Hey John - I'm glad to hear about your experimentation. I wasn't trying to replace or bad mouth the CPS approach when I started that thread. My main intent was to show several easy ways to obtain the L+R, L-R signals with components most people have at hand. My approach did not include the R-L signal, although that is also easily achieved. It does however provide a nice alternative for adding some stereo effect.
The easiest way to sum up (no pun intended) my method is to run L&R into a stereo mixer that has a headphone (or equivalent) output. I then took the Separate L & R outputs from the mixer into Inputs 1&2 of my ELX112P. I set the input levels equal and this provides the mono (L+R) signal.
Then I used a TRS cable to connect the headphone out from the mixer to a separate powered speaker. The TRS cable carries the L channel on the tip and the R channel on the ring of the cable (or vice versa). Any powered speaker will work as long as it has a differential (balanced) input. The subtraction process of the differential input results in the second speaker amplifying the L-R signal.
I used a small Behringer 150w monitor because that's what I had. This is NOT identical to true MS matrixing but definitely adds a nice stereo component to the EV. It is also easy to adjust the level & EQ of the L-R signal. It is also REALLY cool because I could turn down the EV (mono signal) & just listen to the L-R channel. This actually provided some insight when programming sounds as I could hear the isolated signal when applying stereo effects. Of course the output of the second speaker is quiet with a mono signal.
Of course you could then take the linked output from the Behringer, invert the signal and feed another powered speaker if you like. This would result in the R-L signal. Now you're up to 3 speakers but the fun is just beginning.
Anyway I hope this possibly inspires somebody to do some further experimentation.
Larry