Umted States Patent
`
`[19]
`
`[11] Patent Number:
`
`5,666,422
`
`Harrison et al.
`
`[45] Date of Patent:
`
`Sep. 9, 1997
`
`USOO5666422A
`
`[54] REMOTE SPEAKER FOR
`sURR()UN[)-s()UN]) AppL1CA'1‘1()Ns—
`
`[76]
`
`Inventors: Robert W. Harrison, 18 Westfield
`Park’ Cortland’
`Alan
`Whitney, 227 Prospect Hfll Rd.,
`Horseheads’ NY. 14845
`
`[211 APP1-N0-12459674
`~
`9
`[22]
`Ffled_
`May 18 1994
`
`....... H04R 5/00
`Int. C15’
`[51]
`
`[52] U.S. Cl. ................................... 381/18; 381/24; 381/1;
`381/28
`12352;’ 112%
`’
`’
`’
`
`[58] Field of Scare;
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`’
`
`’
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`’
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`‘
`
`4,394,535
`4,612,663
`4,819,269
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`'
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`7/1983 Bingham ................................. .. 381/17
`9/1986 Holbrook et a1.
`.
`7
`4/1989 Klayman .
`
`4a399v33§_
`5,02’/,68I
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`,
`
`,
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`2/1990 M]°dZ‘k°W5k1 e‘ 31-
`-
`
`Iwamatsu ................................ ..
`"
`Hon. """"""
`Haruson ....................................
`FOREIGN PATENT DOCUMENTS
`
`Japan ....................................... 331/24
`4/1988
`0076699
`Japan ....................................... 381/19
`5276600 10/1993
`Primary Examiner—Minsun Oh
`.
`.
`A”°'"ey’ Agem’ °’ Fm“ Bmmd’ Bwwn & Mlchaels
`[57]
`ABSTRACT
`A surround-sound systemforuse with conventional TV sets,
`using a wireless remote bipolar rear speaker (or two con-
`ventional speakers fed out of phase) for the surround
`(difierence) channels. The use of the rear speaker(s) and the
`mono (left plus right) front speaker on the TV set creates
`“ hantom” left and right front speakers and allows full
`.
`.
`.
`’
`suzI'onnd,sound_ wrthout mod1ficat1on to the TV set or
`addJ.tl0Il3.1. 3IDp]J.fiCI'S 01' SP€3.kCl'S.
`
`12 Claims, 3 Drawing Sheets ~
`
`’
`Cot d
`Ref
`1 e
`erences
`U.S. PATENT DOCUMENTS
`.
`3,069,505 12/1962 Oollms et a1.
`............................ 381/14
`11,1969 Sorkm.
`3,478,167
`Hafler _
`4/1973 Iida .
`9/1973 Ito et al.
`
`56
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`[
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`]
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`.
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`3,725,586
`3,757,047
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`.
`
` 1
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`APPLE 1014
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`APPLE 1014
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`1
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`U.S. PatentUS. Patent
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`Sep. 9, 1997Sep. 9, 1997
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`Fig. 1Fig. 1
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`U.S. Patent
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`Sep. 9, 1997
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`Sheet 2 of 3
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`Fig. 3
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`In
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`Carr. C‘/urrent
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`Sheet 3 of 3Sheet 3 of 3
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`U.S. PatentUS. Patent
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`Sep. 9, 1997Sep. 9, 1997
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`1
`REMOTE SPEAKER FOR
`SURROUND-SOUND APPLICATIONS
`
`FIELD OF THE INVENTION
`
`The invention pertains to the field of surround sound
`apparatus. More particularly, the invention pertains to si.rmr-
`lated quadraphonic systems applicable to television home
`theater or the like.
`
`BACKGROUND OF THE INVENTION
`
`In the average movie theater, two types of “surround”
`systems are used—the 70 mm 6—track magnetic system, and
`the more common 35mm optical arrangement. The former
`uses a magnetic strip attached to the film to supply six
`discrete channels, and the latter uses two optical audio
`tracks. This two-channel system is the basis for home
`surround sound decoders.
`
`Every stereo videodisc, tape and MTS broadcast that was
`surround encoded still contains the same rear channel infor-
`mation as the two—channe1 magnetic master from which the
`theatrical 35mm optical soundtrack was produced. In other
`words, your stereo videotape or disc of Star Trek I, II, III,
`Raiders of the Lost Ark, Superman and Star Wars can be
`decoded to produce surround sound at home. In addition,
`LPs, CDs and any stereo audio material can benefit from
`surround sound decoding. Ambiance extraction is a pleasant
`side effect that many decoders provide. In a nutshell, if the
`recording was made in a large hall, or a small club, “sur-
`round sound” will reproduce the recording environment
`faithfully.
