Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S3/00—Systems employing more than two channels, e.g. quadraphonic
  • H04S3/002—Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S1/00—Two-channel systems
  • H04S1/002—Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution
• • 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
  • H04R2499/13—Acoustic transducers and sound field adaptation in vehicles

Definitions

• the field of the present invention relates to sound reproduction and, more
• the 5.1 surround format comprises a compressed data stream
• a low frequency effects channel is formed by a combination of the five other
• the 6.1 surround format includes the
• the 5.1 surround format has two surround channels (surround
• the 6.1 surround format has three surround channels (surround left, right
• the 7.1 surround format has four surround channels (surround left and right), and the 7.1 surround format has four surround channels (surround left and right), and the 7.1 surround format has four surround channels (surround left and right), and the 7.1 surround format has four surround channels (surround left and the 7.1 surround format has four surround channels (surround left and the 7.1 surround format has four surround channels (surround left and the 7.1 surround format).
• Basic surround system speaker configurations generally include from six
• a seven-speaker surround system typically includes the same speaker arrangement as the six-speaker surround system, but adds a back
• An eight-speaker surround system typically includes the same
• the sound volume may appear to increase as left/right
• signals are monaural, in order to provide an improved enveloping surround effect.
• surround speakers left and right are each fed with an identical monaural signal (that is,
• the sound may seem “unnatural"), a narrow “sweet spot” due to lack of
• nulls may be produced due to sound wave cancellation effects.
• loudspeaker type e.g., full range, satellite plus sub-woofer, dipole, monopole
• loudspeaker type e.g., full range, satellite plus sub-woofer, dipole, monopole
• the sound at off-axis listening positions may be sub-optimal.
• the quality of the sound at off-axis listening positions may be sub-optimal.
• the present invention is generally directed to improved sound
• a sound reproduction system comprises a pair of speakers
• processor acts to "spread" the sound image produced by the two closely spaced
• the resulting difference signal is scaled, delayed (if necessary) and spectrally modified before
• spectral modification to the difference channel preferably takes the form of a low-
• networks may be inserted in the difference channel to correct for any extra phase shift
• a linear-phase network may be employed to provide the
• sound stereophonic system may comprise a set of speakers (e.g., front, left, center,
• surround left, and surround right including a pair of surround back speakers located in
• the sound processor receives left and right
• surround channel signals (either side or rear surround signals), and generates a
• the resulting difference signal may be processed as
• the pair of central speakers may be any one of central speakers.
• the center speakers may be placed with their diaphragms facing down
• FIG. 1 is a diagram illustrating playback of a soundtrack in a 5.1 surround
• FIG. 2 is a diagram illustrating playback of a 5.1 surround format
• FIG. 3 is a diagram illustrating playback of a 6.1 surround format
• FIG. 4 is a diagram illustrating the concept of a "sweet spot" in the
• FIG. 5 is a diagram illustrating movement of the phantom image in
• FIG. 6 is a diagram of a speaker configuration for a surround sound
• FIG. 7 is a diagram illustrating 6.1 surround format playback in the
• FIG. 8 is a simplified block diagram of a sound processing system in
• FIG. 9-1 is a more detailed diagram of a sound processing system as may
• FIG. 9-2 is a diagram of a sound processing system in general accordance
• FIG. 10 is a diagram of a sound processing system illustrating
• FIG. 1 1 is a diagram of a sound system in accordance with the general
• FIG. 12 is a conceptual diagram illustrating processing/operation for 5.1
• surround format playback in the context of a surround sound system such as shown, for
• FIG. 6 example, in FIG. 6 or 1 1.
• FIGS. 13 and 14 are graphs illustrating examples of frequency response
• FIGS. 15-1 , 15-2, and 1 5-3 are graphs illustrating examples of gain and/or
• FIG. 16 is a diagram of a sound processor employing a linear spectral
• FIG. 1 7 is a diagram of a preferred automobile sound system in
• FIG. 18 is a diagram of a surround sound system for an automobile or
• FIGS. 19-1 , 19-2 and 19-3 are diagrams illustrating possible placement of
• FIG. 20-1 is a front cut-away view of a preferred speaker enclosure for a
• FIG. 20-2 is a top cross-sectional view of the speaker enclosure shown in
• FIG. 20-1 is an oblique front view of the speaker enclosure shown in
• FIGS. 20-1 and 20-2 are identical to FIGS. 20-1 and 20-2.
