Wayne Parham Messages: 18789 Registered: January 2001
Illuminati (33rd Degree)
What you want for flanking subs are sound sources that are smooth through 200Hz or so. Pretty much any direct radiating sub will do that just fine, regardless of size. Most subs will, to be honest. The only thing I'd stay away from are tapped horns, which have too much distortion and upper-band spikes to be used as flanking subs. But direct radiators rarely have trouble reaching 200Hz, even woofers with heavy and/or large cones.
As for the more distant subs, any thing with good extension will do there. They're low-passed pretty low, so most any sub that can hit the low notes can be used for a distant sub in a multisub configuration. The goal of a distant sub is to smooth the room modes below 60Hz or so, and they are rarely used at high volume. They're there just to fill in the holes from the lowest room mode or two. So they don't need to be SPL monsters, but they do need to hit the low notes.