`Assuming the listener is seated centered between the two
`speakers, sound which is recorded “in phase” and with equal
`amplitude in each channel in a standard stereo system will
`appear to the listener to be located equidistant between the
`two speakers, as the two in-phase audio signals add together.
`The sound can be shifted left-to-fight by varying the ratio of
`the amplitude of the left and right signals.
`the
`By subtracting the left and fight signals (L-R),
`in-phase signals will be cancelled, and the out-of-phase
`signals are recovered. This is the basis of the “matrix
`encoding” which is used to record surround information
`which is inaudible to listeners with conventional stereo
`equipment.
`If a signal is recorded at equal amplitude on each channel
`of the stereo but 180° out of phase, an exactly centered
`listener would ideally hear nothing. as the two signals cancel
`each other out. As a practical matter, the signals are audible,
`but sound odd—flrere is almost no centered sound at all, but
`the source appears to shift past the left or right speaker to be
`“out there somewhere”. This accounts for the occasional
`feeling when playing a surround-encoded movie on conven-
`tional two-speaker stereo equipment that the sound is com-
`ing from behind or off to one side or the other.
`In a conventional surround system there are four or five
`speakers. The standard left and right speakers of the normal
`stereo sound are located in front of the viewer to the left and
`right of the screen. The left and right rear (surround) signals
`are reproduced on speakers behind the listener. Many sys-
`tems will also add a center (Left plus Right, or the same as
`monophonic) signal in front, under the screen,
`to add
`“centering” for dialog.
`In recent years there have been two conflicting trends in
`more-expensive television equipment. First, it has become
`increasingly common to include stereo decoders in
`televisions, which in turn requires two speakers for sound
`
`2
`reproduction. Second. the portion of the front of the TV
`which is occupied by the screen has become larger, until
`there is no room left for even one speaker, let alone two. As
`a result, although mono TV sets may still have a front-facing
`speaker (albeit small), the speakers in most stereo TVs have
`been moved to the sides of the cabinet, usually pointing
`outward. These closely spaced speakers provide little stereo
`effect,’ at best. At the same time, it has become more
`common than ever to place the TV into an “entertainment
`center” or bookcase, which surrounds the TV set and blocks
`the speakers. This results in a loss of whatever stereo effect
`there might have been.
`As a result, many consumers have abandoned the sound
`system in their TV sets completely, using an external ampli-
`fier and speakers (in most cases an existing stereo setup)
`driven by the stereo output from the TV (if present), or from
`a VCR to drive two front speakers. This adds considerable
`expense to the cost of the television, not to mention the need
`for space for the two additional front speakers. These
`speakers often cannot be placed too close to the TV because
`of magnetic effects, and the need to center the TV between
`them for proper stereo effect restricts the placement of all of
`the components in the room.
`As “surround encoded” videotapes and television trans-
`missions have become more common in recent years there
`has been an influx of surround decoders on the market
`Typical of these are the various Dolby® systems, or the
`Dynaco model QD-1, which is a version of the decoder
`described in a 1970 Audio Magazine article by David Hailer
`for use with the then-emerging quadraphonic sound tech-
`nology (which has since been abandoned). Hafler’s U.S. Pat.
`No. 3,697,692 is essentially the same as the Dynaco QD-1.
`These systems require, at a minimum, a stereo amplifier
`(QD-1) or two (all low—level systems such as Dolby, THX,
`or the system described in co-pending application Ser. No.
`08/184,648) and four or five separate speakers, with asso-
`ciated wiring and cables. The expense can be quite high and
`setting up such a system is not trivial, especially for the
`average non—technical consumer.
`Several patents have suggested the use of three speakers
`for stereo setups. For example. see Sorkin, U.S. Pat. No.
`3,478,167, or Klayman, U.S. Pat. No. 4,819,269. Neither of
`these are concerned with surround sound applications, but
`simply show three-speaker stereo arrangements using dif-
`ference signals as part of the array of speakers.
