GB894601A - Improvements in stereophonic recording and reproduction - Google Patents

Abstract

894,601. Stereophonic systems. WEIZMANN INSTITUTE OF SCIENCE. April 1, 1959 [April 1, 1958], No. 11082/59. Class 40 (4). In a stereophonic sound transmission system separate microphones are provided for different frequency bands and are spaced from one another, their outputs being fed to similarly spaced loud-speakers each responsive to a different frequency range. In a first embodiment six microphones 1 to 6 are spaced as shown in Fig. I, microphones 1 and 6 being connected to lowpass filters 7, 12 having a pass band of 30 to 350 c/s., microphones 2 and 5 to high-pass filters 8, 11 (above 1500 c/s.), and microphones 3 and 4 to medium-band filters 9, 10 (350 to 1500 c/s.). The outputs of filters 7, 9, 11 and of filters 8, 10, 12 are fed by way of mixers 13 and 14 to the amplifiers 15 and 16, respectively, of two channels 17 and 18 and thence to receiving amplifiers 19 and 20, respectively. The outputs of these two amplifiers are fed via filters 21 to 26 to six loud-speakers 27 to 32 each loud-speaker reproducing the same frequency band as does the correspondingly situated microphone. In a modification (Fig. II-not shown) the microphones 1 and 5 are retained together with microphones 3 and 4, but microphone 3 is associated with a low medium band filter (200 to 700 c/s.), microphone 4 with a high medium band filter (700 to 2000 c/s.), microphone 1 with a low-pass filter (30 to 300 c/s.), and microphone 5 with a high-pass filter (above 2000 c/s.). The outputs of the four filters are passed via a mixer to a single channel having transmit and receive amplifiers and the output of the latter is fed via low, medium and high-pass filters to three loud-speakers corresponding to 27, 29 and 31.