is flexibly mounted to the frame 28. 11 shows an example of a mounting means that is applicable and flexible for this purpose, ie the edge area 24d of the panel 24 and the back side 28a of the frame 28 (shown as an L-shaped cross section). An example of a soft foam stripe 40 securely attached in between is shown. The stripes 40 are discontinuous, so that the edge region 24e of the panel 24 can vibrate freely without any attachment to the frame 24 in the region 24e. According to the design principle for distributed mode speakers, the regions 24d and 24e of the panel will be selected to optimize the properties of the panel which can be excited with resonance distributed mode vibration.

As schematically shown in FIG. 12, each speaker unit 6 is connected to the output of the conventional amplifier shown in FIG. 8 via suitable wires, and the cone-shaped speakers 10 and 12 and distributed mode speakers ( 22, a pair of input terminals 42 for providing drive signals. These signals are applied to the woofer and tweeter cone-shaped speakers 10 and 12 separately through the low frequency pass filter 44 and the high frequency pass filter 46, which together constitute a conventional crossover circuit, and high frequency pass protection. To the distributed mode speaker 22 via a filter and attenuation circuit 48. The cone-shaped speakers 10 and 12 and the filters 44 and 46 are designed such that the speakers 14 and 16 together can substantially reproduce the entire frequency range from 20 Hz to 20 KHz, And ready, a conventional cone speaker system can be created. The distributed mode speaker 22 with the high pass protection filter included in the circuit 48, at this stage of the technology, states that distributed mode speakers do not effectively reproduce sound having a frequency at least generally less than 100 Hz. Considering the fact, it is actually designed and prepared to reproduce many full frequency ranges. Thus, the circuit 48 is adapted to block signals with frequencies less than 100 Hz to enable the distributed mode speaker 22 to reproduce frequencies within 100 KHz to 20 KHz. An attenuator is included in the circuit 48 such that the distributed mode speaker 22 produces a sound pressure level that is less than the sound pressure level produced by the cone speakers 14 and 16. For example (as described above in the context of the experiments performed) a sound pressure level of -5db + or -db is the desired sound pressure level difference.

If the embodiment of Figs. 8 to 12 consists of components of appropriate quality, then a high-compliance music playback system may be combined with conventional speakers in which single conventional speakers, single distributed mode speakers, or distributed mode speakers are used as woofers. It provides an improved sense of space compared to the sense of space that can be achieved with a device used simply as a tweeter.

Preferably, the high pass protection filter attenuation circuit 48 is adjustable by the user, allowing the user to set different levels of attenuation depending on room acoustics following setup and trial and error. Further, preferably the circuit is adjustable to introduce a delay in the signals applied for the Busan mode speaker in the range of 0 to 35 msec.

In use, the speakers of the system described with reference to FIGS. 8 to 12 can be positioned in a conventional manner, but should ensure that the distributed mode speakers can emit in the rearward and omnidirectional directions as far as possible, ie the speakers are walled. Or directly from other items that prevent backward propagation of sound from distributed mode speakers.

Second embodiment

FIG. 13 shows an alternative embodiment of the present invention, comprising conventional input devices as described above, conventional stereo amplifiers, and a conventional pair of cone loudspeakers 50. A pair of auxiliary sound reproduction units 52 have been added to a conventional hi-fidelity music reproduction system, one of which is for the right channel and the other for the left channel. They are for retrofitting conventional high fidelity systems into systems according to the invention.

Each of the auxiliary units 52 includes a distributed mode loudspeaker 54 and a signal conditioning amplifier 56 having an input terminal 58 and an output terminal 60, The input terminal 58 is connected to the left and right speaker output terminals of the amplifier 4, respectively, and the output terminal 60 is connected to each of the distributed mode speakers 54. Each signal conditioning amplifier 56 is powered from the mains line indicated by reference numeral 62. For convenience, the input terminal 58 is connected to each of the terminals of the speaker unit 50 by a short wire, whereby the outputs of the amplifier 4 and the input of the auxiliary unit 52 are provided. Eliminate the extra long wires between them.

14 is a block diagram of each of the signal conditioning amplifiers 56. As shown, an attenuator 64 is connected to the input terminal 58 to supply a signal to a digitally controlled volume control circuit 66, the digital controlled volume control circuit ( The output of 66 is supplied to a power amplifier 70 via a 7 band equalizer 68, the output of which is connected to the terminal 60.

