I've seen both dipole and direct radiating suggested for surround back, but never heard an argument that made one clearly better than the other. In my case, the single dipole surround back has worked out very well -- it's a good match to my (identical) surrounds, and it blends in well (diffuse enough to not stand out as "I'm a single speaker back here on the wall, which I think is partly due to it being a dipole). In fact, in my current space, there isn't room for 7.1 (the surrounds and surround backs would start getting absurdly crammed together). If I were doing two surround back channels, I would look into the possibility of using direct radiating, but I wouldn't dismiss dipole even then. For now though, I'm very content to have my solo dipole back there and don't plan to change any time soon.

One thought that occurs to me for a 7.1 speaker arrangement is this: dipole surrounds and direct radiating surround backs, with a switch set up to allow the surround signal to go to the direct radiating instead of the dipoles for 5.1 music (DVD-Audio, SACD). I don't know how much benefit it would offer (could potentially end up with the direct radiating speakers in a bad location for one of the two applications), but I have a lot of interest in direct radiating for multi-channel music surrounds. Call that Friday's random idea of the day...

------------------
gonk -- Saloon Links | Pre/Pro Comparison Chart | 950 Review