3 three channel system, anyone?

Stanwal...If you use a simple Y interconnect you have shorted the Left and Right together. ALL channels will be Left plus Right... in other words Mono. To mix Left and Right so as to get a center signal without screwing up the Left and Right you must use a resistor network.

In my opinion the simplest and best way to drive three front speakers is to use a stereo power amp with the signal of one channel inverted. Bridge the amp with your center channel, and reverse the speaker wires on the channel that you inverted. Your amp will see a low impedance load, but I never had a problem even with 4 ohm speakers.

Another way is to connect the three speakers in a Y configuration. This will not lead to a low impedance load,

Magfan...What you did was basically the "Dynaco" setup, also attributed to Hafler. The Dynaco setup also included a Y-connected center front, which increased the load impedance of the front speakers so as to compensate for the series-connected rears that were bridged across the amp. Dynaco also suggested a "blend" resistor at line level to restore Left/Right separation which is reduced by the Y connection, but I always prefered the sound without the resistor.

With certain recordings the results were superb.

Magfan...There were two basic approaches to early multichannel...matrixing with many variations but most notably SQ, and the discrete system you mention. Information for the rear channels was carried by FM modulation of a carrier between 20 and 40 KC. Because it was FM there was no requirement for low distortion in the 20 - 40 KHz range, so long as the carrier frequency could be tracked. The need for response to 40KHz spured great improvements in phono cartridges which benefit us today although the multichannel scheme was a bust.