US3821471A - Apparatus for reproducing quadraphonic sound - Google Patents

Apparatus for reproducing quadraphonic sound Download PDF

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US3821471A
US3821471A US00124135A US12413571A US3821471A US 3821471 A US3821471 A US 3821471A US 00124135 A US00124135 A US 00124135A US 12413571 A US12413571 A US 12413571A US 3821471 A US3821471 A US 3821471A
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signals
signal
phase
control
operative
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US00124135A
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B Bauer
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Sony Music Holdings Inc
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CBS Inc
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Priority to US00124135A priority Critical patent/US3821471A/en
Priority to CA133,379A priority patent/CA978860A/en
Priority to GB841272A priority patent/GB1387874A/en
Priority to DE2209424A priority patent/DE2209424C3/de
Priority to NL7203169A priority patent/NL7203169A/xx
Priority to JP47024794A priority patent/JPS5110962B2/ja
Priority to FR7209094A priority patent/FR2130306B2/fr
Priority to BE780710A priority patent/BE780710R/xx
Priority to FR7209093A priority patent/FR2130305B2/fr
Priority to BE780711A priority patent/BE780711R/xx
Application granted granted Critical
Publication of US3821471A publication Critical patent/US3821471A/en
Priority to JP8911275A priority patent/JPS5316281B2/ja
Assigned to CBS RECORDS, INC., 51 WEST 52ND STREET, NEW YORK, NEW YORK 10019, A CORP. OF DE reassignment CBS RECORDS, INC., 51 WEST 52ND STREET, NEW YORK, NEW YORK 10019, A CORP. OF DE ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: CBS INC.
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S3/00—Systems employing more than two channels, e.g. quadraphonic
    • H04S3/02—Systems employing more than two channels, e.g. quadraphonic of the matrix type, i.e. in which input signals are combined algebraically, e.g. after having been phase shifted with respect to each other

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  • This invention relates to apparatus for recording and reproducing four separate channels of information on a medium having only two independent tracks, and more particularly to improved methods and apparatus for reproducing such information and presenting it on four loudspeakers to give the listenerthe illusion of sound coming from a corresponding number of separate sources. More particularly, this'invention is concerned with an improved decoder for four'channel sound recorded on a two-track medium in accordance with the method described in the aforementioned copending application Ser. No. 328,874.
  • the recording method disclosed in application Ser. No. 328,874 is based on an encoding function which results from passing four signals associated with the four channels of sound (which, for convenience, are identified as 1 L Rf and R for left-front, leftback, right-front and right-back, respectively) through six all-pass phase-shifting networks and thereafter combining them in appropriate proportions to produce two composite signals, L and R
  • the encoder of the aforementioned application, illustrated in FIG. 1, has four input terminals 10, 12, 14 and 16, to which are respectively applied signals four channels of a quadru- .phonic program, L L,, R and R;, which are represented by phasors 18, 20, 22 and 24, respectively.
  • a phasor generally represents a sinusoidal wave of a particular frequency, with the length of the phasor arrow portraying its amplitude and its direction representing the phase angle.
  • the four phasors are shown as all being of equal amplitude and direction.
  • the positions of the individual phasors are modified by a plurality of all-pass phase-shifting networks 26, 28, 30, 32, 34 and 36 which have the capability of transmitting all of the frequencies within the range of interest (typically, the full audio range from 20 to 20,000Hz.) without change in amplitude but with a change of relative phase, which includes a reference phase-shift ill, which is a function of frequency, and adifi'erential phase-shift which may be any desired angle, typically 45 or 90.
  • the all-pass networks 26 and 36 (hereinafter called ill-networks) 28 and 34 provide aphase-shift of II! 45
  • networks 30 and 32 provide a phase-shift of II! 90.
  • the L; signal is applied to network28, the L signal is applied to both of networks 26 and 32, signal R is applied to both of networks 30 and 36, and signal R is applied to network 34.
  • signals 1 and R representing the total left and right channel signals, respectively, may be broadcast through an FM-multiplex transmitter and received with an FM-stereo receiver for subsequent decoding, or they may be recorded on a twotrack medium, such as a stereophonic phonograph record or two-track tape, for subsequent replay and decoding, all as explained in No. 328,874.
  • FIG- 2 illustrates how the signals encoded with the system of FIG. 1 are recorded on an ordinary stereophonic record 50 having a groove 52 in the surface 54 thereof cut by a recording stylus for subsequent replay in a well-known manner.
  • the left channel of a stereophonic record causes modulation of the inner groove wall, that is, the groove wall nearest to the center of the record, with the motion at 45 to the surface as portrayed by the arrow 1 and the right channel causes modulation of the other groove wall, that is, the wall furthest from the center, causing it to move at 45 to the surface, as indicated by the arrow R
  • the left channel of a stereophonic record causes modulation of the inner groove wall, that is, the groove wall nearest to the center of the record, with the motion at 45 to the surface as portrayed by the arrow 1
  • the right channel causes modulation of the other groove wall, that is, the wall furthest from the center, causing it to move at 45 to the surface, as indicated by the arrow R
  • Another object of the invention is to provide a system for encoding four sound channels into two composite signals which avoids exaggeration of output signal intensity upon decoding when equal signals are applied to the side terminals (e.g., left-front and left-back) of the encoder.
  • Another object of the invention is to provide a system including an encoder for encoding four sound channels into two composite signals and a decoder for use therewith capable of resolving ambiguities in reproduction caused by the appearance of equal signals on the two front channels, or on the two back channels.
