WO2007127757A2 - Procédé et système de conformation de faisceaux sonores surround exploitant la partie de chevauchement des plages de fréquences des circuits d'attaque - Google Patents

Procédé et système de conformation de faisceaux sonores surround exploitant la partie de chevauchement des plages de fréquences des circuits d'attaque Download PDF

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Publication number
WO2007127757A2
WO2007127757A2 PCT/US2007/067342 US2007067342W WO2007127757A2 WO 2007127757 A2 WO2007127757 A2 WO 2007127757A2 US 2007067342 W US2007067342 W US 2007067342W WO 2007127757 A2 WO2007127757 A2 WO 2007127757A2
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WIPO (PCT)
Prior art keywords
channel information
signal
surround
frequency
speaker
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PCT/US2007/067342
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English (en)
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WO2007127757A3 (fr
Inventor
John L. Melanson
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Cirrus Logic, Inc.
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Publication date
Priority claimed from US11/380,840 external-priority patent/US7606380B2/en
Application filed by Cirrus Logic, Inc. filed Critical Cirrus Logic, Inc.
Publication of WO2007127757A2 publication Critical patent/WO2007127757A2/fr
Publication of WO2007127757A3 publication Critical patent/WO2007127757A3/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S3/00—Systems employing more than two channels, e.g. quadraphonic
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2205/00—Details of stereophonic arrangements covered by H04R5/00 but not provided for in any of its subgroups
    • H04R2205/022—Plurality of transducers corresponding to a plurality of sound channels in each earpiece of headphones or in a single enclosure
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2430/00—Signal processing covered by H04R, not provided for in its groups
    • H04R2430/20—Processing of the output signals of the acoustic transducers of an array for obtaining a desired directivity characteristic
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2499/00—Aspects covered by H04R or H04S not otherwise provided for in their subgroups
    • H04R2499/10—General applications
    • H04R2499/15—Transducers incorporated in visual displaying devices, e.g. televisions, computer displays, laptops
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R5/00—Stereophonic arrangements
    • H04R5/02—Spatial or constructional arrangements of loudspeakers

Definitions

  • the present invention relates generally to home entertainment devices, and more specifically, to techniques for sound beam-forming using the overlapping portion of driver frequency ranges in a speaker driver set.
  • Audio systems in home entertainment systems have evolved along with theatre audio systems to include multi-speaker surround sound capabilities. Only recently have discrete surround signals been available from sources in home entertainment systems and further only recently have encoded sources reached a sufficient level of home use for consumers to justify installation of the requisite equipment. With the development of Digital Versatile Disc (DVD) technology that provides surround audio source information for movies or surround-encoded music, and sophisticated computer games that provide surround audio, surround speaker installation in home environments has become more desirable and frequent. With the recent availability of digital television (DTV) signals, which can include surround audio signals as part of their audio-visual (A/V) information, increasing sales of televisions and/or DTV sets including surround channel outputs are expected.
  • the surround signals may be encoded in a pair of stereo signals, such as early DBX or as in more recent Dolby or THX surround encoding, or may constitute a fully separate audio channel for each speaker, often referred to as discrete encoding.
  • an amplifier unit which may be included in an AV receiver or in a television, provides signals to multiple sets of speakers, commonly in what is referred to as a 5.1, 6.1 or 7.1 arrangement.
  • the 5.1 arrangement includes right, center and left main speakers located in the front of the room, and a right-left pair of surround speakers located in the rear of the room for providing an aural environment in which sounds can be psycho-acoustically located such that they emanate from any horizontal direction.
  • the " .1" suffix indicates that an additional subwoofer is provided for providing low frequency sounds that are typically not sensed as emanating from a particular direction.
  • the 6.1 configuration adds a center channel speaker in the surround speaker set and in a 7.1 configuration, an additional pair of speakers is included over the 5.1 configuration and located even farther back in the room from the surround channel speakers.
  • surround channel speakers can be costly and undesirable in many home environments. Wiring must be added, and locations with unobstructed paths to the listening area must be available. Since the surround channel audio sources are generated for a particular location of the speakers, they cannot be simply placed at any location in the room and still function properly. It is desirable to position the surround speakers in such a way that the surround sound is diffuse, often limiting possible locations for speaker placement.