• FIG. 20-4 is a diagram illustrating sound reflection from a downward
• oriented speaker such as a speaker in the speaker enclosure of FIGS. 20-1 through 20-3.
• FIG. 21 is a block diagram illustrating an example of an automobile sound
• FIG. 22 is a graph illustrating a relationship between speaker separation in
• FIG. 23 is a diagram of another embodiment of a surround sound system
• FIGS. 24-1 and 24-2 are diagrams comparing the audio effect of speaker
• reproduction system comprises, in one aspect, a pair of speakers located in close
• the sound processor preferably acts to "spread" the sound image produced by the two
• cancellation signal is derived, for example, from the difference between the left and
• the resulting difference signal is scaled, delayed (if necessary) and spectrally modified before being added to the left channel and, in opposite polarity, to
• FIG. 1 is a diagram illustrating playback of a
• 5.1 surround system 100 includes a front left speaker 104, a front right speaker 105, a
• center speaker 102 center speaker 102, a sub-woofer 109, a surround left speaker 1 14, and a surround right
• right speakers 1 14, 1 1 5 are typically widely spaced on opposite sides of a room (or
• system 100 are generally arranged to provide optimum sound for a listener 107
• a 6.1 surround system adds a single rear surround speaker, while a 7.1 surround system adds two
• rear surround speakers typically spaced relatively far apart from one another.
• FIG. 2 is a diagram of a 7.1 surround system 200, illustrating playback of a
• a surround left speaker 214 a surround right speaker 21 5
• FIG. 1 the surround left and right speakers 214, 215 are dipolar in nature.
• surround back left and right speakers 224, 225 are typically spaced relatively far apart
• the surround left and right speakers 214, 215 are shown in FIG. 2, the surround left and right speakers 214, 215
• right speakers 224, 225 may or may not receive the left and right surround channel
• FIG. 3 is a diagram illustrating 6.1 surround format playback in a 7.1
• surround back speakers 324, 325 produces a central "phantom" sound image 330
• effects include "coloration" associated with the phantom sound image 330, which can
• system 300 can suffer significantly, particularly for listeners that are not positioned in an
• FIG. 6 is a diagram showing a speaker configuration for a surround sound
• system 600 of FIG. 6 includes, similar to the systems 200 and 300 shown in FIGS. 2 and 3, respectively, front left and right speakers 604, 605, a front center speaker 602, a sub-
• system 600 further includes a surround back left speaker 624 and a surround back right
• speaker 625 which are preferably positioned in close proximity to one another, possibly
• 625 are preferably identical and may be either dipolar or monopolar in nature, but are
• the speaker configuration of the sound system 600 is shown in FIG. 6 as monopolar.
• the speaker configuration of the sound system 600 is shown in FIG. 6 as monopolar.
• FIG. 6 coupled with a preferred sound processing technique, can provide
• channel audio signals are fed to the appropriate individual speakers, as would normally
• left and right speakers 624, 625 preferably receive the surround back right channel
• Surround EX playback is properly selected (e.g., a Surround EX
• the surround back left and right speakers 624, 625 both receive and respond directly to the surround rear channel audio signal.
• the monaural signal i.e., the surround rear channel audio signal
• the sound system may effectively treat the soundtrack as a 5.1 soundtrack
• the surround back left and right speakers are preferred sound system as disclosed herein, the surround back left and right speakers
• FIG. 7 illustrates the playback of
• audio signals are fed to both the surround left and right speakers 614, 61 5, and to the
• the surround left/right channel audio signals are monaural in nature, the sound system
• 600 preferably uses adaptive de-correlation to provide a de-correlated signal for the side
• surround speakers 614, 615 and provides a direct feed to the surround back left
• surround left/right channel audio signals are stereo in nature, the surround left/right
• channel audio signals are fed directly to the surround left and right speakers 614, 615
• surround left and right channel audio signals are processed such that the apparent rear
• FIG. 12 is a simplified diagram conceptually illustrating playback of a 5.1
• 600 is configured to apply the surround left and right channel audio signals 121 1 , 1212
• processing (as represented by blocks 1271 and 1272) is activated, and when they are
• any encoded program e.g., surround sound or multi-channel soundtrack
• any audio product or source is fed directly to the appropriate right and left speakers
• the pair of closely spaced speakers is thereby capable of generating a sound
• FIG. 8 is a generalized block diagram of a sound processing system 800 in accordance
• a left audio signal 81 1 and right audio signal 812 are provided to a left audio signal 81 1 and right audio signal 812 .