`Remote wireless speakers for audio applications have
`been known for some time. For example, see Mlodzikowski,
`et. al., U.S. Pat. No. -4,899,388, which uses an infrared
`transmitter to drive two remote battery powered speakers for
`a conventional stereo system. For many years General
`Electric sold a wired-wireless (carrier current) monophonic
`remote speaker under the “Porta-Fi” trademark, and Radio
`Shack also sold a similar wireless stereo remote speaker
`system around 1990. Accessory-maker Recoton’s Model
`W100 wireless stereo speaker system also transmitted
`through the house AC wiring, and their newest wireless
`speakers use a 900 MHz radio transmitter/receiver setup.
`Headphone manufacturer Koss has a pair of “Kord.lesspeak-
`ers” which receive audio signals via an infrared transmitter.
`Bipolar speakers have been used in surround systems
`before, but arranged on the sides of the listening area
`pointing front and rear, or in front pointing front and rear.
`SUMMARY OF THE INVENTION
`
`The invention provides a surround-sound system for use
`with conventional I V sets, using a wireless remote bipolar
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`3
`rear speaker (or two conventional speakers fed out of phase)
`for the surround (dilference) channels. The use of the rear
`speaker(s) and the mono (left plus right) front speaker on the
`TV set creates “phantom” left and right front speakers, and
`allows full surround sound without modification to the TV
`
`set or additional amplifiers or speakers.
`BRIEF DESCRIPTION OF THE DRAWING
`
`FIG. 1 shows a View of the preferred embodiment of the
`invention, using IR transmission and a bipolar speaker.
`FIG. 2 shows an alternate embodiment of the invention.
`using RF transmission and a pair of conventional speakers.
`FIG. 3 shows a block diagram of the preferred embodi-
`ment of the invention. using IR transmission and a bipolar
`speaker.
`FIG. 4 shows a block diagram of an alternate embodiment
`of the invention, using RF transmission and a bipolar
`speaker.
`FIG. 5 shows a block diagram of an alternate embodiment
`of the invention. using carrier current transmission and a pair
`of conventional speakers.
`FIG. 6 shows an alternate embodiment of the invention. as
`used in a projection television setup.
`
`DESCRIPTION OF THE P D
`EIVIBODIMENT
`
`The invention comprises a remote speaker system for use
`with television sets or other components, providing a
`surround-sound effect which can be easily added to an
`existing system without great expense or complexity. The
`system components are a transmitter unit (FIG. 1 and 2. (1))
`and a receiver unit with speaker(s) (FIG. 1. (8)—(9); FIG. 2,
`(13)-(15))
`FIG. 1 shows the arrangement of the preferred embodi-
`ment of the invention in use. The listener (7) sits facing the
`TV set (1) which has a built-in speaker (4) which provides
`the monaural (Left plus Right (L+R)) audio of the TV signal.
`While the invention will be described in the context of an
`add-on accessory for use with an existing conventional
`mono TV set. it will be understood by one skilled in the art
`that it may be used with a stereo TV or home theater system,
`or built-in to a television at the factory.
`On the television set (1) is the transmitter unit (2) of the
`invention, shown in FIG. 1 in an embodiment having an
`infrared (IR) diode (3) for transmitting the sound informa-
`tion. The transmitter unit (1) decodes the rear surround
`information (dilferenoe information) from the TV signal
`stereo sound or other audio information. As will be seen in
`the discussions of FIGS. 3-5, below, the audio input can be
`supplied to the transmitter unit, and transmitted to the
`remote unit, in a number of ways.
`The transmitter unit (1) in FIG. 1 transmits the difference
`sound information, which is a single monaural signal (L—R
`or R—L), via the IR transmitter diode (3) to the IR detector
`(11) on the remote speaker amplifier/receiver unit (8), which
`is located behind the listener (7). The preferred embodiment
`of the invention uses a bipolar speaker (9) in which a single
`coil drives a cone which is open on both sides. When fed by
`the (L—R) difference signal, the bipolar speaker (9) auto-
`matically generates (L—R) from the front of the speaker and
`(R—L) from the back. The bipolar speaker (9) is set up so the
`sound is directed to both sides. with the (L—R) front of the
`speaker (if fed by (L—R) signal) directed to the left.
`The provision of the difference signals (L—R) and (R-L)
`behind the listener and the sum signal (L+R) at the TV
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`centered in front of the listener creates the auditory illusion
`that there are Right and Left front speakers, or “phantom
`speakers” (shown as dotted speakers (5) and (6)). Thus.