The attenuator 64 includes a high resistance value resistor 72 connected across the terminal 58 with a tab 74 to supply the low level signal described above to the digital volume control 66. The resistance value of the resistor 72 is such that the total impedance arising from the connection of both the signal conditioning amplifier 56 and the speaker 50 to the output terminal of the amplifier 4 is due to the speaker 50 alone. Selected to be substantially close to the impedance, the amplifier 4 is not adversely affected by connecting the amplifier to auxiliary units in addition to the conventional cone-shaped speaker 50.

The seven band equalizer includes a number of preset controls 68a to preset relative amplification to be applied to seven different frequency bands. The setting of control 68a is selected to compensate at least somewhat all deviations in the frequency response of the distributed mode speaker 54 and to remove all low frequencies below 100 Hz that the distributed mode speaker cannot reproduce sufficiently. .

The microcontroller 76 controls the digital volume control circuit 66, the equalizer 68, and the power amplifier 70. The microcontroller 76 is an infrared detector that responds to a manual volume control device 78 and a handheld remote control device (not shown) operated by a user of the system to adjust the volume. Controlled by the signal from the detector 80, the user of the system can adjust the volume of the sound produced by the distributed mode speaker to the volume produced by the cone speaker. To avoid wasting power, the device 56 may cause the device 56 to enter a power-down mode when no signal is supplied from the amplifier 4 to the device 56. It is composed. An input detection circuit 82 is connected to the tap 74 and provides a control signal to the microcontroller 76 in response to the detection of the signal appearing on the tap 74, the microcontroller 76 accordingly. The circuit is programmed to enter a power-up mode in which it operates.

In the embodiment of FIGS. 13 and 14, as described above with respect to the prior art embodiment, the conventional cone-shaped speaker 50 operates over the full frequency range and the distributed mode speaker 54 is practical. By operating a range and consequently by adding a pair of auxiliary units to the conventional high fidelity sound reproduction system described with reference to FIGS. 13 and 14, the conventional system implements the present invention and provides an improved sense of space. Can be converted to an improved system.

Thus, the auxiliary unit 52 is generally manufactured and sold separately from the high fidelity system and can be added to conventional high fidelity systems. The signal conditioning amplifier 56 may be physically mounted on or within the base or housing that supports the distributed mode speakers, or alternatively may be separated from it.

In addition, although FIG. 13 shows two separate signal conditioning amplifiers 56, it is alternatively possible to provide a two channel signal conditioning amplifier, each channel having an input attenuator 64, as described above, Digital volume control 66, equalizer 68, and power amplifier 70, with a single microcontroller controlling both channels. In such a configuration, the input detector is coupled to both input attenuators and is adapted to enter the power-up mode in response to a signal in one or both of the channels. Such a two-channel signal conditioning amplifier may comprise all elements in a single housing to be integrated into a housing or base supporting one of the distributed mode speakers, or alternatively may be configured as a separate item from the distributed mode speakers. have. Providing a single microcontroller will also save cost.

In order to simplify as much as possible the action of connecting the auxiliary unit 52 to a conventional sound reproduction system, each auxiliary unit 52 is provided with an additional output terminal (not shown), the output terminals being the input terminal. For direct connection to the field 58 and for connection to conventional cone-shaped speakers by short wires (not shown), the short wires can be included in the auxiliary unit when manufactured and sold. As mentioned above In a variant in which a two channel signal conditioning amplifier is provided, there may be two sets of additional output terminals, one for each channel.

Third Embodiment

FIG. 15 shows a modification at the input end of the circuit shown in FIG. 14, wherein the modification is such that the signal conditioning amplifier is not only at a high level (in the case of the configuration of FIG. 14) but also at a line level. It also accepts input at line level. For this purpose, the line level input terminal 82 is connected to one input of the input switch 84 and the other input of the input switch is connected to the output of the attenuator 64. The input detector circuit 80 is replaced by a detector circuit 86 with two inputs, one of the two inputs connected to the tap 74 and the other input to the line input 82. . The input detector circuit 86 is arranged to transmit a signal to the microcontroller 76 indicating when a signal is present at the line input 82 or at the tap 74, and the microcontroller sends the signal. Interpreted, it is arranged to properly set the input switch 84 and connect its output to the line input or to the tap 74. As described above with reference to FIG. 14, the microcontroller also causes the circuit to enter a power-up mode in response to a signal from the input detector 86.

