This is a system to control distribution of signals to multi-channel loudspeakers placed, presumably, at multiple locations in a performing space. The lower component, marked "voltage source", offers 20 independent DC control voltages, organized into four banks of five speaker system signal sources (left-rear, right-rear, left-front, right-front, center "(if used)" ). This is a matrix which ultimately drives four (or five, if center channel is used) power amplifiers.
The mixers are 6-in/4-out, with only two of six channels of knobs drawn in for each mixer. The upper component (represented by two mixers and a "distributor") appears to take 12 inputs, presumably organized as 4 channels x 3 inputs/channel. I think the center-channel is derived through some sort of summing within the "distributor", and the mixer presents four channels of audio to the distributor. It busses the four mixer outputs across the distributor, making each buss available to all 4 (or 5) speakers (assuming all 20 of the DC control voltages are ON). At this point, each of the four (five with center channel) power amps could receive all four signals. However, it appears that the user, in real-time, manipulates the pots (on the "voltage source" panel), such that varying amounts of signal are sent to the speakers from each of the four busses.
The control panel has four groups of six pots for each of the distributor busses. Each group controls one of the four busses, and each of the group's five smaller pots admits a desired amount of signal, from that bus, via VCAs, into one of the five power amps. Each group has a master pot, which in effect gangs the control of the voltages from the five pots in the group. With this system, sound images from each of the signals could be made to move around the hall. There is a wealth of control over spatialization of sources here.
The box in the upper right is a little mysterious. It could be a power supply for the entire system, but it appears Mr. Tudor went to great lengths to represent a loudspeaker system (he's drawn what appear to be speaker drivers). DC voltage entering a speaker system implies an internal amplifier, or the presence of at least one dynamic driver (a speaker driver which uses a DC powered coil rather than a permanent magnet).
-Bob Falesch (R. Albert Falesch)
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