GB1367191A - Multisound reproducing apparatus - Google Patents

Abstract

1367191 Stereophonic systems SONY CORP 13 April 1972 [13 April 1971] 17139/72 Heading H4R Stereophonic reproducing system feeds conventional L and R channel signals through phase-shifting circuits 61, 62 to be reproduced by respective speakers 1, 2, mounted left and right front of a listening area, while deriving a filtered signal La, Ra, from each channel and combining it with a phase shifted signal Rf, Lf from the other channel to feed further speakers 3, 4, mounted left and right rear of the listening area. The filters 83, 84, preferably are low-pass filters and the phase relation of the combined signals fed to the rear speakers is such that similar signals in the two channels cancel at about 700 Hz. In a preferred arrangement, Figs. 6 and 7 (not shown), the circuit includes switching and additional phase shift circuits to allow selectively dematrixing of matrixed quadraphonic signals or reproduction of conventional stereophonic signals on four loud-speakers according to the invention. As described with respect to Fig. 1, the L and R stereophonic signals from amplifiers 51 and 52 are fed to phase-shift circuits 61 and 62 which produces a phase shift varying from 0 to 360 degrees over the audio band the resulting signals Lf and Rf are fed via power amplifiers 71 and 72 to be reproduced on front loudspeakers 1 and 2. In addition the L and R signals are fed through low-pass filters 83 and 84 having a phase shift which varies from 0 to 90 degrees over the audio band such that the signals applied to each of the adding networks 93, 94, have been relatively phase shifted by 180 degrees at about 700 Hz. The outputs of the adding networks are fed to loud-speakers 3 and 4, mounted at the rear of a listening area, via power amplifiers 73 and 74. A circuit for the phase-shifters, adding networks, and filters is described with respect to Fig. 7 (not shown) which includes further phase-shift networks for decoding CBS (Registered Trade Mark) matrixed quadrophonic signals.