`conventional stereo (non-surround encoded) signals appear
`to come from the “phantom” speakers correctly located to
`theright and left of the screen. If the signal is encoded with
`out-of-phase S1l1‘1'OllIld information. it is correctly decoded
`and appears in correct relation to the real center speaker and
`phantom left and right front speakers. Thus, through the use
`of a single bipolar remote rear speaker and a conventional
`TV front speaker the user has a true “surround sound” setup
`as if he/she had the full 5 speakers normally used.
`FIG. 2 shows an alternate embodiment of the invention.
`
`The IR transmission of FIG. 1 is replaced by a transmitter
`(12) and receiver (16) linked by a radio frequency (RF)
`transmission system (17), and the bipolar speaker (9) is
`replaced by two conventional speakers (13) and (15) driven
`by an arnplifier/remote unit (14). Alternatively,
`the
`amplifier/remote unit (14) could be built into the cabinet of
`one of the two speakers.
`FIG. 6 shows still another alternate embodiment of the
`invention. as it might be used in connection with large screen
`projection televisions in a “home theater” environment. The
`TV projector (65) is a conventional unit, housing the
`receiver and video projection components. The screen (68)
`is placed at a distance from the projector (65). A front
`speaker (69) connected to the projector (65) by a cable (67)
`is preferably placed behind the screen (68) for maximum
`centering of the front sound Alternatively, the front speaker
`(69) could be mounted above or below the screen. This is all
`conventional to projection type television sets.
`The remote speakers of the invention can be easily added
`to the projection TV home theater. The transmitter unit can
`be placed on top of the projector, if an aftermarket system,
`or it can be built into the projector (65) as shown in FIG. 6.
`If an RF embodiment of the invention is desired, the antenna
`(66) could protrude from the top of the projector (65). The
`remote speakers (60) and (61) would be placed behind the
`listening area, preferably hung from the wall. The receiver
`unit is shown built into speaker (60) with its antenna (62)
`extending above or below the speaker as desired. The
`speakers are connected by a wire (63).
`FIGS. 3 through 5 show block diagrams of alternate
`embodiments of the invention, having variations in audio
`signal source, transmission method, and remote speaker
`types. It will be understood by one sldlled in the art that the
`method of audio derivation or transmission and speaker
`choice are independent of each other, and can be mixed as
`required by the dictates of the application.
`Power supplies are not shown in FIGS. 3-5, as they will
`be understood to be completely conventional, and will
`depend on the exact circuitry chosen and economic consid-
`erations. Such commonly used power supply elements as the
`familiar “brick" transformer unit which plugs into an AC
`outlet and provides low AC or DC voltage for calculators,
`answering machines, etc., would be suitable for this appli-
`cation.
`FIG. 3 shows an embodiment of the invention as shown
`in FIG. 1, using IR transmission and a bipolar speaker.
`Starting at the left, the TV signal source is shown at (46).
`This can be any source of audio/video signal. such as an
`antenna, CATV cable or cable converter box, or a VCR,
`which connects to the antenna terminals of the TV set (31).
`The transmitter unit is shown by dotted fines (34). In this
`embodiment the input is supplied by an inductive pickup
`(32) and intermediate frequency (IF) detector unit (35). This
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`arrangement is commercially available as the “F.R.E.D." TV
`stereo decoder, manufactured by Recoton Corporation. The
`operation is based upon the fact that for economic reasons
`mostTV set tuners convert the incoming signal of whatever
`channel to the same IF frequency, which allows the use of
`standardized components for all circuitry following the
`tuner. This IF signal will leak from the TV set to some
`extent, and can be picked up and detected by suitable
`circuitry.
`The detected audio is fed into a stereo decoder (36) in
`order to extract the Left and Right channel signals. This is
`a standard circuit, which can use any of the commercially
`available stereo decoder “chips” and associated circuitry.
`The diiference signal (L—R or R-L) must now be gener-
`ated from the Left and Right signals. There have been many
`active circuits patented which can accomplish this (see, for
`example, Holbrook, U.S. Pat. No. 4,612,663, Ito, et. al.
`(Sansui), U.S. Pat. No. 3,757,047, or Iida (Sony), U.S. Pat.
`No. 3,725,586), but the preferred embodiment uses the
`simple transformer-based low level decoder circuit disclosed
`in co—inventor I-Iarrison’s copending application Ser No.
`08/184,648, shown at (37).