  • Still another object is to provide an encoder having the foregoing features and advantages while at the same time simplifying and reducing the cost of circuitry for accomplishing them.
  • the four input signals as L;, L,,, R and R, (for left-front, left-back, right-back and right-front), they are combined in such a manner that both the left and right composite signals contain subdominant signals L,, and R, in quadrature relationship, and respectively contain dominant L; and R; components which are in phase with each other and also in phase with their associated R and L,, components, respectively.
  • the L component leads the R component in the left composite signal and lags the R component in the right composite signal
  • the L,, component lags the R component in the left composite signal and leads the R component in the right composite signal.
  • the composite signals in both cases upon decoding, produce four predominant signals which are all in phase, and also have characteristics which avoids exaggeration of output signal intensity when equal signals are applied to the side terminals (e.g., left-front and left-back) of the encoder.
  • the'encoder comprises an arrangement of phase-shifting networks and summing circuits which again causes subdominant L and R components'to appear in quadrature relationship in both the left and right composite signals, with the L component leading the R component in the left composite signal and lagging the R component in the right composite signal, and the dominant L; and R, components to be in phase with each other, but in this case, the L component is out of phase with its associated subdominant R component while the R, component is in-phase with its associated subdominant L component.
  • This phase relationship of the signal components in the left and right composite signals makes it possible to resolve ambiguities in situations when the sound signals are panned; that is, inserted into adjacent channels in an in-phase relationship.
  • decodingapparatus which includes a matrix for decoding the composite signals to recover the four separate signals for presentation on four separate loudspeaker systems, particularly in the addition of further logic to the decoder control logic described in the aforementioned Bauer application Ser. No. l18,27l which is responsive to the composite signals produced by the lastdescribed encoder to distinguish betweenfront and back signals and to promptly and automatically adjust the gain of the front and back loudspeakers to enhance the realism of four-channel reproduction.
  • FIG. 1 is a schematic diagram of the encoder described and claimed in co-pending application Ser. No. 44,224, to which reference has been made in discussing the background of the invention;
  • FIGS. 2 and 3 illustrate the operation of the encoding apparatus of FIG. 1;
  • FIG. 4 is a pair of phasor diagrams useful in explaining the principles of the present invention.
  • FIG. 5 is a schematic diagram of encoding apparatus embodying the invention.
  • FIG. 6 is a schematic diagram of decoder apparatus described in co-pending application Ser. No. 1 18,271, useful in explaining the efficacy of the present encoding technique;
  • FIG. 7 is a schematic diagram of an alternative form v of encoding apparatus embodying the invention.
  • FIG. 8 is a schematic diagram of still another alternative form of encoding apparatus embodying the invention.
  • FIG. 12A is a schematic diagram of a modification of the system of FIG. 12.
  • FIG. 13 is a schematic diagram illustrating how four original sound channels may be produced for recording and reproduction in accordance with the invention.
  • the present invention is based on the discovery, illustrated in FIG. 4, that while it is important in the encoding process to maintain a 90 relationship between the phasors 0.707L and O.707R the relative positions of the phasors L, and R; may be arbitrarily chosen insofar as decoding is concerned.
  • any decoder designed to decode the composite signals L and R in FIG. 1 (such as the decoder described and claimed in co-pending application Ser. No. l l8,27l will also satisfactorily decode the signals L and R shown in FIG. 4, regardless of the size of the angles'a and (1 between phasors L; and 0.707L and between phasors R; and 0.707R respectively.
  • the encoder in accordance with the invention has four input terminals 60, 62, 64 and 66 to which input signals L L R and R; originating with the quadruphonic program, and represented by phasors corresponding to the same signals depicted in FIG. 1, are respectively applied. Rather than being applied directly to a ill-network as in the system of FIG.
  • input terminals and 64 are connected to a summing junction 68 which is operative to add a unity measure of signal L, to .707 of signal component R
  • terminals 62 and 66 are connected to a second summing junction 70 which is operative to add a unity measure of signal R, to 0.707 of signal L
  • Terminal 62 is also connected to the input of ill-network 72 which introduces a relative phase-shift of II! to the signals L
  • terminal 64 is connected to the input of a second (ab 0) network 78.
  • the outputs of summing junctions 68 and 70 are respectively applied to the input tenninals of ill-networks 74 and 76, both of which introduce a relative phase-shift of 111 90.
  • FIG. 5 That the encoder of FIG. 5 is compatible with decoders intended for use with the signals encoded in accordance with the system of FIG. 1 is demonstrated by the comparative analysis presentedin FIG. 6, as applied to the decoder described in co-pending application Ser. No. 1 18,271.
  • This decoder includes a pair of input terminals and 102 to which composite signals L and R are respectively applied.
  • the signal applied to terminal 100 is applied in parallel to and phase-shifted by a pair of ill-networks 104 and 106, and the composite R signal applied to input terminal 102 is applied in parallel to ill-networks 1 08 and 110.
  • Equal portions of the outputs of networks 106 and 110 are summed in a summing junction 116, the output of which is applied to the left-back output terminal 118, and equal portions of the outputs of networks 104 and 108 are summed in a second summing network 120, the output of which is applied to the right-back output terminal 122.
  • Phasor groups and 132 portray the two input signals I and R which, upon being shifted in phase by the all-pass networks 104, 106, 108 and 110 appear as new phasor groups 134, 136, 138 and 140.
  • the phasors in these latter four groups are labeled with a prime-to differentiate them from the corresponding phasors prior to'introduction of the relative phase-shifts.
