Unusual Old School Way of Wiring Speakers

I'm not having any luck finding anything about it, but I thought I read about connecting a rear speaker to one of the outputs (i.e. lefts or rights) from the main speakers with the result being a bit of a phantom channel the added some depth.  Does this sound familiar?

Is this what you’re looking for?

That’s the old DynaQuad hookup devised by Dynaco to be used for a rear pair of speakers to add ambience. Dynaco sold an adapter box for this purpose. I recommend searching online (eBay, etc) and buying the DynaQuad box to experiment with.

What the Dynaquad box does is create a left minus right signal (the opposite of a left plus right mono one, as used for the center speaker in 3-channel stereo---somewhat popular in the 1950’s, and of course in home theater for the dialog channel). That signal is then sent to a separate amplifier powering a pair of rear loudspeakers.

The box includes a volume pot on it’s faceplate, necessary to allow balancing the rear loudspeakers with the front pair. The box receives it’s signal from the power amp---a high-level source, of course. In the 1980’s Acoustic Research introduced a box which produced the same left minus right signal, but did so at line level, taking it’s signal from the pre-amp. It was intended to be a cheap way to create a home theater-type surround sound effect, but can also be used to create "spaciousness" from 2-channel sources. That box (sorry, I don’t recall it’s name/model number) and the Dynaquad box can be found for not much dough.

That pair of rear channel speakers (it has to be a pair) reproduces and reveals any out-of-phase information/sound sometimes found in stereo recordings, a random phenomenon. Out-of-phase information is not-uncommon in recordings made in large venues: concert halls, cathedrals, etc. It is less common in close-mic’d studio recordings. A cheap, fun way to create an "immersive" sound field!

Whew!!! I'm glad I'm not going crazy and making stuff up in my head...about this anyway. Thanks everyone, this is the info I was looking for... Just for the fun of it, I'm going to play with this in my office system.