Abstract: A compatible four channel system primarily for use in conjunction with a radio transmission system for transmitting four individual audio signals over a medium having primary and secondary information channels and first and second auxiliary information channels, the primary and secondary channels carrying information that is consistent and compatible with existing monophonic and stereo-phonic standards.

Abstract: A system including a compact array of microphones in combination with signal combining circuitry, especially suited for use with surround-sound sources, for producing two composite signals LT and RT corresponding to those required by an SQ-matrix-type quadraphonic system to establish the directional position of the sound sources. The signals produced by selected ones of the microphones are combined to produce an auxiliary signal which contains, to the extent they are present, equal proportions of signals corresponding to the signals LF, RF, LB and RB of the SQ quadraphonic system which exhibit an equal angular relationship respecting corresponding signals in a composite signal representing the sum of LT and RT. The auxiliary signal enables decoding of the directional signals in the 4-3-4 or the .theta.-3-4 modes.

Abstract: A magnetic phonograph pick-up cartridge having a fixed assembly portion and a replaceable assembly portion wherein the replaceable portion includes self-contained, longitudinally-extending stylus pole pieces surrounding a pivotally mounted stylus magnet. One end portion of the magnet has a stylus-containing shank connected so that movement of the stylus by a phonograph record groove will cause a related pivotal movement of the magnet. The stylus pole pieces, which could include one or two pole piece pairs, are positioned to define a longitudinally extending pole gap. The magnet has a longitudinal dimension less than that of the pole pieces and is positioned within the pole gap. A resilient collar is attached to the stylus pole pieces and is used to pivotally mount the magnet so that movements of the stylus will alter the magnetic flux coupled from the magnet to the stylus pole pieces.

Abstract: A system including a compact array of microphones and signal-combining circuitry, especially suited for use with surround-sound sources, for producing two composite output signals corresponding to those required by a matrix-type quadraphonic system to establish the directional position of the sources. The outut signals from one embodiment of the system can be used directly to record an SQ-matrixed tape, or they can be applied to a disc cutter to produce an SQ record, and in another embodiment the output signals can be used directly to record a "regular matrix" (RM) tape or they can be applied to a disc cutter to produce an "RM" record. Thus, the disclosed systems perform the function of the conventional multi-microphone and encoding system for SQ or RM recording or broadcasting.

Abstract: A system including a compact array of special purpose microphones and an encoder, especially suited for use with surround-sound sources, for producing two composite output signals equivalent to those required by the "SQ" quadraphonic system to establish the directional position of the sources. The output signals from the system can be used directly to record an "SQ"-matrixed tape, or they can be applied to a disc cutter to produce an "SQ" record, or they can be broadcast for reception by FM receivers equipped with an "SQ" decoder, resulting in the generation of outputs in the quadraphonic "SQ" listening system which reproduce the directional characteristic of the original sound sources. Thus, the system performs the function of a conventional multimicrophone and encoder system for "SQ" recording or broadcasting.

Abstract: Method and apparatus are described for translating or "encoding" the left and right signals from a stereophonic source such that when the signals are reproduced by a four-channel decoder the resulting sound field is highly simulative of that produced from a quadraphonically-encoded record.

Abstract: Apparatus for decoding four separate channels of information transmitted on two channels or transduced from a medium having only two separate tracks and presenting it on four loudspeakers to give the listener the illusion of sound coming from a corresponding number of separate sources. The realism is enhanced by a decoding matrix which accepts the two outputs from the medium, which may be a stereophonic disc record, separates them into four independent channels each respectively carrying predominantly the information contained in one of the four original recorded sound signals, and, utilizing a logic network which senses the signal amplitudes and phase positions, derives control signals for controlling the gains of amplifiers associated with the four loudspeakers. The logic control circuitry improves the realism of four independent channels by essentially eliminating undesired cross-talk which may accompany the signals produced by the decoding matrix.

Abstract: A pressure gradient directional microphone of the moving coil type in which the acousto-mechanical function of the transducer is achieved by a vibratile diaphragm the major area of which is of coneiform shape and the central portion of which is of dome shape and of significantly smaller area and provides a surround for attaching the coil. One side of the diaphragm is exposed to the sound field surrounding the microphone, and the other side is exposed to two cavities, one of relatively large volume behind that portion of the diaphragm which is of coneiform shape, and a second behind the dome portion which is sufficiently smaller that it is unnecessary to provide any phase-shift action for any sound pressure generated therein. The diaphragm is secured at its periphery to a support ring having a plurality of openings formed therein which serve as acoustic ducts from the ambient into the larger cavity.

Abstract: A compatible four channel sound system for use in conjunction with a recording system for recording four individual audio signals designated L.sub.f, L.sub.b, R.sub.b and R.sub.f on a recording medium having first and second primary information channels and first and second subsidiary information channels, the first and second primary information channels carrying information that is consistent and compatible with existing monophonic and stereophonic standards. In accordance with the preferred embodiment of the invention, means are provided for forming a first composite signal designated L.sub.T which contains, to the extent they are present, L.sub.f in a dominant proportion and L.sub.b and R.sub.b in sub-dominant proportions, L.sub.b and R.sub.b being phase shifted with respect to each other. Means are also provided for forming a second composite signal designated R.sub.T which contains, to the extent they are present, R.sub.f in a dominant proportion and L.sub.b and R.sub.b in sub-dominant proportions, L.

Abstract: A compatible four channel system for use in conjunction with a radio transmission system for transmitting four individual audio signals over a medium having primary and secondary information channels and first and second subsidiary information channels, the primary and secondary channels carrying information that is consistent and compatible with existing monophonic and stereophonic standards.