Tried 2 pairs of speakers for 2 channel?

www.space-tech-lab.com/IMPROVETIP.HTML
You might want to read the number 7 tip from the above site. It touches on placement of two pairs of speakers, placement and wiring. Sounds interesting, although I personally have not tried it.

I have built several experimental bipole systems.

One disadvantage of a bipole setup is that you will probably get a severe dip in the on-axis frequency response at the frequency where the path length difference from the woofers to your ears is equal to 1/2 wavelength. The dip would probably be in the lower midrange or upper midbass region.

It is possible to design a system that minimizes this path length difference dip (and indeed Definitive Technology holds a patent on one such technique), but you have to design the system specifically to address that issue. It is very unlikely that placing two identical speakers back-to-back would work.

You may still like them in bipole configuration, as dips are less audible than peaks.

Duke

i owned 2 pair of quad esl 57 speakers, which were stacked in a mark levenson stand.

as an experiment i tried running 2 pairs of different speakers, one behind the other. yes, i am aware of the problems. it was just an experiment--an interesting one at that.