@clio09, interesting that both Roger and Bruce Thigpen ended up going with an 8" woofer in a small sealed enclosure to mate with their respective planars, Roger’s ESL’s, Bruce’s magnetic-planars. I deeply regret having been unable to hear Roger’s ESL driven by his direct-drive OTL amp. Now THAT’S the way to make a loudspeaker!
Danny Richie uses a pair of OB/Dipole subs up front (each sub having a pair of 12" woofers), and a pair of 12" sealed subs in the rear, with the rears in polarity opposite that of the fronts.