  • the signal represented by phasor group 134 appears at output terminal 112 as 7 phasor group 142 and contains a dominant component L, together with the smaller components O.707L and 0.707R
  • the phasor groups 136 and 140 after summing in junction 116 result in a signal at output terminal 118 represented by phasor group 144 containing a dominant phasor L and subsidiary phasors 0.7071 and 0.707R
  • the sum of phasors 134 and 138 appearing at the output of summing junction 120 (output terminal 122) is a composite signal represented by phasor group 146 having a dominant phasor R accompanied by subsidiary signals 0.707R, and 0.707L,.
  • the phasor group 140 appears at output terminal 114 as phasor group 148, and contains a dominant signal R,
  • the decoded signals appearing at output terminals 112, 118, 122 and 114 each contains its appropriate dominant signal together with signals from two other channels diminished by the factor O.707.
  • the two principal front channel phasors, namely L, in group 142 and R, in group 148 are in phase
  • the two principal back channel vectors, L,, in phasor group 144 and R, in group 146 are also in phase with each other, but not in phase with the L, and R, phasors. While this phase relationship does not represent a major flaw in the performance of the system, it has been found preferable that the four predominant phasors all be in phase.
  • These output signals contain predominant signals L, and R,, respectively, which are in phase with each other, and each includes subsidiary signals O.707R and 0.707L
  • the phasor groups 156 and160 upon being summed in summing junction 116- produces at output terminal 118 the composite signal portrayed by phasor group 166, and the sum of the signals represented by phasor groups 154 and 158 appearing at the output terminal 122 of summing junction 120 is as portrayed by phasor group 168.
  • phasor groups 166 and 168 contain predominant phasors L and R respectively, which are in phase with each other, and also in phase with the predominant phasors in groups 162 and 164, and each accompanied by two-subsidiary signals 0.707R/ and -O.707L
  • Comparison of phasor groups 162 with 142, 166 with 144, 168 with 146, and 164 with 148 reveals that they contain the same respective subsidiary signals in the same magnitude and in the same intergroup phase relationships. Therefore, the respective signals will be capable of properly activating the enhancing logic and control circuits described in co-pending applications Ser. Nos.
  • the improved encoder of FIG. 5 offers three significant advantages over the encoder of FIG. 1: 1) it provides encoding with four, instead of six ill-networks, with an attendant reduction in the cost of the encoder; 2) it produces encoded signals which, upon decoding, cause the predominant signals to all be in phase; and 3) it avoids exaggeration of output signal intensity from the decoder when equal signals are applied to the side terminals of the encoder.
  • FIG. 7 illustrates a modification of the encoder of FIG. 5, differing therefrom in the manner in which the four input signals are added and phase-shifted.
  • the full L; signal applied at terminal 170 is added to 0.707 of the R signal applied to input terminal 174 in a summing junction 178
  • the full R, signal applied at input terminal 176 is added in summing junction 180 to 0.707 of the L, signal applied at input terminal 172.
  • the sum signals from summing junctions 178 and 180 pass through respective til-networks 182 and 184 and are added in respective summing junctions 186 and 188 to 0.707 of signals L and R,,, respectively, after being shifted in phase by II!
  • the L and R signals appearing at output terminals 194 and 196, represented by phasor groups 198and 200, respectively, are similar to the corresponding phasor groups 88 and 90 in FIG. 5 except that in group 198 the 0.707R phasor leads the O.707L,, phasor, wherein in group 88 the L phasor v leads the'R phasor; the positions of the L and R phasors in groups 200 and are similarly interchanged.
  • angles a, and er of 90 are preferred, it may be desirable in some cases to chose other values, for example, 0 or 180, or a, and a may be different, as will now be obvious to those skilled in the art.
  • the contaminating signals are not noticed when all four predominant signals are simultaneously present, as when four different performers produce four parts of a musical selection in all four channels, since there is sufficient mixing of sound in the room or listening area that the presence of the contaminating signals in the individual channels is inconsequent'ial. They are noticable, however, when sound is present in only a single channel, or in at most two channels, because in these instances, when the sound should be coming from a single loudspeaker or from two loudspeakers, it is instead heard from all four, which is readily noticable and sometimes objectionable. This situation is improved, and the realism of four channel reproduction enhanced by the logic and control systems described in the aforementioned co-pending applications Ser. No.
  • the logic functions to enhance the gain of the front loudspeaker amplifiers and to turn down the gain of the back loudspeaker amplifiers thereby to cause the sound to appear to-originate at the left-front loudspeaker only.
  • the logic and control circuitry operates similarly with respect to the other three loudspeakers with the consequence that when artists are performing in concert in all four channels the gain of the respective amplifiers are increased and decreased to instantaneously enhance the channel or channels in which signals are predominant at a particularly instant to give a highly realistic replication of the original four channel program.
  • this ambiguity is resolved by modification of the encoder and the decoder, thereby to provide a significant improvement in performance of the system.
  • the modified encoder illustrated in FIG. 8, has four input terminals 210, 212, 214 and 216 to which the four signals L,, L,,, R), and R,, depicted as in-phase signals of equal amplitude, are respectively applied.
  • the total L; signal is added in a summing junction 218 to 0.707 of the R signal, the output of the summing junction being applied to a phase-shifting network 220 which introduces a reference phase-shift 111, which is a function of frequency.
  • the full R, signal at terminal 216 is added in summing network 222 to 0.707 of the L signal appearing'at input terminal 212, and the output is passed through the (II-network 224, which also provides the reference phase-shift ill.