  • the term "diffuse" indicates that the sound does not appear to emanate from a single direction, which is generally provided via reflections from one or more surfaces that cause the sound to be reflected toward the user from multiple angles.
  • surround channel signals are provided to speakers placed behind the listener.
  • surround channel signal is provided to speakers placed in front of the listener.
  • Simulated surround sound implementations typically use filtering and/or delays to alter mono or stereo audio signals to provide outputs for additional front speakers to generate the surround field.
  • U.S. Patent 6,937,737 describes a simulated surround sound system that provides the right and left surround channel information to each side (right and left) of an additional stereo speaker pair as well as to each side of the main stereo speaker pair. The frequency response of the system is controlled to cause the apparent position of the surround channel information to appear wider than the speaker position.
  • Such systems do not provide surround sound performance approaching that of actual surround sound implementations.
  • Most full-range speaker systems used in high fidelity stereo and main channel installations include multiple drivers, such as two-way (woofer/tweeter) or three-way (woofer/midrange/tweeter ) speakers.
  • each driver is typically assigned to a specific frequency band by a crossover network that filters the input audio signal to provide the proper signals for each driver.
  • Such a network is also generally necessary to protect the high-frequency driver (tweeter) from damage due to low frequency content.
  • multi-driver speakers are not usually employed in the above-described array systems, and instead, a uniform set of drivers is employed in the same frequency range in order to provide beam-forming in the particular range of the set of drivers .
  • the above stated objective of providing a beam- forming speaker system without requiring an array with a large number of elements and with no additional drivers is satisfied in a method and system.
  • the method is a method of operation of the system or a device incorporating the elements of the system.
  • the system uses a set of at least two drivers having substantially differing frequency ranges, such as a pair of drivers used in a stereo two-way speaker.
  • the overlapping portion of the frequency ranges of the drivers is used in substantially opposing polarity response with respect to a surround channel input, in order to generate one or more beams directed away from a listening position, so that the surround channel is heard substantially only as reflections.
  • the beam may be directed above the listener, or to the right or left, depending on the orientation of the drivers with respect to each other.
  • the response to main channel information is provided to the drivers in an ordinary manner, with a phase-alignment of matching polarity, thus providing a wide beam directed at the listening position for the main channel information.
  • An electronic network receives the main and surround channel information and combines them to produce the signals provided to the drivers.
  • the network may be a passive network for power-splitting, or an active circuit driving power stages, and may be included within a speaker cabinet .
  • the network may be provided as part of a device such as a receiver or television that has separate outputs for each driver in external driver pairs.
  • the drivers may be included within a device such as a television or portable stereo, along with the electronic network, providing a compact surround beam-forming solution.
  • Each side of a stereo speaker set may be provided with such a set of beam- forming drivers so that two main and two surround beams are provided by the system. Additional speakers or sets of beam-forming speakers can be added to the system to increase the quality of the sound reproduction.
  • Figure 1 is a pictorial diagram of a system in accordance with an embodiment of the present invention.
  • Figure 2 is a side view of a listening environment including a system in accordance with an embodiment of the present invention.
  • Figure 3 is a block diagram of the system depicted in Figures 1-2.
  • Figure 4A is an illustration showing a speaker arrangement that can be employed in the system of Figures 1 and 2.
  • Figure 4B is a graph showing sound pressure level directivity patterns produced by the speaker arrangement of Figure 4A.
  • Figure 4C is a graph illustrating a frequency response of speaker driver channels within the system of Figures 1 and 2.
  • Figure 5A is a block diagram of a system in accordance with another embodiment of the present invention .
  • Figure 5B is a block diagram of a system in accordance with another embodiment of the present invention.
  • Figure 6 is a schematic diagram of a speaker circuit in accordance with still another embodiment of the present invention.
  • Figure 7A is an illustration depicting a DTV in accordance with an embodiment of the present invention.
  • Figure 7B is a block diagram of a calibration sub-system in accordance with an embodiment of the present invention.
  • FIG. 8 is a flowchart depicting a calibration method in accordance with an embodiment of the present invention.
  • BEST MODE FOR CARRYING OUT THE INVENTION The present invention encompasses systems and methods that include a pair of speaker drivers in a surround sound beam-forming process.
  • the speaker drivers have substantially differing frequency ranges, e.g., the woofer and tweeter of a 2-way speaker system or woofer and midrange driver of a 3-way speaker system, and main channel content is provided in a normal crossover fashion between the woofer and tweeter (and midrange) over the full audio range, so that the main channel information is propagated toward a listening area.