• audio signal 81 1 and right audio signal 812 may also be provided to left and right side (surround or non-surround) speakers, not shown in FIG. 8.
• left and right side (surround or non-surround) speakers not shown in FIG. 8.
• the sound processor 810 acts to "spread" the sound image produced by the two closely
• spaced speakers 824, 825 by employing a cross-cancellation technique wherein a
• cancellation signal is derived, for example, from the difference between the left and
• channel preferably takes the form of a low-frequency boost over a specified frequency
• effect of the sound processor 810 is to enlarge the perceived area and stability of the
• FIG. 9-1 is a more detailed diagram of a sound processing system 900 in
• a left audio signal 91 1 is generated in the sound processing system 900 of FIG. 9-1 .
• right audio signal 912 are provided from an audio source, and may be fed to other
• right audio signal 912 is obtained by, e.g., a subtractor 940, and the difference
• spectral weighting filter 942 which applies a spectral weighting
• the characteristics of the spectral weighting filter 942 may vary depending upon a number of factors including
• phase equalizer 945 which compensates for the phase
• the output of the phase equalizer 945 is provided to a cross-
• the cross-cancellation circuit 947 also receives the left audio
• phase compensation circuits 955, 956, which may be
• all-pass filters preferably shift the phase of their respective input
• phase shifting performed by the phase equalizer 945 (in combination with the phase
• cross-cancellation circuit 947 which may include a pair of summing circuits (one for
• each channel then mixes the spectrally-weighted, phase-equalized difference signal,
• the pair of speakers 924, 925 can be adjusted by varying the gain of the difference
• FIG. 9-2 is a diagram of a sound processing system 900' in general
• FIG. 9-1 further showing typical examples of possible transfer function characteristics for certain processing blocks.
• audio signal 912' are provided from an audio source (not shown), and a difference
• the difference signal 941 ' is fed to a spectral
• weighting filter 942' which, in the instant example, applies a spectral weighting to the
• FIG. 9-2 A more detailed graph of the transfer function characteristics (both
• the spectral weighting filter 942' is embodied as a first-order shelf
• gain/ amplifier block 946' can be
• a phase equalizer 945' is provided in the center processing channel, and
• phase compensation circuits 955' and 956' in the right and left channels, to
• instant example causes a phase distortion over at least the 200 Hz to 2000 Hz range.
• the phase equalizer 945' provides no gain, but modifies the overall frequency characteristic of the center channel.
• the phase compensation circuits 955' and 956' are provided.
• phase compensation is preferably selected, in the instant example, such that the
• phase characteristic of the center channel that is, the combined phase effect of the
• spectral weighting filter 942' and the phase equalizer 945' is approximately 180°
• circuits 955' and 956' preferably are configured to apply identical phase processing to
• phase equalizer 945' is embodied as a second-order all-pass filter
• phase compensators 955', 956' are each
• Q value may be used to increase the steepness of the phase drop-off, reducing the extent
• FIG. 1 1 illustrates another implementation of the sound system 900
• FIG. 1 1 elements labeled with reference numerals "1 1 xx" generally
• FIG. 10 is another diagram of a sound processing system 1000, in
• signals X1 and X2 are processed along two parallel
• Y1 and Y2 respectively (which may be fed to a pair of speakers, e.g., left and right
• audio signal X1 is also fed to a processing block 1055 having a transfer function A, and
• processing block 1055 is added together with the output of processing
• X2 is fed to a processing block 1056 having a transfer function -A (i.e., the inverse of
• the transfer function -B of processing block 1060 represents
• phase equalizer such as illustrated by the difference path in the sound processing
• processing blocks 1055 and 1056 respectively, each represent the transfer function
• phase compensation network that performs a complementary phase shifting
• FIG. 10 are selected so that appropriate cross-cancellation will be attained.