In the embodiment of FIG. 14, the left and right channels may be provided in a single unit and may be controlled by a single microcontroller as described above.

Further, as described above, in order to simplify the action of connecting the auxiliary units to a conventional sound reproduction system, an additional output for connecting directly to the input terminal 58 and for connection to a conventional cone-shaped speaker 50. Terminals may be provided.

Fourth embodiment

Figure 16 illustrates an alternative form of auxiliary unit for converting a conventional high fidelity system into an embodiment of the present invention. In Fig. 16, the conventional high fidelity unit comprises an input device 2 and a conventional amplifier 4, and a pair of conventional cone-shaped speakers 50, in this embodiment, are added to the system. It is assumed to be more efficient compared to distributed mode speakers. 16 shows a left and right auxiliary unit 88 each comprising a distributed mode speaker 54 and an attenuator 92 connected to an input terminal 90, wherein the attenuator 92 is the conventional cone speaker. A connection is made between an input terminal 90 and an output terminal 94 for connection to 50.

The configuration shown in FIG. 16 assumes that when all speakers are connected, the resistance at the terminals 90 is within the impedance range that the amplifier 4 can handle.

Fifth Embodiment

FIG. 17 shows the same configuration as shown in FIG. 16 except for the assumption that the distributed mode speaker 54 is more efficient than the cone speaker 50. Thus, the attenuator circuit 92 is connected between the input terminal 90 and the distributed mode speaker 54, rather than between the input and output terminals 90, 94. As in the case of FIG. 16, also in FIG. 17, when all the speakers are connected, it is assumed that the total impedance at the terminals 90 is within an impedance range that the amplifier 4 can handle.

Sixth embodiment

In Fig. 18, the sound reproduction system includes conventional input devices 2 and a stereo amplifier 100 for achieving the purpose as described above, each of which has a distributed mode speaker ( 106 and first and second left channel stereo output terminals 102 and 104 connected to conventional cone shaped speaker 108 and first and second right connected to distributed mode speaker 114 and conventional cone shaped speaker 116, respectively. And channel stereo output terminals 110 and 112. The conventional cone shaped speakers 108 and 116 may both preferably be full frequency range speakers and, for example, the cone shaped speakers as bidirectional or three-way devices with conventional crossover circuitry. In combination, it can reproduce sounds in the range of 20Hz to 20kHz. In addition, as discussed above, the distributed mode speakers 106 and 114 include a practical full range, and preferably produce sound in the range of at least 100 Hz to 20 kHz.

As shown in FIG. 19, the amplifier 100 includes a conventional input selection circuit 118 to receive a user select input from the conventional devices 2, the conventional input selection circuit 118 Left and right output terminals 120 and 122 are provided, respectively. The left output terminal 120 is connected to the input terminals of both the left distributed mode speaker signal processing channel 124 and the left cone shaped speaker signal processing channel 126 whose outputs are connected to the terminals 102 and 104, respectively. The right output terminal 122 of the input selector 118 is an input terminal of both the right distributed mode speaker signal processing channel 128 and the right cone shaped speaker signal processing channel 130 whose outputs are connected to terminals 110 and 112, respectively. Connected to the field.

The channels 124, 126, 128, and 130 are controlled by a microcontroller 132 that receives control input from the volume control 140 relative to a conventional set of controls 136. The conventional control 136 is arranged to be operated by the system user and may include all conventional controls such as left-right balance control, treble and bass control, graphic equalizer control, and the like. The relative volume control 140 is also arranged to be operated by the user, and on the one hand the relative between the distributed mode speakers 106 and 114 and on the other hand between the conventional cone shaped speakers 108 and 116. To set the volume.

Each of the distributed mode speaker channels 124 is a seven-band equalizer with digital volume control, a preset, and power, similar to the elements 66, 68, 68a, and 70 described above with reference to FIG. It includes an amplifier. Each of the cone-shaped speaker channels 126 and 128 is a conventional filter, a volume control (in this case digitally controlled), a power amplifier, and a conventional cone-shaped speaker for driving a conventional equalizer such as a graphic equalizer. It may include circuit elements.