  • the main channel information is generally provided in a wide main directivity pattern that is provided on-axis to a listening area.
  • surround channel information is provided in a controlled-phase relationship in the overlapping frequency range of the speaker drivers that differs from that of the response of the drivers to the main channel information.
  • the differing controlled-phase relationship forms a second directivity pattern that is directed away from the listening area, so that most of the surround channel information is reflected at least once before reaching the listening area.
  • the surround channel information and main channel information are thereby superimposed on the listening environment in differing directions by two speaker drivers by virtue of a phase relationship between each driver that differs with respect to the main and surround channel signals in the overlap region.
  • the surround channel content is provided in a controlled phase relationship, which generally provides an on-axis null at the desired listening position, but due to the above crossover design considerations may be substantially in the same polarity or opposite polarity as the main channel information for overlapping response regions of the drivers away from the crossover frequency region of the main channel.
  • the surround channel information By directing the surround channel information away from the listening area, the surround content is heard only as diffuse reflections, providing the ability to simulate a surround sound listening environment from speakers positioned only at one end of a room. However, the speakers may be located at other positions in the room, with the surround channel directivity pattern increasing the diffusion by directing the surround channel information away from the listener.
  • the techniques of the present invention may be implemented in rear speakers of a 5.1 speaker configuration to provide a simulated 7.1 surround sound implementation.
  • the in-phase inputs (main channel inputs) of the speakers of the present invention can be connected to the side channel outputs of a receiver or other 7.1 surround sounds device and the controlled-phase inputs (surround channel inputs) of the speakers are connected to the back channel outputs of the receiver, providing an acoustic environment that is experienced as larger than the actual room size.
  • the system may be incorporated within an audio/video device having speakers included for the rendering of audio content, such as a DTV or computer monitor, or may be an audio-only device, such as a stereo system having internal speakers.
  • the system may also be incorporated in stand-alone speaker systems that include an internal electronic network that provides outputs to the speaker drivers to form a beam for direction of the surround channel information, or separate high and low frequency driver power outputs can be provided from another unit incorporating the electronic beam-forming network .
  • the illustrated system is an audio/video (AV) device 10 connected to an external stereo set of speakers 12L and 12R, each having a corresponding surround and main channel input coupled to AV device 10.
  • Each speaker 12L, 12R includes at least two drivers 14A, 14B and 14C,14D, respectively.
  • drivers 14A and 14C are tweeters for reproducing the high-frequency portion of the overall audio program.
  • Drivers 14B and 14D are woofers for reproducing the low-frequency portion of the overall audio program.
  • the illustration is exemplary only and the techniques of the present invention may be applied to other types of speaker systems having more than two drivers, including three-way speaker systems.
  • Each of speakers 12L, 12R includes an internal electronic network (not shown) that combines the main and surround channel signals received by each speaker in order to form two differing "beams" or differing directivity patterns.
  • the first beam which carries the main channel information, is generally the same as for an ordinary speaker, that is, driver pairs 14A, 14B and 14C, 14D are phase-aligned to reproduce the main channel information at a listening area directly in front of speakers 12L,12R.
  • driver pairs 14A, 14B and 14C, 14D are provided with surround channel information in a controlled phase/frequency relationship as between the drivers in each woofer/tweeter pair, so that a second directivity pattern directed away from the listening area is produced for the surround channel information.
  • the result is that the surround channel information is directed toward the walls, floor and/or ceiling of the room so that arrival of the surround channel information at the listening area is heard only as diffuse reflections .
  • FIG. 2 a side view of a listening environment including the system of Figure 1 is depicted.
  • the main channel information reproduced by speakers 12L, 12R propagates along a direct path 13A,B providing the first arrival of main channel sounds at a listening area 16.
  • the surround channel information is provided in an overlap region of frequencies reproducible by both tweeter drivers 14A, C and woofer drivers 14B,D of each speaker 12L, 12R and is phase-aligned in a substantially out-of-phase relationship as between tweeter driver 14A, C and woofer driver 14B,D in the overlapping frequency region so that a null is produced along direct path 13A,B.
  • the surround channel information is then propagated along path 17A, 17B.
