Thanks again, Dan! For the first time, I think I'm beginning to glimpse the many Imperial designs and how they got that way. While actual cabinets built on any of these designs are not commonly found, I'm beginning to think that particularly few of the 1952 design were actually built. You ask a good question, though: was the elimination of many chamber pieces in the 1952 design primarily for ease of construction by DIY guys, or were there good sonic reasons?
I once tried a 12" EV coax in my cabinets. Mounting was easy because the driver was already mounted to a large panel, so I just bolted it to my existing baffle board. BIG FLOP. Not much good was happening. Immediately after mounting one and trying it, my buddy and I rear-mounted one of his Tannoy 3808's on the existing baffleboard, and it was really REALLY good right off the bat. So we put in the other one, using the monitor crossovers, and were astounded at how good it was. But the point I want to make is that the 12" in a cabinet designed for a 15" was a total mismatch, with the chamber behind. I could have improved it greatly, I guess, by filling it to occupy some volume, but I thought -- why bother? just go with 15"s.
So ... I wonder about using a single 15" driver in the Decware Imperial designed for 2 15"s. Wouldn't the increased chamber volume make that sub-optimal? To put it another way, if I'm trying to make the most out of a single vintage dual concentric per side, isn't it possible that the 1952 design I've already got may work as well (with adequate bracing) as the Decware Imperial, and maybe even better? Not that the old design is better, in any absolute sense, just a better match for a single 15".
The 190 lb. Tannoy DMT 215 speaker (
http://www.primalgear.com/tannoymon007.html) uses a 15" woofer along with a 15" dual concentric (3833GG as in the DMT 15, I think), so there's a sort of design parallel with the mismatched 15"s people use in the Decware Imperial. But those particular drivers are kinda high on the Qts, and are probably better off in the box they come in. Still, I suppose one could build a sort of "vintage-style DMT 215" by using a Monitor Gold along with an appropriate woofer in a backloaded horn ...