  • the L, and R signals are also applied to respective lll networks 2'26 and 228, each of which provides a phase-shift of 1!;
  • the full signal appearing at the output of network 220 is added in a summing circuit 230 to 0.707 of the signal appearing at the output of network 226 to produce at its output terminal 232 a composite signal designated L
  • the full signal from network 224 is added in summing junction 234 to 0.707 of the signal from network 228, the latter in this case being in the positive sense.
  • the signal appearing at the output terminal 236 is the composite signal designated R
  • the signals L and R? may be transmitted by FM multiplex radio, or they may be recorded on any two-channel medium such as a two-track tape or stereophonic record-for later reproduction.
  • phasor group 238 consists of the signal L; (which although shown in the same phase relationship as the input signal L, has a rIJ-as-a-function-offrequency angle difference between them), a signal 0.707R, in a negative sense with respect to its corresponding input phasor, and a 0.707L signal which lags phasor 0.707R by 90 because of the action of network 226.
  • Phasor group 240 consists of the original signal R, in the same relative phase position as its corresponding input signal, a signal 0.707L in phase with the R; signal, and a .707R signal lagging the 0.707L signal by 90 due to the action of til-network 228.
  • the left groove is modulated during the cutting process in the direction of the arrow L (which is at 45 to the surface of the record) under the influence of the left-channel signal L while the groove is modulated in the direction of the arrow R under the influence of the rightchannel signal R
  • the effect of the panning is to divide the signal (as by means of two coupled attenuators) between two channel inputs. At the midpoint of the panning operation, the signal becomes precisely divided between the front channels L, and R or between the back channels L or R this condition will now be examined.
  • phasor groups 250 and 252 are repeated here as phasor groups 250 and 252, respectively, and the panned center signals have been added.
  • the front center signal, C is placed in the proportion 0.707C, andin-phase in the phasor 7 groups 250 and 252, appearing as phasors 254 and 256.
  • center-back channel C is divided in the proportion 0.707 in the left back and right back channels, and since these two phasors appear as a 0.707 fraction, the
  • centerback signal C is of an entirely different character than the center front signal C
  • the signal C having an out-ofphase relationship in the two channels will result in a vertical modulation of the groove 52 in FIG. 2, which is depicted by the arrow 248 inFIG. 9.
  • any signal recorded in this manner cannot be reproduced by a monophonic phonograph pick-up, nor by the monophonic section of an FM multiplex transmittingstation; consequently, when using the encoder of FIG. 8 the center-back location should preferably be used for occasional sounds such as reverberation, motion during planning, etc., and not for the placement of an important artist since he would not be heard when the signal is broadcast over AM radio or over monophonic FM radio.
  • Such signals would, however, be fully audible with stereophonic or quadruphonic modes of reproduction, and all other locations of the artist would be transmitted satisfactorily.
  • phasor groups 256 and 258 Another significant feature of the encoder is illustrated by the phasor groups 256 and 258 in FIG. 11, the former depicting the situation which results when the phasor groups 250 and 252 of FIG. 10 are added and the latter depicting the situation when the composite signal R (phasor group 252) is subtracted from L (phasor group 250).
  • L and R when L and R are added the phasors 1 L R, and R, all have an intensity equal to unity, whereas the front center signal C, is augmented by a factor 1.414, which is exactly what happens when a stereophonic record is played over a monophonic player.
  • the back center signal C,, is cancelled, however, because of the aforementioned out-of-phase relationship.
  • phasor groups 256 and 258 are extremely important since they indicate that if only a center front signal is present, i.e., no center back signal, the phasor group 256 will be greater than group 258, and, conversely, if there is only a center back signal but no center front signal,the phasor group 258 will be the larger. This interesting property is used toadvantage to enhance the operation of the decoder to be utilized with the encoder of FIG. 8, which will now be described.
  • the decoder illustrated in FIG. 12, is in many respects similar to the decoder of FIG. 6.
  • the signals L and R represented by phasor groups 238 and 240, respectively, are applied to respective input terminals 300 and 302, from whence they are applied in parallel to respective pairs of ill-networks 304, 306, 308 and 310. In this manner, each of the signals L and R passes without relative phase-shift through networks 304 and 308, respectively, and also pass with a relative phase-shift of through networks 306 and 310.
  • the individual phasors essentially identical with the corresponding phasors in groups 238 and 240, are differentiated with a prime to indicate that they have been subjected to the action of a lII-n6tWOIk and thus differ from the input phasors by an angle which is a ill-function of frequency, in addition to the differential angle introduced by the networks.
  • the outputs of networks 304 and 308 are applied directly to the input terminals of respective gain control amplifiers 3'12 and 314, the outputs of which are applied to respective loudspeakers 316 and 318.
  • the sig- 'nals applied to loudspeakers .316 and 318 contain predominant original signals L, and R,, respectively, the
  • Equal proportions, namely, 0.707, of the outputs of networks 306 and 308 are summed at a sum-' ming junction 320 to produce a composite signal consisting of a predominant signal L which is applied to a gain control amplifier 322 and thence to loudspeaker 324.
  • Equal negative portions, namely, 0.707, of the outputs of networks 304 and 310 are summed at a second summingnetwork 326 to produce for application to a fourth gain control amplifier 328 a composite signal composed of a dominant signal, R together with 0.707R, and 0.7071 after amplification, this composite signal is applied to loudspeaker 330.