  • the surround channel information is reflected at point 19A, 19B of ceiling 15 and is reflected toward listening area 16 and/or along paths 18A, 18B, which cause the surround channel information to arrive much later at listening position 16 and to be heard as diffuse (non-directional).
  • the vertical orientation of the speakers is not a limitation of the present invention, as in some embodiments of the invention disclosed in the above- incorporated parent U.S. Patent Application, and it is understood that horizontal orientation of speakers 12L, 12R will cause the surround channel information to be diffused by reflections from the walls of the room.
  • the surround beam-forming implemented in the system of the present invention uses a limited band of overlap frequencies that within the reproducible frequency range of both drivers 14A,B (and similarly
  • tweeter drivers 14A and 14C can only be used to a certain low-frequency cutoff without damage, although via protection mechanisms incorporated within embodiments of the present invention as detailed below, that low-frequency cutoff can be extended below the cut-off typically specified for the tweeter drivers.
  • tweeter drivers 14A and 14C should generally not be of a type incorporating internal protection capacitors.
  • the useful overlap range is limited at the high-frequency end by the response of woofer drivers 14B and 14D, which can be extended via the use of a "whizzer cone" type woofer and/or sufficient power amplification to overcome the loss of woofer response without amplifier clipping or overheating of the woofer coil. Further, the usable high- frequency overlap range is further limited by the spacing between drivers 14A and 14B (and similarly drivers 14C and 14D) due to "combing" or degeneration of the surround channel beam into multiple beams.
  • a DTV or another surround-enabled device 10 includes a program source 30, which may also be provided or selected from an external connection, that supplies a surround decode circuit 32 with program information.
  • Surround decode circuit 32 provides main channel and surround channel outputs to a frequency splitter/signal combiner network 34.
  • surround decode circuit 32 can include a surround synthesizer circuit for generating simulated surround information from a stereo program.
  • Frequency splitter/signal combiner network 34 divides the main channel information into high frequency and low frequency bands as in a standard active crossover network.
  • frequency splitter/signal combiner network 34 also combines the surround channel information to provide signals to the inputs of amplifiers A1-A4 such that the surround channel information is directed away from the listening position, while the main channel information is presented directly toward the listening position.
  • the outputs of amplifiers A1-A4 are provided to speaker drivers 14A-14D, which can be included within the cabinet of device 10 or optionally located in external speakers 12L and 12R, in which case the associated amplifiers A1-A4 may also be included within the cabinets of external speakers 12L and 12R and frequency splitter/signal combiner network 34 divided across two circuits, one in each speaker cabinet.
  • surround decode circuit 32 provides synthesized surround sound
  • the synthesizer circuits can be incorporated within external speakers 12R and 12L providing speakers that can synthesize a surround image from just a main channel signal. [0039] If amplifiers A1-A4 are included within device
  • frequency splitter/signal combiner network 34 may be made reconfigurable, so that use with traditional main and surround channel speakers can be selected for one "standard" operating mode, with the main and surround channel information amplified and supplied to external speaker connections. Then in another operating mode in accordance with an embodiment of the present invention, the external speaker connections are supplied as connections to high-frequency/low-frequency driver pairs as described above.
  • an audio/video receiver can be provided that in standard operating mode will perform as a standard AVR with power outputs and in a second operating mode provide power outputs for operation with a 2-way speaker system having separate terminals for each driver.
  • special external powered speaker cabinets may be provided that have separate line inputs for connection to each of amplifiers A1-A4, which are then provided within the external speaker cabinets.
  • An optional calibration circuit 38 may be included and connected to a microphone MIC input via a preamplifier PA.
  • Microphone MIC is ideally an omnidirectional microphone, so that all responses with respect to a given speaker or combination of speakers is detected during calibration.
  • the electronic network may be a pre-tuned or manually tunable digital or analog circuit that performs the phase alignment between the drivers. If pre-tuned external speakers are employed, the tuning is generally 180 degrees out of phase for the surround channel overlap frequency range, in-phase for the main channel and low- frequency surround, and high-frequency surround sent only to the tweeter.
  • calibration can also be performed with external speaker cabinets if the Left High, Left Low, Right High and Right Low are either provided via connections, in amplified or un-amplified form, to non- powered or powered external speakers, respectively.
  • separate calibration circuits may be included within external powered speakers.
