So, I got my '4-channel' stereo running. It's pretty good, and POWERFUL! But, with the lack of a discrete 4 channel source, it's little better than Stereo, unless you use one of the 'tricks' built into the amp. It has Matrix SQ and Quatravox. Matrix SQ was a industry standard to take a 2 or
4 channel source and 'synthesize' 4 channel. It works OK. Quatravox was, IIRC, developed by Radio Shack and is like "Stereo Wide", it takes a 2 or 4 channel signal and plays with phase relationships to synthesize and expand a 4 channel 'image'. It works OK but you can hear the phase shifting.The real question is this: I used to take a stereo for my car and install new speakers, esp. decent speakers for the rear deck. In the '80s Matt Polk came out with his 'imaging' speakers, and they were GREAT. But, you had to sit in an exact location to get the effect. If anyone remembers these, they made the band appear to be positioned around the room. It was
100 times better than headphones.He did this by feeding a 'component' from the opposite channel to the other channel, at a lower volume. This cancelled out crosstalk and made pure left and pure right from each speaker.
So, I would add a pair of 6x9 speakers to the rear deck of the car. Since I almost always had hatchbacks, this would leave the original speakers in their original locations. So, here's what I would do:
I would add an amp, sometimes two, one for the front and one for the rear. By tapping the RCA outs from the preamp, this left the 4 original powered outputs from the stereo intact. So, I would take the stronger channel, usually the rear, and cross the speakers left as right and right as left. Since I had 65-75 watt amps, and the outputs were typically 12-20 watts, there was a 'deficiency' from the head unit's amp. Now for the trick: I would put the car's original speakers out of phase. Then by playing with levels and balancing, I would 'even' the system out. I never really acheived the effect of the Polk speakers (I was trying to emulate $1400 speakers with $100 worth of components...) BUT, what it did do was to make it appear as if the speakers were about 4 feet 'outside' the car. This effect worked fairly well.
So, my question is, although I never appeared to do any damage to anything (I ran this setup in my 'Hachiroku' for four years until the system (and, indeed the whole car!) got ripped on Good Friday night. I got the car back but never really built the stereo back up.) Since the RCA outs are picked up at the preamp, and are a voltage with no 'load' associated, this left the output stage virutally untouched.
Since the speakers were balanced amp-to-amp (ie, 4 ohms wired to the head unit amp, and 4 or 8 ohms to the external amps), are there any ill efects to putting speakers out of phase. In case you don't know what this does, let's take the woofer: when the 'in-phase' side is pushing out, the 'out of phase' side is pulling in. Since the load is balanced reactance-wise, there SHOULD be no ill effect on the amp.
Right?