  • phasor groups 332, 334, 336 and 338 which respectively portray the composite signals appearing at loudspeakers 316, 324, 330 and 318, that the predominant phasors at all four loudspeakers are in-phase.
  • the contaminating signals in each of the composite signals have little effect on the listening quality of the decoder as long as all of the predominant signals are simultaneously present because there is sufficient confusion and mixing in the air of sounds from different sources that the precise location of each sound is not easy to determine.
  • a logic and control circuit 340 which preferably is of the type disclosed in detail in -co-pending application Ser. No. l 18,271, the teaching of which is hereby incorporated by reference.
  • the logic described in this co-pending application is characterized as wave-matching logic which makes an instantaneous comparison of the waveshape of the signals and makes a decision to either increase the gain of amplifiers 312 and 314 which feed the two front loudspeakers 316 and 318 and diminishthe gain of the amplifiers which supply the back loudspeakers, or, conversely, whether to increase the gain of the back amplifiers 322 and 328 and reduce the gain of amplifiers 312 and 314.
  • the information on which the logic circuit bases its decisions is derived from the outputs of ill-networks 308 and 306 and is applied to input terminals 342 and 344, respectively.
  • the logic and control circuit 340 is operative to produce output signals at its output terminals 346 and 348 as follows: If a single channel signal L;, or two uncorrelated signals L; and Rare present in the input, the logic 340 produces output signals which are operative to increase the gain of amplifiers 312 and 314 and to decrease the gain of amplifiers 322 and 328. If, on the other hand, the principal signals are L 'alone, or uncorrelated signals L,, and R the logic is operative to produce signals which increase the gain of amplifiers 322 and 328 and to diminish the gain of amplifiers 312 and 314.
  • the decoder of FIG. 12 is given this additional capability by the provision of logic in addition to that provided by logic circuit 340.
  • the input signals L and R at input terminals 300 and 302 are applied via conductors 350 and 352, respectively, to a summing junction 354 and to a subtracting junction 356.
  • the sum signal appearing at the output of summing junction 354 being the sum of L and R is as depicted by phasor group 256 in FIG. 11, and the output of subtracting junction 356 is a composite signal having the properties portrayed by phasor group 258. It will be evident from reconsideration of FIG.
  • the outputs of junctions 354 and 356 are amplified in respectivequasilogarithmic amplifiers 358 and 360 and then rectified by respective rectifiers 362 and 364, which are preferably full-wave rectifiers, and integrated with leaky integrators 366 and 368, respectively.
  • the difference of the of outputs of the integrators, appearing at terminals 370 and 372, respectively, is proportional to the relative magnitudes of the sum and difference signals produced by junctions 354 and 356.
  • the former will be greater than the latter with the presence of a front-center signal.
  • a subtracting junction 372 which subtracts the signal at terminal 372 from the signal appearing at terminal 370.
  • the output of subtracting junction 372 is applied to a summing junction 374 where it is added to the output signal at "terminal 346 of logic and control circuit 340, the output of junction 374 being applied in parallel to the gain control electrodes of amplifiers 312 and 314 (which supply the front loudspeakers 316 and 318) to augment their gain.
  • a second subtracting junction 376 subtracts the signal appearing at terminal 370 from the signal appearing at terminal 372, which produces a negative output when a center-front signal is present; this is combined in a summing junction 378 with the output at terminal 348 of logic circuit 340, the sum signal serving to diminish the gainof amplifiers 322 and 328 which supply the rear loudspeakers 324 and 330, respectively. Conversely, if a center-back signal is present, the just-described logic would be operative to partially or completely turn off the front loudspeakers and to augment the gain of the rear loudspeakers.- g
  • the OR circuit takes the form of two pairs of rectifiers 380 and 382, and 384 and 386, so connected that one of the rectifiers in each pair is forward conducting and the other is backward connecting.
  • the signal appearing at terminal 346 is applied to rectifiers 380 and 382 and the output signal from summing junction 372 is applied to rectifiers 384 and 386.
  • the outputs of rectifiers 380 and 384 are added at points 388 and 392, and will be the greater of positive voltages at terminal 346 or at the output of junction 372.
  • the outputs of rectifiers 382 and 386 are combined at points 390 and 394 and will be the greater of negative voltages at terminal 346 or junction 372.
  • the voltages appearing at points 388 and 390 are added at summing junction 374; consequently, the output of summing junction374 will be the greater of the outputs of either the wavematching logic or the center front-center back control logic, and not the sum as in FIG. 12.
  • the negative voltage outputs at points 392 and 394 are added at summing junction 378, thereby producing the inverse of the output of junction 374.
  • the outputs of the junctions 374 and 378 are applied to the pairs of gain control amplifiers 312 and 314 and 322 and 328, respectively, as shown in FIG. 12.
  • the basic decoder of FIG. 12 is the same as that described in FIG. 6 with the single exception that the adding junction 326 inverts the phase of the R signal; alternatively, this phase reversal action may be obtained in the amplifier 328, or in its associated loudspeaker.
  • the composite input signals L and R may be shaped by frequency-dependent wave-shaping networks 380 and 382, respectively, before application to the logic circuitry so as to limit the action of the logic to voice signals, for example, or other instrumental sound, to make the logic less susceptible to erroneous decisions with certain high power, low frequency instruments, such as the bass drum.
  • the musical groups arranged in the front of a concert hall represented by the dashed-line enclosure 390, are designated by the dotted ellipses 400-412, the sounds produced by these groups being picked up by microphones 416-428, respectively.
  • the microphone circuits are isolated from each other by a plurality of buffer amplifiers 430-444, connected as shown.
