2 Pre-Outs?

The difference in phase is what we are talking about, just like you said in both of your posts. Also, the difference isn't large at all - it all comes down to playing with just a few milliseconds.

Using the B-speaker outputs works very well for surrounding yourself with sound. I don't know if you have actually tried it but I have and it sounds rather realistic if you get the positioning right.

Of course, I am only talking about music, like Drmoles is, so you can't expect there to be any sort of "decoding" needed - just a few milliseconds delay to create a feeling of ambient space and that is pretty easy to do.

I'm a bit confused. Are you passively bi-amping one pair of speakers, or, are you simutaneously running two pairs of speakers?

I agree that cancellation and phase variations are at work. 2 outputs are generally used when bi-amping or running 2 rooms... I have stacked 2 pairs (years ago) and achieved ok results but ultimately what you are trying is an '80's idea. Using a 2nd pair of back speakers (with much reduced volume) to produce 'ambience' and 'space'. Running both pairs at matching volume is very hard to pull off.

Well guys! Call me crazy if you want, but at the present I am running 3 systems at once; yes, 3.
3 Preamplifiers, 3 amplifiers & 3 pairs of loudspeakers.
All the loudspeakers have a different positive as well as a negative sound quality to it.
One system consists of a Jeff Rowland Concerto Preamplifier, A Jeff Rowland 112 Amp hooked to JM Labs 937 BE Anniversary Edition.
The second system is a Jeff Rowland Consummate Preamplifier, a Jeff Rowland 112 amplifier hooked two a pair of Aestheth VI Elite Loudspeakers.
The Third system consists of a Antique Sound Labs Otl 32 preamp (also can double as headphone preamp), a Cary V12i Amplifier (running in triode mode) hooked to a pair of System Audio 1532 Loudspeakers.
All sources are daisy chained thru the systems with Crystal Cable, Loudspeakers use Soundstring Cables.
I am using the 2 outputs of a Cayin SACD player.
I can play each sytem separately or all played at once at different gain levels.
I have failed to notice any Phase problems.
So, call me crazy since it sound like a derranged idea. But I call it Synergistic sound arrangement like in a good and well tempered choir.
By the way, I did not have to spend the money on a pair of Wilson Alexandrias or Grand Slamms and other exotic sound gear.

This sounds like a Rube Goldberg project. :)

Seriously, along with the issues previously mentioned I'm wondering if there is something going on with the sensitivity between pre and amps when you try to run everything together. Don't know where you're trying to get to, but have fun.