Originally Posted by Lastyear4gt
You'd aim them cross firing?
Yes. Speakers are typically loudest on-axis (pointing directly at you), and start getting quieter as you rotate them off-axis (away from you). Likewise, speakers sound louder when they are closer to you, and start getting quieter as you move them farther away.
If both your rear speakers were pointed directly forward, then the listener on the left side of the couch will be dominated by the sound of left rear speaker, for two reasons: it will be on-axis (pointed directly at his head) AND closer to him than the other rear speaker. Double whammy.
However, if you point that left rear speaker at the listener on the right side of the couch, then you trade off some of the energy of the closer speaker by hearing it attenuated off-axis. Even better, the rear speaker that is farther away is pointing directly at you, compensating for the distance by hearing it louder on-axis.
For the listener seated in the middle of the couch, both rear speakers will be equidistant and sound balanced. It is the listeners on either side that will thank you, for having a more balanced rear soundstage (by keeping the nearby speaker from dominating). You might want to consider this for your side speakers as well, if they are mounted above ear height.