  • driver 14A provides operation at higher frequencies and driver 14B provides operation at lower frequencies. Both drivers are active in the overlap beam- forming frequency range.
  • Driver 14A is generally a tweeter and driver 14B is generally a woofer. However, limited frequency responses in the drivers themselves is not required to practice the invention.
  • a simplified combiner 34A is shown for illustrative purposes that receives a Main channel signal and a Surround channel signal.
  • the signal provided to driver 14A combines the high-frequency portion of the main signal, a delayed and combined high-frequency portion of the surround channel signal, and the overlap frequency range portion of the surround signal.
  • the delayed high-frequency portion of the surround channel signal is provided so that any high- frequency content of the surround channel is not lost and is generally formed by summing the high-frequency portions of the surround channel signals from right and left after delaying them by different time delays. The result is a more diffuse (non-directional) presentation of the surround channel high-frequency information.
  • the signal provided to driver 14B combines the low-frequency portion of the main signal, the low- frequency portion of the surround channel signal, and overlap frequency range portion of the surround channel signal in opposite polarity to that supplied to driver 14A. There is no need to combine the right and left channel low-frequency information, as that information is generally non-directional.
  • combiner 34A operates as a standard crossover network for the Main channel signals and as a beam- forming network for the overlap frequency range portion of the Surround channel signal.
  • the overlap frequency range portion of the Surround channel signal is provided out-of-phase (as between drivers 14A and 14B in the overlapping frequency range) along the direct path to a listener located on-axis between drivers 14A and 14B, (e.g. directly in front of speaker 12L) thus producing a null with respect to the surround channel information toward the listener.
  • the listener will not hear the surround channel information as emanating from speaker 12L, but will hear the surround channel information as diffuse, coming from a range of reflection points primarily along the ceiling and/or the rear of the room.
  • the main channel information is provided in- phase (as between drivers 14A and 14B and normalized to whatever crossover polarity is employed) along the direct path, so that the main channel information is heard as emanating from the speakers.
  • the main and surround channel information are combined and are only supplied to driver 14B, and in the high- frequency range, the main channel information is provided only to driver 14A and the surround channel information delayed and combined across right and left channels to diffuse the sound.
  • a directivity pattern is shown for vertical orientation of the speaker arrangement of Figure 4A.
  • Directivity pattern A is shown as having a substantially cardioid shape and carries the main channel information, low frequency surround information and the diffused high frequency surround information.
  • Directivity pattern B has two lobes, one directed at the ceiling and one directed at the floor, due to the displacement of drivers 14A and 14B and the out-of-phase alignment of the surround channel information in the overlap frequency range.
  • the pattern of Figure 4B will be rotated to the azimuth, providing lobes in pattern B directed at the side walls of the room.
  • FIG 4C illustrates the frequency response of drivers 14A and 14B and the crossover filtering scheme of combiner 34A in which beam-forming is employed in the shaded overlap frequency band shown.
  • the crossover slopes (dotted lines) show the main channel crossover frequency locations, which differ from the overlap frequency range boundaries .
  • DSP digital signal processor
  • DSP 41 is coupled to a program memory 42 containing program instructions forming a computer program product in accordance with an embodiment of the present invention, and further coupled to a data memory 43 for storing data used by the computer program and results produced thereby.
  • the outputs of DSP 41 are depicted as pulse-width modulator (PWM) outputs for each channel, with corresponding low-pass filters and driver transistors 44, generally half-bridge circuits with series LC filters connected to drivers 14A-14D.
  • PWM pulse-width modulator
  • FIG. 5B a direct and surround channel circuit or algorithm in accordance with an embodiment of the present invention is shown in a block diagram. Only one stereo side (right or left) of the system is shown with respect to high frequency processing block 4OA and low frequency processing block 40B, as the other side will generally be an identical circuit. However a common high-frequency surround channel diffusion block 45 is shown that includes differing delays ⁇ ti, ⁇ t 2 a summer 48B to combine the delayed right and left surround channel signals and a high-pass filter 46C to provide the diffused high-frequency surround information to a combiner 48A within high-frequency processing block 4OA that supplies the signal provided to driver 14A through amplifier Al and tweeter protection compressor 49A.
  • High—frequency processing block 4OA also includes a crossover high-pass filter 46A for the main channel, an overlap frequency range filter 46B for the surround channel and a combiner 48A that combines the output of filter 46A, the inverted output of filter 46B, and the output of high-frequency surround channel diffusion block 45.