The conventional control 136 controls the four channels 124, 126, 128, and 130 according to the settings (volume, filtering, equalization, etc.) of the conventional control 136 to produce the required outputs. The relative control 140 adjusts the relative power levels of the signals supplied to the terminals 102 and 110 on the one hand and the terminals 104 and 112 on the other hand, so that distributed mode speakers 106 and 114 Volume or sound pressure level generated by a) can be relatively adjusted relative to the volume or sound pressure level produced by conventional cone-shaped speakers 108 and 116, and preferably, as described above, the distributed mode speaker Can be set to -5 decibels +/- 3 decibels compared to the output of the conventional cone-shaped speakers, and also other possible considerations of the user's preferences, room acoustics and the characteristics of the speakers used. You can also provide settings.

Thus, according to the present embodiment, a novel stereo amplifier is provided having first and second left channels and first and second right channels for simple connection to the aforementioned distributed mode and cone speakers. Is implemented.

Seventh embodiment

20 is a block diagram of another embodiment of the present invention that includes a self-contained sound playback device 142. The self-contained device 142 includes first and second left line level connection sockets 143 and 144 connected to an active distributed mode speaker 145 and an active conventional cone-shaped speaker 146 respectively, and First and second right line level connection sockets 147 and 148 connected to a distributed mode speaker 149 and an active conventional cone-shaped speaker 150, respectively. The word " active " related to the speakers described in the prior art and in the figures means that a built-in power amplifier is provided in the speaker, allowing the speaker to reproduce sound from line level signals.

Self-contained playback device 142 has one or more stereo signal sources 151 (eg, FM radio tuner and / or compact disc player) with left and right outputs supplied to left and right channels 152 and 153 respectively. It includes. Each of these channels includes a volume control 154 with an output terminal 155, which output terminal 155 has an input of relative volume control 156 and an input of a main power amplifier 157. And to an output socket (socket 144 in the left channel, socket 148 in the right channel). Left and right built-in conventional cone-shaped speakers 158 are included in the device 142 and are connected to the outputs of the power amplifier 157 through respective switches 159, respectively. Connectors 143, 144, 147, and 148 are preferably standard sockets that accept standard plugs. A mechanical connection is provided between the sockets 144 and 148 and the respective switches 159 so that the switches are open to disconnect the integrated speakers when plugs (not shown) are inserted into the sockets. (open)

The user operated main volume control device 160 simultaneously controls the main volume control circuits 154 of the two channels. User operated control elements such as knobs are provided to adjust the relative volume control circuit 156 to relatively adjust the output of the distributed mode speakers to the output of the cone shaped speaker. In this embodiment, it is assumed that each of the two relative volume control circuits has its own distinct user operated control elements, so that the relative volumes of the distributed mode and cone-shaped speakers in each of the left and right channels are separate. Can be adjusted. If desired, the circuit may be modified to provide a single relative volume control element operated by the user to simultaneously adjust the relative volumes of the left and right channels.

Preferably, the frequency range reproduced by the speakers 145, 146, 149, and 150 is as described above for the distributed mode and conventional cone-shaped speakers, and the relative volumes are described above in the various parts of this specification. Can be adjusted.

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

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

Eighth embodiment

The embodiment of FIG. 21 illustrates that the built-in speaker 158, the main amplifier 157, and the switches 159 (and the mechanical links to the sockets 144 and 148 associated therewith) are removed. Same as the embodiment of 20.

9th embodiment

22 and 23 illustrate an embodiment of the present invention, the left distributed mode and conventional cone type as described with reference to FIG. 18 driven by a conventional portable player 165 via an amplifier unit 164. Speaker and right distributed mode and conventional cone-shaped speakers 106, 108, 114, and 116, the conventional portable player 165 being, for example, a CD player or a tape player, with left and right channel level outputs 166 and 167).

The amplifier unit includes left and right channel buffer amplifiers 169 and 170, first and second left channel power amplifiers 171 and 172, and first and second right channel power amplifiers 173 and 174. One housing 168. Left and right channel input leads 175 and 176 are connected to line level outputs 166 and 167 by conventional plugs 177 and 178, respectively, to the left generated by the portable player 165. And right line level signals to the input of the buffer amplifiers 169 and 170, respectively. The left channel power amplifiers 171 and 172 are generated by the buffer amplifier 169 to drive the distributed mode speaker 106 and the conventional cone-shaped speaker 108 via terminals 179 and 180, respectively. Amplified signal independently. Similarly, the right channel power amplifiers 173 and 174 operate the buffer amplifiers to drive the right distributed mode speaker 114 and the right conventional cone-shaped speaker 116 through terminals 181 and 182, respectively. Amplify the signal supplied by 170).