  • Microphones 416, 418 and 420 are connected together and to the left front terminal 450, and microphones 424, 426 and 428 are likewise connected together and to the right front terminal 456.
  • the output of the center microphone 422, which may be reserved for the soloist, is fed in parallel to equal-gain amplifiers 436 and 438 so as to feed equal parts of the signal to the left front and right front terminals, thus constituting the center-front channel of the record.
  • Reverberation and other space effects may be conveniently picked up by a suitable arrangement of a dual cardioid microphone, exhibiting polar patterns depicted by 446 and 448, placed near the center of the hall to provide a realistic reverberation delay.
  • the outputs f the two transducers of the microphone are fed to terminals 452 and 454 which correspond to the back channels.
  • This arrangement of microphones produces two correlated signals: the sound produced by the soloist which is applied to the front channels 450 and 456, and that due to reverberation picked up by microphone sections 446 and 448 and applied directly and in-phase to the terminals 452 and 454. Since during the performance, the orchestra and the soloist will produce the stronger signals, the output of the summing junction 354 (FIG.
  • the time constants of the integrators 366 and 368 are preferably adjustable to permit adjustment to give a pleasing performance; attack times of about one to five milliseconds and decay times of the order of 0.4 seconds are typical.
  • Signal decoding apparatus for decoding first and second composite signals L and R respectively containing dominant signals L and R in phase with each other and each including two subdominant signal components L and R in quadrature relationship, with said L and R components in one of said composite signals leading and lagging, respectively, the L and R components in the other composite signal, and with one of the L and R, signals in phase with its respective associated R and L component and the other in phase opposition with the said associated component, said apparatus comprising, in combination:
  • decoder means including first and second input terminals to which said first and second composite signals are respectively applied and at least two allpass phase-shifting networks connected to respective ones of said input terminals, said phase-shifting networks being operative to shift the phase of one of said composite signals relative to the other by substantially thereby to position the L,, and R components in one of the relatively phase-shifted first and second composite signals either in phase coincidence or in phase opposition with corresponding components in the other relatively phaseshifted composite signal,
  • signal-combining networks for combining said relatively phase-shifted first and second composite signals to derive third and fourth composite signals respectively containing dominant signal components L and R, which are in phase with each other and each including two subdominant signal components L; and R and 17 means for applying composite signals respectively containing said signal components Lf, R L,, and R,, as predominant components to first, second, third and fourth signal amplitude-modifying means, respectively, for reproduction over four corresponding sound-reproducing devices; control circuit means operative in response to at least said relatively phase-shifted first and second composite signals to detect whether said relatively phase-shifted first and second composite signals contain substantially equal amplitude signal components in phase coincidence or in phase opposition and to produce a first control signal operative when applied to said first and second signal amplitude-modifying means to enhance the gain thereof when said first and second composite signals do not contain said signal components L,, and R;, either in phase or in phase opposition and to produce a second control signal operative when applied to said third and fourth signal amplitude-modifying means to enhance the gain thereof when said third and fourth composite signals do
  • a logic circuit connected to said first and second input terminals operative to compare the sum-and the difference of said first and second composite signals and to produce a third controlsignal when the sum exceeds the difference and to produce a fourth control signal when the difference exceeds I the sum, and
  • said combining means includes circuit means connected to said control circuit means and to said logic circuit and operative to select the larger of said first and said third control signals, and means for applying the larger of said control signals to said signal amplitude-modifying means.
  • Signal-decoding apparatus for decoding first and second composite signals L and R respectively containing dominant signals L, and R; in phase with each other and each including two subdominant signal components L and R in quadrature relationship, with the L,, and R components in one of said composite signals leading and lagging, respectively, the L,, and R components in the other of said composite signals, and with one of the L, and R signals in phase opposition with its respective associated R or L component and the other in phase with the said associated component, the apparatus including:
  • phase-shifting means operative to shift the phase of one of said composite signals relative to the other.
  • signal-combining networks for combining said relatively phase-shifted first and second composite signals to derive third and fourth composite signals respectively containing dominant signal components L and R, which are in phase with each other and each including two subdominant components L; and R g I first, second, third and fourth gain control means connected to receive composite signals respectivelycontaining said signal'components L,, R L,, and R, as predominant components;
  • control circuit operative in response to said relatively phase-shifted first and second composite signals to produce a first control signal operative when applied to said first and second gain control means to enhance the gain thereof when said first and second composite signals do not contain substantially equal signal components either in phase or in phase opposition and to produce a second control signal operative when applied to said third and fourth gain control means to enhance the gain thereof whenv said third and fourth composite signals do not contain substantially equal signal components either in phase or in phase opposition;
  • a logic circuit connected to receive and operative to compare the sum and the difference of said first and second composite signals and to produce a third control signal when the sum'exceeds the difference and to produce a fourth control signal when the difference exceeds the sum;
  • control circuit means for combining the control signals from said control circuit with thecontrol signals from said logic circuit for producing fifth and sixth control signals for application tothe said gain control means to control the gain thereof.
  • control circuit is operative to produce first and second control signals
  • logic circuit is operative to produce third or fourth control signals depending upon whether the sum exceeds the difference of the first and second composite signals, or vice versa
  • said combining means comprises means for adding the third and fourth control signals to the'first and second control signals, respectively.
  • said combining means includes a circuit connected to said control circuit and to said logiccircuit and operative to select the larger of the control signals produced by the control circuit and the logic circuit, and means for applying the larger of the signals to said gain control means.