  • Optional finite impulse response (FIR) filters 47A and 47B provide for adjustment of main channel and surround channel phase vs. frequency response for calibrating the system.
  • Compressor 49A acts to prevent damage to driver 14A when low-frequency content would otherwise damage driver 14A.
  • Compressor 49A is especially desirably present since the characteristic of filter 46B or of FIR filter 47B is tailored to raise the level of lower overlap frequencies provided from driver 14A to match that of driver 14B for effective production of an on-axis null for the surround channel information.
  • Compressor 49A can be alternatively located between FIR filter 47B and combiner 48A in order to compress only the surround channel information within the signal provided to driver 14A.
  • Low—frequency processing block 4OB includes a crossover low-pass filter 46D for the main channel and an overlap frequency range filter 46E for the surround channel and a combiner 48C that combines the outputs of filters 46D and 46E.
  • the output of combiner 48C is combined with the non-inverted output of filter 46B from high-frequency processing block 4OA to provide an opposite phase version of the surround channel signal in the overlap frequency range to driver 14B via amplifier A2. While the illustrative structure of processing blocks 4OA and 4OB show identical polarity for the main channel information and opposing polarity, it will be understood that once crossover considerations are taken into account with respect to the main channel signal, the polarity of the main channel signal may well be reversed, as well.
  • the primary consideration is that the response of the main channel over frequency in the crossover region is uniform on-axis, while the response of the surround channel information produces a directivity pattern that is directed away from the on-axis listening position.
  • Optional FIR filters 47C and 47D provide for adjustment of main channel and surround channel phase vs. frequency response for calibrating the system.
  • An optional compressor 49B acts to prevent amplifier clipping when the increased gain of either filter 46E or FIR filter 47D raises the gain of low-frequency processing block 4OB with respect to the surround channel information in the higher-frequency portion of the overlap frequency range.
  • the channel circuit of Figure 5B is an example of an arrangement of blocks that implement an embodiment of the present invention or cascaded functions that can be applied in a DSP algorithm.
  • alternative implementations are possible and in some instances preferred.
  • all of the filtering functions could be performed within FIR filter blocks, with the in- phase/out-of-phase midrange beam-forming summations performed also within the FIR filter blocks.
  • speaker protection compression can be made part of the filter algorithm, as well.
  • a more generic expression of a channel circuit in accordance with an embodiment of the present invention can be made as a set of FIR filters each receiving either a Main or Surround channel signal and having output summed for forming the input signals to amplifiers Al and A2. Additional FIR filters for each discrete other speaker may be provided (e.g., center speaker or additional horizontally distributed speakers).
  • a traditional crossover provided by filters 46A and 46D can act without any FIR filter adjustment and a single FIR filter 47B or 47D can be used to calibrate or otherwise tune only the relationship between the overlap frequency range surround channel information provided to drivers 14A and 14B so that the on-axis surround channel null can be optimized and/or the position of the lobes in the surround channel beam directed to maximize the diffusion of the sound.
  • each speaker e.g., speakers 12L, 12R of Figures 1 and
  • a transformer Tl can be used with crossover elements to combine the surround channel information with the main channel information provided by two powered signals, such as main and surround channel outputs provided from a receiver that includes amplification.
  • a low-pass crossover filter provided by inductor Ll and capacitor Cl is series-connected with a winding of transformer Tl to supply a signal to low-frequency driver 14B.
  • the surround channel signal is provided to another winding of transformer Tl so that the surround channel information is added to the low-frequency main channel information supplied to driver 14B.
  • the series connection of the winding is in opposite phase with the winding receiving the surround channel signal.
  • High-frequency driver 14A receives the higher frequency main channel information coupled via a capacitor C2 and an in-phase version of the surround channel information coupled through resistor Rl and capacitor C3 from a third winding of transformer Tl.
  • the depicted network acts both as a crossover for the main channel signal and as an out-of-phase combiner for the surround channel signal, with capacitor C3 providing some level of protection for driver 14A via restriction of the lower-frequency end of the overlap frequency range.
  • Resistor Rl and capacitor C3 set the upper corner frequency of the range for which the surround signal is applied to driver 14A.
  • a three-way passive network can be similarly implemented with transformer Tl windings coupling a surround channel signal to woofer and midrange drivers, rather than woofer and tweeter as shown.