The four power amplifiers 171, 172, 173, and 174 may each include volume control circuits to allow the output of the four speakers to be adjusted separately. In this embodiment the frequency range in which the distributed mode and conventional cone-shaped speakers operate is as described above, and the difference in sound pressure output between the distributed mode speakers and conventional cone-shaped speakers is also adjusted within the above-mentioned range. do.

Thus, the amplifier unit 164 adds two conventional cone-shaped speakers and two distributed mode speakers to the conventional stereo player, thereby enabling the present invention to be implemented using a conventional stereo player with line level output. . It cannot be sold with or without connecting leads.

In the modification, the individual plugs 177 and 178 shown in FIGS. 22 and 23 can be replaced by standard stereo plugs such as “mini-plugs”, which means that the player It is possible when provided with a conventional socket type that can accept.

10th embodiment

Fig. 24 shows another embodiment of the present invention in the form of a self-contained sound reproduction device. This embodiment includes a schematic representation of a housing 185 that includes all the elements necessary for the implementation of the present invention. Thus, the housing 185 includes left and right distributed mode speakers 186 and 187 and left and right bidirectional conventional cone shaped speaker systems 188 and 189, and the left and right bidirectional conventional cone shaped speaker systems 188. And 189 include tweeters 188a and 189a, woofers 188b and 189b, and conventional crossover circuits 188c and 189c, respectively. One or more stereo signal sources, together with the necessary control and speaker drive circuitry, are generally indicated by reference numeral 190 and also included in housing 185, and conventional user-operated controls such as volume, balance, treble and bass control. Is provided. The signal channels for driving and controlling the distributed mode speaker and the conventional cone-shaped speaker are as described above, so both the overall volume control and the relative volume control which relatively adjusts the volume level of the distributed mode and the volume level of the conventional speaker with each other. It includes.

As in the above embodiment, although the frequency range in the case of a self-contained portable device is smaller than, for example, a high-fidelity system for home use, the frequency range produced by the distributed mode speaker is a conventional cone type. It substantially overlaps or is preferably substantially the same as the frequency range produced by the speaker. Self-contained device 185 may 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 implemented in a computer, some or all of the control is implemented in software.

Eleventh embodiment

The present invention is used in so-called "surround sound" systems. 25 shows an example of such an implementation.

In Fig. 25, a conventional surround sound input device 191 is connected to a conventional surround sound amplifier 192 having five channels, i.e., the five front channels, i.e., the left front channel, the front center channel, the right front channel, As a left channel and a right channel, each of these is connected to different speakers 6 which will be located in the appropriate place in the listening room. Thus, the speakers 6 as described in detail with reference to FIGS. 9 to 13 embody the present invention in a surround system.

Embodiment of the present invention in a digital piano

It is well known that even the highest quality digital pianos available today produce sound that is relatively out of tune. Implementing the present invention in a digital piano allows the digital piano to provide even more substantial musical sound. In particular, the digital piano according to the present invention can produce a highly rich sound with a random component, and if the piano is configured with an appropriate quality, the random component is a high quality acoustic grand Gives the listener the impression of being close to the sound quality of an acoustic grand piano. This can be achieved at a significantly lower cost than the highest quality acoustic piano.

grand piano

Figure 26 illustrates a perspective view of a digital grand piano in accordance with an embodiment of the present invention. The piano includes a case 200 having a conventional hinged lid 202 supported by a leg 201 and opened by a conventional brace 203. A keyboard 204 of a type conventionally used in a digital piano and a pedal set 205 for performing a normal function are supported in a normal state by the case 200. Preferably, for the purpose of giving the player a feeling of a good concert grand, the piano comprises a conventional high quality grand piano function (not shown) connected to the keyboard (as already known in the digital piano art).

The case 200 supports two speaker assemblies 210 and 212, each assembly comprising a tweeter 216, a mid-range unit 214, and a sub-woofer. -woofer) 218, each arranged in correspondence with the high, mid-range, and bass portions of the keyboard. Each of the speakers 216, 214, and 218 is a conventional electro-magnetically driven cone-shaped speaker arrangement such that the cone is vertically upwards and the resulting sound is reflected by the lid of the piano. This direction is particularly preferred for tweeters and mid-range speakers, but the direction of the sub-woofer is not particularly important.