  • Apparatus for reproducing on four soundreproducing devices four directional audio information signals respectively designated L R L,, and R contained in first and second composite signals respectively containing to the extent they are present dominant L, and R; component signals, and 'each including to the extent they are present sub-dominant L and R component signals, with said L and R component signals in one of said composite signals in substantially quadrature relationship with the corresponding component signals in the other of the composite signals, the combination comprising:
  • decoding circuit means including first and second pairs of all-pass phase-shifting networks connected to receive vsaid first and second composite signals, respectively, a first phase-shifting network of each pair being operative to shift the phase of the applied signal by a predetermined reference angle and a second phase-shifting network of each pair being operative to shift the phase of the applied signal by an angle differing from said reference angle by substantially 90,
  • signal-combining networks for combining the relatively phase-shifted first and second composite signals from the first phase-shifting network of one of said pairs and from the second phase-shifting network of the other of said pairs to derive third and fourth composite signals respectively containing dominant signal components L and R,, which are in phase with each other and each including two subdominant signal components L; and R signal-coupling means connected to receive and operative to couple composite signals respectively containing said signal components L;, R,, L and R as their predominant components to respective ones of first, second, third and fourth soundreproducing devices, said signal-coupling means including signal amplitude-modifying means for separately adjusting the amplitude of the composite signal applied thereto,
  • a control circuit operative in response to relatively phase-shifted first and second composite signals from the first phase-shifting network of one of said first and second pairs of phase-shifting networks and from the second'phase-shifting network of the other pair to produce a first control signal operative when applied to said first and second, signal amplitude-mo difying means to enhance the gain thereof when said first and second composite signals do not contain substantially equal signal components either in phase or in phase opposition or a second control signal operative when applied to said third and fourth signal amplitude-modifying means to enhance the gain thereof when said third and fourth composite signals do not contain substantially equal signal components either in phase or in phase opposition,
  • logic circuit connected to receive and operative to compare the sum and thedifference of the first and second composite signals and to produce at least one of third and fourth control signals depending upon whether the sum exceeds the difference, or vice versa, and
  • said last-mentioned means comprises means for adding the third and fourth control signals to the first and second control signals, respectively.
  • said last-mentioned means includes a circuit connected to said control circuit and to said logic circuit and operative to select the larger of the control signals produced by the control circuit and by the logic circuit, and
  • said logic circuit includes first and second summing junctions each connected to receive both of said first and second composite signals and operative to produce sum and difference signals, respectively,
  • first and second logarithmic amplifiers connected to receive and operative to amplify said sum and difference signals, respectively
  • third and fourth summing junctions each connected to receive both of said amplified sum and difference signals andoperative to produce at least one of said third and fourth control signals depending upon whether the sum of the first and second composite signals exceeds the difference of the first and second composite signals, or vice versa.
  • decoding circuit means connected to receive said first and second composite signals and operative in response thereto to derive third and fourth composite signals respectively containing predominant L and R component signals and each including sub-dominant L, and R, component signals,
  • first, second, third and fourth signal amplitudemodifying means respectively connected to receive and operative to couple said first, second, third and fourth composite signals to respective ones of first, second, third and fourth sound-reproducing means
  • a logic circuit connected to receive and operative to compare the sum and the difference of said first and second composite signals and to produce a first control signal when the sum exceeds the difference and to produce a second control signal when the difference exceeds the sum, and
  • said logic circuit includes first and second summing junctions to each of which both said first and second composite signals are applied and operative to produce sum and difference signals, respectively,
  • first and second logarithmic amplifiers connected to receive and operative to amplify said sum and difference signals, respectively

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  • Pure & Applied Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Acoustics & Sound (AREA)
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US00124135A 1971-03-15 1971-03-15 Apparatus for reproducing quadraphonic sound Expired - Lifetime US3821471A (en)

Priority Applications (11)

Application Number Priority Date Filing Date Title
US00124135A US3821471A (en) 1971-03-15 1971-03-15 Apparatus for reproducing quadraphonic sound
CA133,379A CA978860A (en) 1971-03-15 1972-01-28 Apparatus for recording and reproducing quadruphonic sound
GB841272A GB1387874A (en) 1971-03-15 1972-02-23 Apparatus for recording and reproducing quadraphonic sound