• input signals X1 and X2 represent the Z-
• A, -A, and B may be represented in terms of z, and are determined in part by the
• sampling frequency Fs associated with processing in the digital domain.
• blocks 1055 and 1056 are each second-order all-pass filters with
• block 1060 may be a first-order shelf having a gain of 0
• a gain factor may also be included in block 1060, or else may be provided in the same
• the gain may be determined for a particular
• the gain factor is 12 dB.
• FIGS. 13 and 14 are graphs illustrating examples of frequency response
• FIG. 13 illustrates a frequency response transfer function 1302
• phase transfer function 1305 for — B/A which represents the transfer function of the
• the frequency response transfer function 1302 exhibits a relatively flat
• phase response transfer about 200 Hertz to about 2 KHz), and then a relatively flat gain again in a third region 1322 of high frequencies (in this example, above 2 KHz).
• function 1305 indicates that in the second region 1321 of mid-range frequencies (i.e.,
• the output signal remains substantially in phase.
• FIG. 14 illustrates a frequency response transfer function 1402 and phase
• transfer function 1405 for — B/—A which represents the transfer function of the
• response transfer function 1405 indicates that in the second region 1421 of mid-range
• inverted in phase i.e., at 180 degrees.
• the output signals Y1, Y2 are preferably provided to a pair of
• the transfer functions A, -A, and B are examples
• FIG. 16 is a diagram of a sound processing system 1600 in accordance
• a left audio signal 161 1 and right audio signal 1612 are processed to derive a pair of processed audio
• the left and right audio signals 161 1 , 1612 are operated
• spectral weighting filter 1641 is fed to a spectral weighting filter 1642 having a linear phase characteristic.
• spectral weighting filter 1642 may have frequency response characteristics in general
• weighting filter 1642 may be provided directly to a cross-cancellation circuit 1646,
• components 1655, 1656 preferably have a delay characteristic equal to the latency of
• various embodiments generally determines the amount of "spread" of the sound image.
• the pair of speakers e.g., speakers 824 and 825 in FIG. 8, or closely
• processed information are preferably located immediately adjacent to one another;
• performance may gradually decline as the speakers are moved farther apart from one
• the two speakers are placed no further apart than a distance that is
• implementations of the invention may, in some circumstances, be applicable to personal
• vehicular audio systems portable stereos, televisions, radios, and any other context in
• the pair of closely spaced left and right speakers may be part of an integrated portable stereo unit, or else may be located
• Automobile or vehicular audio systems may benefit from
• Audio systems are
• absorbtive areas such as the upholstery or the occupants clothing leads to a
• the listening positions are necessarily restricted to the seating positions
• the perceived spectral balance is different for each channel due to the
• an occupant can partially mitigate the aforementioned problems. For example, an occupant can
• sound problems include adding more speakers in a greater variety of positions (e.g., at
• a preferred automobile sound reproduction system comprises a pair of
• the sound reproduction system further preferably comprises a sound processor
• the sound processor acts to
• difference channel preferably takes the form of a low-frequency boost over a specified
• a linear-phase network may be employed to provide the
• the pair of central speakers may be placed in a
• the front console or dashboard of the automobile In certain embodiments, the rear console or dashboard of the automobile.
• center speakers may be placed with their diaphragms facing down and in close
• radiating system provides the dual benefit of occupying less dashboard area, where
• central speakers with similar sound processing may be added in the rear of the vehicle, for example in the center above the rear seatback, for use in the play back of program
• a pair of front central speakers may be used in both
• FIG. 1 7 is a diagram of a preferred automobile sound system 1 700 in
• speakers 1 714, 1 715 are positioned in close proximity to one another, and receive and
• the speakers 1 714, 1 715 are preferably left and right speakers, may (but need not) be
• the speakers 1 714, 1 715 may be positioned along or near the central axis of the interior
• dashboard or in a central island between the driver and passenger seats.
• the sound processor 1 708 receives audio input signals 1 702 and 1 703
• components e.g., CD player, cassette player, radio, etc.