`The transformer (37) can be any audio type having
`suitable impedance characteristics for the application. For
`the typical situation with current
`technology audio
`equipment, it would be recognized by one skilled in the art
`that input impedances in excess of IKQ, and outputs at or
`below 1K.Q would be appropriate. Other applications, or
`changes in standards in the future, might require other
`impedance rages, which would be within the ability of one
`skilled in the art to select. Such a transformer may be
`purchased from Triad, selected from series SP, which is a
`series of small transformers, specifically model SP-21.
`Since low bass sounds are essentially non-directional,
`there is no need to pass these frequencies through to the
`surround channels. Therefore, the preferred transformer has
`frequency characteristics which are fiat above 300Hz, and
`which roll off —3dB at 200Hz, and essentially cut off
`flequencies below 100Hz.
`The right and left channels of the stereo signal having the
`out-of-phase surround information is supplied to the primary
`of the transformer at the end connections. The center tap of
`the secondary is grounded, and the difference signal is taken
`from one of the end connections of the secondary.
`This difference signal is used as input to an infrared (IR)
`driver (38) which modulates an IR laser diode (39) to
`transmit the difference signal. The IR driver circuit can be
`any conventional circuit, as is commonly used in the art,
`such as in the Koss “Kordlesspeakers”, or in Mlodzikowski,
`et. al., U.S. Pat. No. 4,899,388, cited above.
`Turning now to the receiver unit (40), an IR detector
`circuit (41) using a detector diode (41) in conventional
`fashion as used in the above-cited units, detects the diifer—
`ence audio signal from the IR signal. This signal is amplified
`in an amplifier circuit (43). which can be any commonly
`available audio amplifier circuit as may be determined by
`the designer. The power capability of the amplifier does not
`need to be very large—the surround channels typically need
`only be about half as powerful as the main (TV set)
`amplifier.
`The amplifier drives a bipolar speaker (44) to produce the
`surround sound. The bipolar speaker can be any commer-
`cially available bipolar speaker of suflicient capacity to
`handle the power output of the amplifier, such as the model
`C10T70 driver in a model 510 cabinet from Sondolier.
`FIG. 4 shows an alternative embodiment of the invention
`showing an alternate audio source and a different transmis-
`
`sion method from FIG. 5. The TV program source (46) is
`used as input to a VCR (51) having a tuner capable of
`decoding the MTS stereo, and/or which can play stereo
`surround encoded videotapes. The VCR (51) then drives the
`TV set (31) in any conventional way. The left (52) and fight
`(53) audio outputs from the VCR are used as the inputs to
`the difference signal decoder circuit (37), as described above
`for FIG. 3.
`
`The decoded difference signal (L—R) becomes the audio
`input to a radio transmitter (48) driving antenna (47). The
`transmitter is preferably an FM transmitter operating under
`the license-free “part 15” provisions, such as the ones used
`in “wireless mic” systems. The transmitter could be one
`operating on the FM broadcast band, such as used in Radio
`Shack Model 33-1076 or many commonly available kits and
`modules. This would allow the mating receiver (50) to be a
`simple FM broadcast receiver. Alternatively, the transmitter
`(48) could be on another band, such as the 170 MHZ system
`used by Radio Shack model 32-1224 wireless microphones,
`or the 902-928 MHz system used by the Recoton remote
`speakers.
`The receiver unit (40) comprises an antenna (49) and
`matching FM receiver (50) to the transmitter (48), which
`drives audio amplifier (43) and speaker (44) as shown in
`FIG. 3.
`
`Still another embodiment using another audio source
`system, transmission system, and speaker arrangement is
`shown in FIG. 5. In many cases the input to the home
`television system (46) is a single channel source such as the
`output of a cable box, laser disk player or VCR, usually on
`channel 3 or 4. It is possible, then, to provide the system of
`the invention with a single channel TV tuner (52) connected
`in parallel to the TV (31) antenna input by a “T” (50), which
`can drive any commercially available stereo decoder (36)
`driving the difference decoder (37), as noted in the discus-
`sion of FIG. 3. This would allow the invention to be used
`with most home TV and VCR systems without any modi-
`fication to the TV and without any need for either the VCR
`orTV set to be MTS stereo capable. The remote rear speaker
`would automatically follow the same program as the TV set
`when the channel is selected on the cable box or VCR.
`Alternatively, at somewhat greater expense and increase in
`complexity of use, the tuner (52) could be fully tunable for
`use with systems without the fixed channel converter.
