In reply to:
...the above statement is not correct...by definition, the optimal positions for surround speakers when listening to high res 5.1 music tracks are slightly behind (30 degrees) the listening position, at ear level...
It's actually not that clear cut. THX head Tom Holiman says about 90 degrees is best for side imaging. You could argue that's for movies, but the issue is best side imaging, which you want for music.
http://www.smr-home-theatre.org/surround2002/technology/page_00a.shtml
Composer and audio researcher Wendy Carlos calls putting surrounds at 135 degrees "the worst possible surround setup", and says roughly 90-110 degrees is much better. Other researchers including Lexicon's former head designer corroborate this.
http://www.wendycarlos.com/surround/surround.html#digress1
I've tried both ways, and especially for music I agree with the above researchers -- about 90 degrees works best for me.
If anybody wants to put the surrounds behind them for music, feel free to do so. However I strongly suggest you do some listening tests before drilling holes and pulling speaker wire.
