A few people have asked me about this, so here's some info on it. As usual, the design was done with the woofer and SEOS12 mounted on the same plane (inset equally). The result ended up being smoothest slightly above center of the waveguide (lobe going a little upward), so you might want it to be positioned a foot or so below ear level. Or you could alternately inset the Celestion 15" a little more (or back mount it, if the baffle's not too thick). The box we used was 2cuft sealed, which checked in around 75Hz f3. If you really want it to go deep, make a 13cuft box and port it! Divorce may be required, though. That woofer turned out to be quite sweet. Very nice smooth midrange, well behaved before it rolls off naturally around 2kHz (actually easier to design with than the TD15M, which has a lot of junk to get rid of above crossover). I may like it better than the TD15, actually, but remember I'm not a high-volume freak-- TD15 may do better if you're wanting your neighbors down the street to hear it clearly. That's a pretty nice result for inexpensive drivers. Check out the smooth phase response! Erich has the one that was built, haven't heard this in stereo but there's no reason to think it wouldn't be pretty fine. Maybe if Erich can tear himself away from outside work, he'll get around to making up a second one.