• the audio input signals 1 702, 1 703 may be derived from any audio product
• any digital audio signal including any prerecorded medium (such as a cassette, CD, or DVD), any digital audio
• the sound processor 1 708 preferably processes the stereo sound signals 1 702, 1 703 according to
• the stereo signals 1 702, 1 703 may also optionally be fed, either
• the sound processor 1 708 acts to effectively
• the speakers 1714, 1715 are placed close together, side-by-side, the resulting
• phase shifting which can be compensated for using phase
• Complementary phase compensation can be provided along each of the
• audio channels 1 702, 1 703 prior to mixing (i.e., cross-cancellation) so that the left and
• right audio channels 1 702, 1 703 are substantially in phase with the spectrally modified
• the primary purpose of the speakers 1714, 1715 is
• pass filter may be utilized to prevent high-level, low-frequency signals from overloading
• 1 702, 1 703 can be fed to left and right bass speakers 1 721 and 1 722, respectively,
• dashboard or otherwise on or near the center axis of the automobile, they may (but
• 1 714, 1 71 5 are located at an ideal or at least preferably acoustical position, being less
• the pair of speakers (e.g., speakers 1 714 and 1 715 in FIG. 1 7) which
• receive the sound processed information are preferably located immediately adjacent to
• the farthest maximum separation of the speakers 1 714, 1 71 5 can be determined by
• the pair of speakers 1 714, 171 5 are
• the front console may, for example, may be inserted into or else integral with the front console or
• dashboard of an automobile or placed elsewhere near the central axis of the
• FIGS. 20-1 , 20-2, and 20-3 illustrate one example of an enclosure 2001
• FIG. 1 A block diagram illustrating right audio channels in accordance with the various techniques described herein.
• 20-1 is a front cut-away view of the exemplary speaker enclosure 2001 housing the pair
• FIG. 20-2 is a top cross-sectional view of the speaker enclosure
• FIG. 20-3 is an oblique front view of the speaker
• speaker enclosure 2001 in this example is preferably substantially rectangular in shape
• the speaker enclosure 2001 may include a front panel 2032, a pair of side
• an interior wall 2016 such as
• FIG. 20-1 and 20-2 may be placed between the speakers 2014, 2015,
• the pair of speakers 2014, 2015 may be pointed directly frontwards
• the speakers 2014, 201 5 are oriented downwards, as illustrated in FIG. 20-1.
• a slot 2019 may be located at the bottom of
• the speaker enclosure 2001 to allow the sound from the speakers 2014, 2015 to radiate
• Audio system controls/display(s) or other conventional
• console accouterments (controls, LCD or other displays, air vents, etc.) can be attached
• each speaker may be any speaker.
• center speaker unit allows better bass reproduction and, hence, reduces or potentially
• FIG. 20-4 shows a generic speaker 2090 pointing
• a slot 2019 is
• the speakers 2014, 2015 to radiate outwards towards the direction of the listeners in the
• a layer of insulation 2012 e.g., foam
• a layer of insulation 2012 preferably matching the outer
• contours of the speakers 2014, 2015, as illustrated in FIG. 20-2 may be placed within
• the speakers 2014, 2015 might be directed
• the speakers 2014, 2015 may
• speaker enclosure may be taller but narrower in size.
• one or more additional speakers 201 7 of small size e.g.,
• tweeters may be advantageously placed above the “bell” of the speakers 2014, 2015
• speaker enclosure 2001 may be positioned in other areas of the automobile as well,
• the closely spaced speakers 1 714, 1 715 are located on or near the center axis of the
• speakers may be of limited size. Smaller
• bass speakers e.g., speakers 1 724, 1 725 may be provided in a suitable location - for
• left and right door speakers can be processed to attenuate the mid/high frequencies
• a sub-woofer may be added in a suitable
• the sub-woofer may be located, for example, in the rear console of the vehicle
• placed in the front console or area can also be placed in the rear of the automobile, for
• a speaker enclosure 2001 such as shown in FIGS.
• FIG. 19-1 is a simplified top view of an automobile 1900 illustrating an
• speaker enclosure in the front section of the automobile 1900 (e.g., in the front console
• FIG. 19-2 illustrates an
• FIG. 19-3 (whether or not in a speaker enclosure) in the rear of the automobile 1920.
