The 8 inch Tang Bands are in their own separate T shaped OB which just rest atop the H Frames. They are driven by a Miniwatt SET of 2.5 watts, while each 15 inch Eminence Alphas H frame is powered by a Dayton APA-150 amp with built in crossover. A crossover setting of 80 db sounds about right. The signal from an Integra player is feed to the amps via an Aric preamp.
In building the H frames and the Tang Band baffles I used a Kreg Pocket Hole Jig to make very strong right angle joints. It's by far the easiest and most fool proof way of joining two pieces of plywood together. If you've never seen a Kreg Jig in action they are several demos on Youtube. Best $90 I've ever spent.
I used inexpensive 3/4 plywood which can be had for $26 at Home Depot for a 4X8 sheet. It doesn't stain so well hence the painted surface and black molding trim.
I've had the Tang Bands in those folding wing OB's as shown in the background ( first pic ) but as you might expect they were bass shy. The H frames OTOH give great realistic bass and sound nothing like a plodding sub.
The H frames are quite versatile and I use them to add musical bass not only to the TB's but to a pair of Mk3 Frugal Horns as well as some small Tekton full range speakers.
Open Baffle speakers are often criticized for lack of a low end but the H frames offer an outstanding solution.