The case 200 also supports two distributed mode speakers 220 and 222, with the distributed mode speakers 220 and 222 positioned horizontally so that sound radiates up and down. As an example, the panels of the distributed mode speakers 220 and 222 are measured at 700 × 500, respectively.

It should be understood that the locations shown in FIG. 26 of conventional speaker groups adjacent to the keyboard and distributed mode speakers away from the keyboard are exemplary only. The conventional and distributed mode speakers may alternatively be interleaved with each other, or the position may be reversed relative to that shown in the figure. In addition, the tweeter, mid-range unit, and sub-woofer of a conventional speaker assembly may be separated and interleaved with the distributed mode speaker.

As shown in FIG. 27, the signal is 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) arranged under the keyboard 204 of the piano. The MIDI signal is sent to the first audio signal generator 230 and the second audio signal generator 231, both of which reproduce the sound of the grand piano. Arranged to respond to the MIDI signal and the foot pedal switch 107 to produce an audio signal. The first and second generators 230 and 231 may be implemented by a conventional computer including known software for this purpose.

In this embodiment, the first audio signal generator 230 includes a first high quality sample library 232 and a first sound module 234. The second audio signal generator 231 includes a second high quality sample library 237, a second sound module 238, and a physical modeling unit 239. Respective libraries 232 and 237 contain digital samples recorded from different high quality grand pianos, preferably concert grandes. Thus, for example, the first sound sample library 232 may include a 1.6Gb Steinway sample library and the second sample library 237 may include a Yamaha 30Mb sample sound library.

The sound modules 234 and 238 include software programs that select sound samples from the sound library 232 and 237 in response to receiving a MIDI signal and a signal from the foot pedal switches 107. Since the second sample library 237 is considerably smaller than the first sample library 232 (in this embodiment), the second audio signal generator 231 is capable of performing conventional sound samples selected by the second sound module 238. It also includes a physical modeling unit 239 arranged to modify in a manner.

The audio signal from the generator 230 is amplified by the amplifier 240, which amplifies the two distributed mode speakers 220 and 222.

The audio signal from the generator 231 is amplified by the amplifier 245 and supplied to the crossover unit 247 to drive two conventional speakers 210 and 212. The crossover unit 247 sends the high frequency, mid-range, and low frequency signals in a conventional manner to the tweeter 216, mid-range unit 214, and woofer 218 of the conventional speakers 210 and 212, respectively. Send to)

Cone-type speakers reproduce sound in virtually all audio frequency ranges, ranging from 20 Hz to 20 kHz or 45 Hz to 20 kHz. Distributed mode speakers produce a practical range of sound, ranging from 80 Hz to 20 kHz or 100 Hz to 20 kHz. The sound pressure level provided by the distributed mode speakers is adjusted to be smaller than that produced by conventional cone-shaped speakers, or as described above, or depending on the acoustic environment of the auditorium or room in which the piano is played, the output of the distributed mode speakers is conventional. It may have the same or higher sound pressure level than cone speakers. In order to allow the sound pressure level of the distributed mode speaker to change independently of the sound pressure level of the conventional cone-shaped speaker, separate volume control for the distributed mode and the cone-shaped speaker is preferably provided although not shown in the figure.

When the piano is played, distributed mode speakers and conventional speakers are driven simultaneously. As a result, different air disturbance patterns propagated by distributed mode speakers and conventional cone-shaped speakers, respectively, combine, resulting in complexity and richness resulting from randomly varying interactions between the different patterns. Atmospheric disturbance patterns may be generated to provide a substantially richer sound than that produced by each of the separate speaker types. This abundance is further enhanced when the signal used to drive distributed mode speakers is different from the signal used to drive conventional speakers.

In addition, as described with reference to the above-described embodiment, the sense of space is improved by the combination of the dispersion mode and the conventional cone-shaped speakers.

Although samples from two different grand piano models are used in this embodiment, further abundance can be achieved by using samples from three or more different grand pianos, in which case Different speakers are each driven by signals derived from different sample sets. In addition, samples other than Steinway and Yamaha samples can be used, and sound libraries preferably used for instruments both include the maximum number of samples available for the current state of the art. More specifically, as the capacity of the computer memory increases and the cost decreases, it is possible to provide sound libraries containing more and more samples, thus enabling better sound quality.

