Originally Posted by Des Flurane
How about for a 6.1 setup?
I would avoid a single rear speaker if at all possible, because of a psychoacoustic phenomenon called back-to-front reversals. Sounds along the listener's centre line can sometimes be perceived as coming momentarily from in front (which is where our brain expects it to be), even if the actual speaker is directly behind or above. This doesn't happen with a single centre speaker up front because that's where our hearing is most acute.
The solution is as simple as it gets: just use two speakers behind you, spread well away from the centre line. This is the main reason why Dolby and DTS and THX all
recommend using two rear speakers, even for the mono surround-back channel of their EX/ES formats. Note that this is the only
channel for which two speakers are recommended for playback. And since you have a 7.1-channel receiver anyway...