Kenwood QUADRIX
KA-8044
KN-7044
KM-8022
(1971)

Early Kenwwod QUAD components - the first ? Buttons, buttons, buttons at any rate, and more buttons, controls and displays.
So the KA-8044 is a Surround Sonic Quadrix Amplifier (not to be confused with integrated amplifier - the latter being of the same family tree but way older, just next to the beginning of the second ice age) and the KN-7044 is a Surround Sonic Quadrixer - sic transit nec mergitur.

Both of these pre-Star Wars launch pads could be fed with Discrete 4-channel, Encoded 4-channel or Synthesized 4-channel. Both could dub 4-channel to "encoded 2-channel", too. Both could add Hall reverb to the rear channels, complete with level, mix and balance controls. If early ref' and Q controls were the next decade, at this level of complexity, specs are already a mere triviality.

But think of the engineer who spent weeks making the ultimate mix, only to hear it "improved" by tech-trek audio fans spreading that magnificent in-phase mono voice take all over their untrained bedrooms ! And only to benefit from the resulting aural fireworks completely isolated between their four Quadrix loudspeakers ! Quite surprisingly, Quadrix could lead back to... mono.