Digital Upright Piano

In FIG. 28, an upright digital piano that produces a lower quality sound than that produced by the pianos of FIGS. 26 and 27 includes a case 251, which has a pair of distributed mode speakers. 253 and a backplate 252 that also supports a pair of conventional cone-shaped speakers 254. In this embodiment, in contrast to the previous embodiment, only two cone-shaped speakers are provided to save cost. The distributed mode speakers 253 are provided in a direction parallel to the plane of the back plate 252 of the case 251. The cone shape of the two conventional speakers 254 has a cone-shaped axis perpendicular to the plane of the back plate 252.

FIG. 29 is a schematic block diagram of the piano of FIG. 28. In contrast to the previous embodiment, a single audio signal generator 230 including a sound library 262 and a sound generation module 260 is provided to save costs. The generator 230 generates an audio signal by using the sound library 262 based on the reception of signals from the infrared pickup 207 and the foot pedal switches 206.

As in the previous embodiment, distributed mode speakers 253 and conventional cone-shaped speakers 254 are arranged to be driven simultaneously through amplifiers 245 and 247 so that the electronic piano is conventionally coupled with distributed mode speakers 253. To produce an atmospheric disturbance pattern that is a combination of the sound outputs by the speaker 254, and thus more closely mimics the propagation of sound generated by the acoustic instrument as described above. In addition, as is apparent from Fig. 29, even though no crossover circuit is included because the two cone-shaped speakers 254 are assumed to be identical and thus have a relatively limited frequency range, The frequency range of distributed mode speakers should overlap with the frequency range of conventional cone-shaped speakers as long as it can enhance the spatial sense of sound. However, although the quality of the sound produced by the embodiment of FIGS. 28 and 29 may not be as good as the sound produced by the embodiment of FIGS. 26 and 27, using elements of suitable quality, FIGS. 28 and 29. Even with the 29 embodiment, overall better quality can be achieved than the currently available piano.

For the purpose of providing some further refinement, a modification of the circuit of FIG. 29 is shown in FIG. 30. Here, the audio signals generated by the generators 230 and 260 are sent to a signal modification unit 265, such as a digital signal processing unit, where the signal modification unit 265 is a cone speaker 254. Produces a modified signal that is sent to an amplifier 247 driving. The signal modification unit 265 is arranged to change the timing and the sound quality of the audio signal output by the sound generating unit 260. This signal modification unit 265 includes a conventional user interface (not shown) that allows a user to select how the output by the sound generation unit 260 is modified. Since the quality of the signal driving the cone-shaped speaker is slightly different from the signal quality driving the distributed mode speaker, the richness of the sound can be somewhat improved in this way. If desired, another signal modification unit can be placed between the sound generation module 260 and the amplifier 245, which drives distributed mode speakers to provide more abundance.

In the above three embodiments, although the sound is described as output through pairs of distributed mode speakers and conventional pairs of speakers, simultaneously outputting sound corresponding to the same note through a single distributed mode speaker and a single cone speaker It is natural that similar random mixing of atmospheric disturbance patterns can be achieved thereby.

In the above embodiments, although the infrared motion detection system for detecting the operation of keys has been described using infrared motion detection, other means can be used to detect the depression key, for example, electromechanical. Motion detection systems can be used to detect position, pressure, and key motion speed.

Auxiliary unit for digital piano

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

As shown in FIG. 31, the auxiliary unit 302 includes a distributed mode speaker 304 driven by an amplifier 306, which amplifier 306 outputs a MIDI signal conventionally provided for a currently available digital piano. A signal is received from the audio signal generator 230 (as described above) connected to the 314 via a cable 310 and a plug 312.

The conventional digital piano 300 is a three-way conventional cone speaker system comprising a woofer 318, a mid-range unit 320, and a tweeter 322 driven through a conventional crossover circuit (not shown). 316 to operate to produce a full audio frequency range of substantially 20 Hz to 20 kHz. The distributed mode speaker 304 operates to produce a frequency of a practical portion of the frequency range produced by the speaker system 316, such as in the range of 100 Hz to 20 kHz.

