GB1385651A - Matrices and decoders for quadruphonic sound systems - Google Patents

Abstract

1385651 Four loud-speaker stereo systems CBS Inc 2 Feb 1972 [3 Feb 1971] 4974/72 Heading H4R In a matrixing system for combining four signals, designated Lf, Lb, Rf and Rb on two transmission channels the signals are combined and subjected to differential phase shift in such a way that on one channel is transmitted major portions of Lf and Lb signals with minor proportions of Rf and Rb signals and with the phases such that Rf and Rb are in phase opposition with each other, and in quadrature with the Lf and Lb signals, while on the second channel is transmitted major portions of Rf and Rb with minor portions of Lf and Lb, the two latter in phase opposition with each other and in quadrature with the Rf and Rb signals. Fig. 4 shows a block diagram of the coding matrix and Fig. 6 a suitable decoding matrix which combines the signals so that each output contains a major component, e.g. Lf, with smaller amounts of adjacent signals, e.g. Rf and Lb, but with cancellation of the diagonally opposite signal, e.g. Rb. In the coder of Fig. 4, the main components in each channel suffer no relative phase displacement but in an alternative arrangement, Fig. 7 (not shown), the signals are phase shifted so that the main components in one of the two channels are displaced in phase by 45 degrees relative the main components in the other channel, the relation between the components in each channel being maintained as in the embodiment of Fig. 4. A suitable decoder is described with reference to Fig. 9 (not shown). The decoder may be provided with gain control logic of the type described in Specification 1,347,994, and suppleinentary phase shifting circuits to adjust the relative phases of the individual output signals.