I have a 7.1 speaker setup. The side surrounds are dipole-bipole switchable as well as the surround backs (Polk Audio FXi5). The side surrounds are positioned slightly behind my listening position and the rears are on back wall approx 8 feet apart. My room is 20x12. My questions is should I select the dipole or bipole setting on the speakers. I have tried both and cannot tell a huge difference between the two. Any help would be greatly appreciated