Although not shown in FIG. 31, a conventional digital piano 300 generally operates using a sound library of samples recorded from a quality concert grand. For the reasons described with respect to the embodiment of FIGS. 26 and 27, the audio signal generator 230 also preferably includes a sound library containing samples recorded from high quality concert grandes of different models.

The auxiliary unit 302 can be manufactured and sold separately from the digital piano and connected to an existing digital piano owned by the purchaser. By simply connecting the auxiliary unit 302 to the existing MIDI output of the digital piano and setting the volume control of the digital piano to one level, in addition to the sound produced from the distributed mode speaker 304, the conventional speaker system 316 By allowing sound to be produced, the advantages of the present invention can be achieved.

Variations and modifications

As can be seen from the foregoing, the present invention can be implemented in a wide variety of ways. Numerous further modifications of the above-described variations may be made within the scope of the present invention.

For example, the invention can be implemented in public address systems, sound systems in theaters and cinemas, in-car entertainment systems, or monitoring systems in recording or broadcast studios.

In addition to the digital piano, the present invention can be implemented to reproduce sound from other electric or electronic musical instruments such as an electric guitar.

Although conventional cone-shaped speakers have been used in each of the embodiments described above, in certain situations, alternatives such as electrostatic or piezoelectric speakers are provided with a flat panel or membrane equipped for vibrational operation and driven by a piezo electric transducer. It is possible to use in place of a piston speaker of the type. However, in most environments electromagnetically driven cone shaped speakers will be preferred.

Although the stereo device has been described in all the sound reproducing device embodiments of Figs. 8 to 24, all of the above embodiments can be modified to a single channel, single device. As already explained, the effects of the invention can also be achieved in a single application.

The delay in the signal applied to the distributed mode speaker relative to the signal applied to the piston speaker has been described above. This will be provided in all embodiments other than those described with reference to the drawings. Preferably, when there is a delay, it will be adjusted by the user to suit the environment in which the present invention is deployed.

In addition, further similar processing may be provided for signals applied to distributed mode and / or piston speakers, for example to provide reverberation, equalization, or other effects.

Various preferred frequency ranges and relative output levels have been provided in the description of numerous above embodiments. It is to be understood that these are only examples and that many changes are possible. However, it is important that the frequency range of the distributed mode speaker or speakers overlap with the frequency range of the piston speaker or speakers. In addition, in many cases, especially in the case of a sound reproduction system implementing the present invention, optimal results can be achieved by arranging the sound pressure levels of the distributed mode speakers slightly smaller than those of cone-shaped speakers (eg, only a few decibels difference). However, improvements can be made to produce significantly lower sound pressure levels than cone-shaped speakers provided with distributed mode speakers, and of course, the pressure level of distributed mode speakers may be so low that the sound produced by the distributed mode speakers cannot be perceived. Can not be done. In experiments, a distributed mode speaker sound pressure level, which is as low as -35 decibels compared to cone speakers, can still be perceived, but this level is a limitation of the improvement.

In certain circumstances, it may be desirable for the sound pressure level produced by the distributed all speakers to be greater than that produced by the piston speakers.

186,187: Distributed Mode Speakers 188a, 189a: Tweeter
188b, 189b: woofer

Claims (1)

As a method of producing stereo sound,
(a) using a left channel speaker device and a right channel speaker device each having distributed mode speaker means and piston speaker means,
(b) the sound from each speaker device is received after being reflected directly from the speaker device in the listening space having the boundary and from a sound reflecting surface forming at least a portion of the boundary,
(c) the respective loudspeaker arrangements such that each means produces sound with a frequency response having an operating range when measured under an anechoic condition and a roll-off range greater and less than the upper and lower operating ranges respectively. Wherein said distributed mode speaker means and said piston speaker means overlap over an overlap range comprising a plurality of octaves, at least one of which is in a frequency range consisting of a band of 1 kHz to 4 kHz,
(d) the distributed mode speaker means and the piston speaker means of the left channel speaker device are driven simultaneously from the common left audio signal such that all of them produce a sound represented by a common left channel audio signal at least over the overlap range; ;
(e) the distributed mode speaker means and the piston speaker means of the right channel speaker device are driven simultaneously from the common right audio signal such that they all produce a sound represented by a common right channel audio signal at least over the overlap range; ;
(f) 2 meters in front of each speaker device, the sound pressure level generated from said distributed mode speaker means is not greater than the sound pressure level produced by said piston speaker means.

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