  • FIG. 7A illustrates one possible implementation of a 5.1 or 7.1 DTV system 70 and a consequent speaker arrangement.
  • DTV 70 includes driver pairs 14A,B and 14C,D and may further include a center speaker C, along with a center left CL and center right CR speaker.
  • a vertical beam-forming speaker array is provided as described above by internal driver pairs 14A,B and 14C,D and may also include external speakers 72A-B that may also have vertical or horizontal beam- forming woofer/tweeter arrangements.
  • a subwoofer/effects channel speaker SUB is located beneath DTV 70. The resultant combination increases the degrees of freedom possible in calibrating maximum surround channel effect via adjustment of the individual FIR filters in the DTV 70 internal processing circuits.
  • a calibration controller 64 in response to a user control of DTV 10 applies the output of a sequence generator 60 to frequency splitter/signal combiner network 34. Either one channel can be calibrated at a time, or multiple uncorrelated sequences can be provided to all channels for simultaneous calibration.
  • An adjustable delay 63 applies the sequence signal (s) to a correlator (or multiple correlators) 62 that correlate the sequence (s) with a microphone signal provided from detector 61. The arrangement permits calibration controller 64 to determine the impulse response of each channel at the microphone position.
  • the system can then be calibrated via the adjustment of the filter coefficients and/or overlap filter frequency response within signal combiner/filter network 34 to match the levels provided by the low-frequency drivers with the high-frequency drivers of each speaker for the overlap frequency range.
  • the system may also be calibrated to minimize the reverberant (reflected) energy with respect to the main channel inputs and maximize the reverberation with respect to the surround channel inputs, by adjusting the phase response of each driver with respect to the main and surround channel inputs.
  • the illustrated calibration system uses a sequence such as a maximal- length sequence (MLS) to extract the impulse response of the system, frequency sweeping, chirping or white/pink noise techniques may be similarly employed, with correlator 62 replaced with an appropriate filter.
  • MLS maximal- length sequence
  • FIG. 8 a flowchart depicting a calibration method in accordance with an embodiment of the present invention is shown.
  • the illustrated method is for a single channel calibration on each pass, but the multi-channel simultaneous calibration follows the same pattern.
  • an audio channel is selected and the tone, noise or sequence is generated through the corresponding channel (step 80) .
  • the listening position is monitored with a microphone (step 81) and if the channel under test is a main (direct) channel (decision 82), then the response of the channel filter is optimized to minimize the level of reflected energy (step 83) .
  • the overlap frequency range over which beam-forming is practical can be optionally determined (step 84) from the amount of boost required to match levels from the high-frequency and low frequency drivers and/or detection of the degradation of the null at the listening position due to combing at high frequencies or lack of driver spacing at low frequencies.
  • the above determination can be made via further selection of not only the channel in step 80, but selectively disabling the signal path to each driver from the selected channel by disabling the FIR filter that couples the channel to the associated driver channel.
  • the process from steps 80- 85 is repeated over each channel (or performed simultaneously) and also iterated until all filter sets have been calibrated and the values stabilized as between all of the channels (decision 86) .
  • the above-described calibration can be performed by summing the response of the high frequency driver in each driver pair with a time-delayed version of the lower frequency driver response. As the delay is varied, a delay is reached having the greatest surround effect, which is determined as the above-described maximum of the ratio of late response to early response.
  • the figure-of-merit is the ratio of late to early energy in the signal received at the microphone.
  • a reasonable cut-off time for considering energy late vs. early for a typical room, is energy arriving more than 5 ms after the initial impulse response (direct energy) for a single speaker is considered late energy.
  • the impulse response of the adjustable FIR filters in each channel can then be adjusted to accomplish the delay, which can be a frequency dependent delay for each driver.
