I have built 8 of his Tuba 30 slims. They are the 24" wide version. They have JBL 2206 12" inside of them. Powered by a QSC 3402. Depending on configuration of the system we use, that gives us anywhere from 700 w/ch to about 1100 w/ch, running in stereo. The reason for 8, is 2 per system, with our small packages, or 4 per system with our larger sound systems. He recommends that you group them together, but we tend to break the laws of physics with the way we set things up.
They are very efficient, and original ran them with lower wattage, but found that the JBL's really liked the power, and so transitioned to the larger 3402. They have amazing, clean bass. Especially at low dinner music volumes. You can hear every tone of a bass guitar at the other end of the room during dinner. Simply amazing.
When you turn them up, they are clean, very clean. Low bass, but NOT the distorted bass that most DJs are used to from front loaded 15" or 18". This is clean, tight low end... not a "one note" wonder sound like a B-52 or CV, or such. The overall system is smooth, very smooth.
The key is that you can build one of his designs at a cost that will perform equivalently to a $2000 or $3000 sub, without the cost. He recommends Eminence drivers, but driver specs are good with JBL and maybe one other line. You can also modify the designs to make them easier to transport, lift, roll, pack, fit through a door, etc... sort of customized to your needs.
I'd say your wood working skills need to be above average, and that you need to READ the plans multiple times before you begin cutting and building. If you have ANY air leaks, the design will NOT perform, and you will NEVER be able to get back into the cabinet to fix the leak (due to the design). You can't just put any driver in them... they need to have strong motor capability of the driver with a high Xmax, if they don't you'll blow the drivers apart quickly due to the pressure generated in the cabinet. You need to do your homework. Depending on the cabinet you choose, the horn wave length could go from 5 feet to 7 feet in length... something you will NEVER find in another cabinet commercially produced.
Some coat them with Duratex, we chose to cover them with carpet for better durability and less slippage when packing things on top of them in transit. Baltic birch would be too heavy a build. He recommends 1/2" all the way around, inside and outside for most of the designs. We chose 3/4" ply for the outer shell, but did the inner horn shells with 1/2". The total weight, with the driver and hardware shown in the pics below was 85 lbs per sub. Specs for the wood need to be greater than 5 ply (???) I believe, it is 5 or 7 ply. We used maple wood internally (1/2" at 9 ply) and 12 ply 3/4" for outside.
I've attached a pic or two below of our finished product.
