Plato and Sean pretty much said it all, I would only add that the sub should not fire at the front speakers, face it to fire across the room. The sub should not really be placed in the rear of the room for music at all but could work out well for movies if you run your front speakers full range.
Can my subwoofer sit right next to me?
I have a RBH 1010SE subwoofer with 12dB crossover set at 80Htz. Would I be able to place the sub in the rear corner (facing towards main speakers) right next to a recliner chair and not be overwhelmed by its output assuming the level is set properly. The main speakers are rated at a low frequency of 27Htz. + or - 3dB. The subwoofer has 2 10" drivers and has a port facing in the same direction as the drivers