  • the direct response can also be calibrated in a similar manner, with the delay determined to minimize the reflected energy and maximize the direct (non-reflected) energy.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Stereophonic System (AREA)
  • Circuit For Audible Band Transducer (AREA)

Abstract

Système de conformation de faisceaux sonores surround exploitant la partie de chevauchement des plages de fréquences des circuits d'attaque, et offrant une solution de rechange peu coûteuse au systèmes actuels à ensembles surround extérieurs. La plage chevauchement des fréquences d'une paire de circuits d'attaque de hauts-parleurs, en général un circuit d'attaque basse fréquence et un circuit d'attaque haute fréquence, reçoit des informations de canal surround selon une relation de phase commandée telle que lesdites informations se propagent selon un schéma de directivité sensiblement différent de celui des informations de canal principal fournies aux circuits d'attaque basse fréquence et haute fréquence. Les informations de canal principal sont généralement dirigées sur une zones d'écoute alors que celles de canal surround sont dirigées à l'écart de cette zone d'écoute de sorte qu'elles sont perçues comme un champ réfléchi diffus. Un réseau électronique commande la relation de phase de canal surround et combine les signaux principaux et surround via soit un circuit actif, soit un circuit passif.
PCT/US2007/067342 2006-04-28 2007-04-24 Procédé et système de conformation de faisceaux sonores surround exploitant la partie de chevauchement des plages de fréquences des circuits d'attaque WO2007127757A2 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US11/380,840 US7606380B2 (en) 2006-04-28 2006-04-28 Method and system for sound beam-forming using internal device speakers in conjunction with external speakers
US11/380,840 2006-04-28
US11/383,125 2006-05-12
US11/383,125 US7545946B2 (en) 2006-04-28 2006-05-12 Method and system for surround sound beam-forming using the overlapping portion of driver frequency ranges

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WO2007127757A2 true WO2007127757A2 (fr) 2007-11-08
WO2007127757A3 WO2007127757A3 (fr) 2008-12-04

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WO2011114252A1 (fr) * 2010-03-18 2011-09-22 Koninklijke Philips Electronics N.V. Système de haut-parleurs et procédé de fonctionnement de ce système
US8542854B2 (en) 2010-03-04 2013-09-24 Logitech Europe, S.A. Virtual surround for loudspeakers with increased constant directivity
EP2282556A3 (fr) * 2009-07-30 2014-07-23 Thomson Licensing Dispositif d'affichage et dispositif de sortie audio
US9264813B2 (en) 2010-03-04 2016-02-16 Logitech, Europe S.A. Virtual surround for loudspeakers with increased constant directivity
RU2575883C2 (ru) * 2010-03-18 2016-02-20 Конинклейке Филипс Электроникс Н.В. Акустическая система и способ ее работы
CN106664485A (zh) * 2014-05-05 2017-05-10 弗劳恩霍夫应用研究促进协会 基于自适应函数的一致声学场景再现的系统、装置和方法
CN106792289A (zh) * 2016-12-12 2017-05-31 深圳市艾特铭客科技有限公司 一种音响

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US5809150A (en) * 1995-06-28 1998-09-15 Eberbach; Steven J. Surround sound loudspeaker system
US5870484A (en) * 1995-09-05 1999-02-09 Greenberger; Hal Loudspeaker array with signal dependent radiation pattern

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US5598480A (en) * 1994-11-07 1997-01-28 Kim; Man H. Multiple output transformer network for sound reproducing system
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Publication number Priority date Publication date Assignee Title
EP2282556A3 (fr) * 2009-07-30 2014-07-23 Thomson Licensing Dispositif d'affichage et dispositif de sortie audio
US8542854B2 (en) 2010-03-04 2013-09-24 Logitech Europe, S.A. Virtual surround for loudspeakers with increased constant directivity
US9264813B2 (en) 2010-03-04 2016-02-16 Logitech, Europe S.A. Virtual surround for loudspeakers with increased constant directivity
WO2011114252A1 (fr) * 2010-03-18 2011-09-22 Koninklijke Philips Electronics N.V. Système de haut-parleurs et procédé de fonctionnement de ce système
CN102792712A (zh) * 2010-03-18 2012-11-21 皇家飞利浦电子股份有限公司 扬声器系统及其操作方法
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CN102792712B (zh) * 2010-03-18 2016-02-03 皇家飞利浦电子股份有限公司 扬声器系统及其操作方法
RU2575883C2 (ru) * 2010-03-18 2016-02-20 Конинклейке Филипс Электроникс Н.В. Акустическая система и способ ее работы
CN106664485A (zh) * 2014-05-05 2017-05-10 弗劳恩霍夫应用研究促进协会 基于自适应函数的一致声学场景再现的系统、装置和方法
CN106792289A (zh) * 2016-12-12 2017-05-31 深圳市艾特铭客科技有限公司 一种音响

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