DE2209424A DE2209424C3 (de) 1971-03-15 1972-02-28 Codiermatrix zur Codierung von vier Signalen in zwei Signalgemische
NL7203169A NL7203169A (de) 1971-03-15 1972-03-09
JP47024794A JPS5110962B2 (de) 1971-03-15 1972-03-13
FR7209094A FR2130306B2 (de) 1971-03-15 1972-03-15
BE780710A BE780710R (fr) 1971-03-15 1972-03-15 Systeme d'enregistrement et de reproduction
FR7209093A FR2130305B2 (de) 1971-03-15 1972-03-15
BE780711A BE780711R (fr) 1971-03-15 1972-03-15 Decodeur pour systeme de reproduction
JP8911275A JPS5316281B2 (de) 1971-03-15 1975-07-21

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US00124135A US3821471A (en) 1971-03-15 1971-03-15 Apparatus for reproducing quadraphonic sound

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US3821471A true US3821471A (en) 1974-06-28

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JP (2) JPS5110962B2 (de)
BE (2) BE780711R (de)
CA (1) CA978860A (de)
DE (1) DE2209424C3 (de)
FR (2) FR2130305B2 (de)
GB (1) GB1387874A (de)
NL (1) NL7203169A (de)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3919480A (en) * 1973-11-29 1975-11-11 Sony Corp Decoding apparatus for reproducing four separate information signals
US3937885A (en) * 1974-09-06 1976-02-10 Motorola, Inc. Control circuit for a matrixed four channel audio reproducing system
US3944735A (en) * 1974-03-25 1976-03-16 John C. Bogue Directional enhancement system for quadraphonic decoders
US3983334A (en) * 1974-02-26 1976-09-28 Victor Company Of Japan, Limited Matrix and equalizer circuit with gain control
US4018992A (en) * 1975-09-25 1977-04-19 Clifford H. Moulton Decoder for quadraphonic playback
US4081606A (en) * 1975-11-13 1978-03-28 National Research Development Corporation Sound reproduction systems with augmentation of image definition in a selected direction
DE3607610A1 (de) * 1985-03-07 1986-09-18 Dolby Laboratories Licensing Corp., San Francisco, Calif. Decoder
US5046098A (en) * 1985-03-07 1991-09-03 Dolby Laboratories Licensing Corporation Variable matrix decoder with three output channels
US20040213421A1 (en) * 2003-04-24 2004-10-28 Jacobs Stephen M. Volume control in movie theaters
US20070218109A1 (en) * 2004-06-28 2007-09-20 Ajinomoto Co. Inc Nutrient composition and composition for prevention/mitigation of digestive tract depression
US20080019533A1 (en) * 2006-07-21 2008-01-24 Sony Corporation Audio signal processing apparatus, audio signal processing method, and program
US11039263B2 (en) * 2019-05-29 2021-06-15 Mark Petrouske Wide effect sound producing method

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5827645B2 (ja) * 1977-11-24 1983-06-10 株式会社日立製作所 静止誘導機器
US4941177A (en) * 1985-03-07 1990-07-10 Dolby Laboratories Licensing Corporation Variable matrix decoder

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3919480A (en) * 1973-11-29 1975-11-11 Sony Corp Decoding apparatus for reproducing four separate information signals
US3983334A (en) * 1974-02-26 1976-09-28 Victor Company Of Japan, Limited Matrix and equalizer circuit with gain control
US3944735A (en) * 1974-03-25 1976-03-16 John C. Bogue Directional enhancement system for quadraphonic decoders
US3937885A (en) * 1974-09-06 1976-02-10 Motorola, Inc. Control circuit for a matrixed four channel audio reproducing system
US4018992A (en) * 1975-09-25 1977-04-19 Clifford H. Moulton Decoder for quadraphonic playback
US4081606A (en) * 1975-11-13 1978-03-28 National Research Development Corporation Sound reproduction systems with augmentation of image definition in a selected direction
DE3607610A1 (de) * 1985-03-07 1986-09-18 Dolby Laboratories Licensing Corp., San Francisco, Calif. Decoder
US4799260A (en) * 1985-03-07 1989-01-17 Dolby Laboratories Licensing Corporation Variable matrix decoder
US5046098A (en) * 1985-03-07 1991-09-03 Dolby Laboratories Licensing Corporation Variable matrix decoder with three output channels
US7251337B2 (en) * 2003-04-24 2007-07-31 Dolby Laboratories Licensing Corporation Volume control in movie theaters
US20040213421A1 (en) * 2003-04-24 2004-10-28 Jacobs Stephen M. Volume control in movie theaters
USRE43132E1 (en) * 2003-04-24 2012-01-24 Dolby Laboratories Licensing Corporation Volume control for audio signals
USRE44261E1 (en) * 2003-04-24 2013-06-04 Dolby Laboratories Licensing Corporation Volume control for audio signals
USRE44929E1 (en) 2003-04-24 2014-06-03 Dolby Laboratories Licensing Corporation Volume control for audio signals
USRE45389E1 (en) * 2003-04-24 2015-02-24 Dolby Laboratories Licensing Corporation Volume control for audio signals
USRE45569E1 (en) * 2003-04-24 2015-06-16 Dolby Laboratories Licensing Corporation Volume control for audio signals
US20070218109A1 (en) * 2004-06-28 2007-09-20 Ajinomoto Co. Inc Nutrient composition and composition for prevention/mitigation of digestive tract depression
US7993668B2 (en) * 2004-06-28 2011-08-09 Ajinomoto Co., Inc. Nutrient composition and composition for prevention/mitigation of digestive tract depression
US20080019533A1 (en) * 2006-07-21 2008-01-24 Sony Corporation Audio signal processing apparatus, audio signal processing method, and program
US8160259B2 (en) * 2006-07-21 2012-04-17 Sony Corporation Audio signal processing apparatus, audio signal processing method, and program
US11039263B2 (en) * 2019-05-29 2021-06-15 Mark Petrouske Wide effect sound producing method

Also Published As

Publication number Publication date
GB1387874A (en) 1975-03-19
JPS5316281B2 (de) 1978-05-31
FR2130305B2 (de) 1979-04-27
FR2130306B2 (de) 1977-12-23
DE2209424A1 (de) 1972-09-28
FR2130305A2 (de) 1972-11-03
NL7203169A (de) 1972-09-19
BE780711R (fr) 1972-09-15
BE780710R (fr) 1972-09-15
DE2209424C3 (de) 1978-09-28
DE2209424B2 (de) 1978-01-26
FR2130306A2 (de) 1972-11-03
JPS5110962B2 (de) 1976-04-08
CA978860A (en) 1975-12-02
JPS5136903A (de) 1976-03-29
JPS4849401A (de) 1973-07-12

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