I was looking around for speaker plans, and I stumbled on this listing:

http://zmatek.jinak.cz/diy/

Then I clicked on a few links, and I found http://zmatek.jinak.cz/diy/elektro_archiv/900l.jpg and I thought it looked familiar.

Is that one of the imperial designs?

Stv

I think it's an Imperial variant.
I've lost the DIY site link, but I've seen a very similar box, scaled up to use a 24" or 30" driver. He was using a full 4' x 8' sheet of plywood for the sides and several hundred pounds of sand in the voids.
I turned green.

Thats the one I was thinking of.

the smaller compression chamber reflects a smaller driver and differant horn.
My guess ( guess) is it is tuned higher.
I have seen that one before but never looked at it that close before. I prefer Steves right off and simplier too.

selmerdave wrote on 11/26/05 at 04:27:38:

I know this is a two-year-old thread, but I'm hoping someone will explain the difference between the 1952 version in those bulletins, and the 1954 version!  I own two of the March 1952 version cabinets, and am very curious what was done in later Jensen designs.

Thanks, Dan!  I would love to compare the same driver in different cabs... but am very happy with the Tannoy Monitor Gold 15s in mine.

It would have been a lot less confusing if they had used distinguishing names consistently.  "Imperial" is not in the 1952 brochure.  That 50"h corner version is clearly labeled an Imperial, but if they are counting the legs in the height, the cabinet is more like 44" in height...

If someone has a link to a ~ 60 x 36 x 24 rectangular BLH cabinet that differs from the 1952 drawing, I'd sure like to see it.

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 ...