`The difference signal output becomes the input to a ‘Wired
`wireless” or “carrier current” transmitter (59). “Wired wire-
`less” is used by many intercom systems, the BSR X-10
`wireless remote control systems, and, in the stereo field, the
`GE Porta-fi remote speakers, as well as the Recoton and
`Radio Shack units. The signal to be transmitted is imposed
`upon a low-frequency (zl00KHz) RF signal, and the carrier
`is coupled (60) to the AC power line, usually using the same
`power cord as provides the power to run the unit. An
`appropriate receiver unit (55) can receive the signal by being
`plugged into any outlet (53) within the same general area.
`The receiver unit (40) shown in FIG. 5 is essentially the
`same as the GE Porta-fi monophonic remote speaker unit,
`except that instead of a single speaker, two (56) and (57) are
`provided fed out of phase by crossing the speaker wires (58)
`between the speakers. A carrier current receiver (55) is
`coupled (54) to the AC line (53), detecting the audio on the
`RF carrier, and driving a conventional audio amp (43). as in
`the embodiments of FIGS. 3 and 4.
`
`Although all of the embodiments shown have been
`described in terms of television surround sound, it will be
`understood by one skilled in the art that many stereo sources
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`such as Compact Disks or FM signals may benefit from
`surround speakers as well.
`Accordingly, it is to be understood that the embodiments
`of the invention herein described are merely illustrative of
`the application of the principles of the invention. Reference
`herein to details of the illustrated embodiments are not
`intended to limit the scope of the claims. which themselves
`recite those features regarded as essential to the invention.
`I claim:
`1. A remote wireless surround sound speaker for use with
`audio sources having left and right audio signals, compris-
`mg:
`
`a) a diflerence signal transmitter unit comprising decoder
`means for generating a difference signal representing
`the diflerence between the right and left audio signals
`and transmitter means for transmitting the diiference
`signal to a remote location, wherein the decoder means
`of the difference signal transmitter unit is a transformer
`having a primary winding having inputs at each end of
`the winding and a secondary winding having an output
`at one end of the winding and a grounded center tap,
`wherein the left and right audio signals are connected
`to the inputs at the ends of the primary winding, and the
`dilference signal is output from the output at the end of
`the secondary winding. and
`b) a remote receiver unit comprising
`i) receiver means for receiving and detecting the dif-
`ference signal transmitted by the difference signal
`transmitter unit. having an input for accepting the
`signal from the transmitter unit. and a diiference
`signal output comprising the received audio di.fier-
`ence signal.
`ii) amplifier means for amplifying an audio signal,
`having an input connected to the dilference signal
`output of the receiver means. and an output for
`driving speakers with the difference signal, and
`iii) speaker means connected to the output of the
`amplifier means, such that the speaker means repro-
`duces a signal representing the diiference between
`the left and right audio signals of the audio source.
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`2. The remote wireless surround sound speaker of claim
`1, in which the audio source is the audio portion of a
`television signal.
`3. The remote wireless surround sound speaker of claim
`2, in which the audio source is generated by an IF receiver
`means for receiving leaked IF signals from a TV set and
`decoding the left and right audio signals from the leaked IF
`signals.
`4. The remote wireless surround sound speaker of claim
`2. in which the audio source is generated by a television
`tuner.
`
`5. The remote wireless surround sound speaker of claim
`2, in which the audio source is generated by a playback
`means for playing recorded television signals.
`6. The remote wireless surround sound speaker of claim
`5. in which the playback means is a VCR.
`7. The remote wireless surround sound speaker of claim
`5, in which the playback means is a laserdisc player.
`8. The remote wireless surround sound speaker of claim
`1, in which the transmitter means of the transmitter unit
`transmits an infrared signal. and the receiver means of the
`remote receiver unit receives the infrared signal transmitted
`by the transmitter unit.
`_
`9. The remote wireless surround sound speaker of claim
`1, in which the transmitter means of the transmitter unit
`transmits aradio frequency signal, and the receiver means of
`the remote receiver unit receives the radio frequency signal
`transmitted by the transmitter unit.
`10. The remote wireless surround sound speaker of claim
`1, in which the transmitter means of the transmitter unit
`transmits a low-frequency radio signal coupled to an AC
`power line, and the receiver means of the remote receiver
`unit receives the low-frequency radio signal transmitted by
`the transmitter unit from the AC power line.
`11. The remote wireless surround sound speaker of claim
`1, in which the speaker means of the remote receiver unit is
`a bipolar speaker.
`12. The remote wireless surround sound speaker of claim
`1, in which the speaker means of the remote receiver unit is
`a pair of speakers conneaed out of phase relative to each
`other.
`
`8
`
`