• driver compartment 1941 the driver compartment 1941 .
• FIG. 19-1 layout is similar to FIG. 19-1 , with a pair of closely spaced speakers 1945 in the front
• any number of additional speakers and audio components may be added
• system 2100 illustrates the feed of left and right audio signals 2102, 2103 to left and
• the left and right audio channels 2102, 2103 grows, the signal fed into the left or right
• right audio channels 2102, 2103 indicates an extreme left or right sound, which, in the
• Another embodiment directed to a surround or multi-channel sound
• FIG. 18 A block form in FIG. 18.
• the sound system 1800 may include an audio signal source 1805 which is shown therein, the sound system 1800 may include an audio signal source 1805 which is shown therein, the sound system 1800 may include an audio signal source 1805 which is shown therein, the sound system 1800 may include an audio signal source 1805 which is shown therein, the sound system 1800 may include an audio signal source 1805 which is shown therein, the sound system 1800 may include an audio signal source 1805 which is shown therein, the sound system 1800 may include an audio signal source 1805 which
• processor 1808 which functions in a manner similar to sound processor 1 708 shown in
• FIG. 1 or various other sound processor embodiments described herein with respect to
• the left and right audio signals 1802, 1803 are closely spaced left/right central speakers.
• the left and right audio signals 1802, 1803 are closely spaced left/right central speakers.
• a center audio signal of the surround sound is
• formatted medium may be mixed into the signals 1832, 1833 provided to the closely spaced speakers 1814, 1815, and may also be provided to additional center speakers
• additional speakers 181 7 may be embodied and arranged, for example, in the form of
• FIGS. 20A - 20C A surround left
• surround right audio channel 1871, 1872 may be fed into surround left and right
• speakers 1824, 1825 which may be dipolar or monopolar in nature.
• right speakers 1824, 1825 may be generally used to provide ambient sound.
• the surround left and right audio channels 1871 , 1872 are monaural in nature, adaptive
• Left and right speakers 1834, 1835 which may be, e.g., door-mounted
• speakers may be directly fed the left and right audio channels 1802, 1803, or else may
• FIG. 21 is a diagrammatic representation of FIG. 21.
• the sound system 1800 of FIG. 18 may further be provided
• the additional pair of closely spaced speakers may be fed the same processed
• left and right audio channel signals 1832, 1833 as provided to the front closely spaced
• speakers 1814, 1815 may be fed similarly processed signals derived from the
• FIG. 23 is a diagram of a surround or multi-channel sound system 2300
• a rear surround processor 2398 receives as inputs two
• rear surround processor 2398 preferably provides sound processing to the two surround
• the sound processing for the surround back speakers 2394, 2395 need not be
• speakers 2314, 2315 may serve a different purpose to some degree than the front
• the content of the surround back channels 2392, 2393 may depend upon
• the format of the encoded audio product In 5.1 surround format, for example, the
• surround back channels 2392, 2393 may be the same as the right and left surround
• channels 2392, 2393 are preferably the independent left and right surround back
• the audio product e.g., soundtrack
• a home theater surround sound system for example, a home theater surround sound system
• automobile sound system may be capable of providing quality sound to a greater
• system components may comprise any audio work of any nature, such as, for example
• a musical piece a soundtrack to an audio-visual work (such as a DVD or other
• the audio product may be read from a recorded medium, such as a DVD, cassette,
• compact disc CD-ROM, or else may be received wirelessly, in any available format,
• the audio product preferably has at
• additional channels may, for example, be encoded in a surround sound or
• product may also comprise digital files stored, temporarily or permanently, in any format used for audio playback, such as, for example, an MP3 format or a digital multi-media
• circuit either digital or analog techniques, or any combination thereof.
• DSP digital signal processing
• embodiments may be programmable so as to allow tailoring to suit individual sound
• spectral weighting shape is preferably selected to take account of the physical
• the pair of closely spaced speakers may be forced

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• 2002
  • 2002-02-08 EP EP02717406A patent/EP1360874B1/en not_active Expired - Lifetime
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  • 2002-02-08 WO PCT/US2002/003880 patent/WO2002065815A2/en active Application Filing
  • 2002-02-08 JP JP2002565394A patent/JP2004521541A/ja active Pending

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