My wife wanted something not too obtrusive so these cabinets are only 32" tall. I cut all the cabinet parts myself from one 4'x8' sheet of 3/4" oak veneer plywood. Many internal parts too, that form the folded horn (Fostex has plans you can download). The corners are 3/4" square walnut strips, so no plywood laminations are showing. The drivers are Fostex FE126En. The drivers are 8 ohm, direct wired, with no compensation network. There is enough bass for me, tight and accurate, but no subsonics. The midrange is very dynamic, and the sound stage is detailed if you sit six or so feet back, and in front of the drivers. (Deffinately different from my Ohm Model F speakers, which disperse direct and reflected music in all 360 degrees). The highs do not quite have the champagne glass sparkle that a super tweeter would give them, but my old ears have lost some of that sparkle too. Never-the-less, a picolo still sounds like a picolo should. Everything is a trade-off, and what full range drivers do right, they do very, very, well. Dead on coherence, precise sound stage positioning that does not wander about (assuming the source recording was done well). They often have a few frequency "bumps" but so do "perfect speakers" when you take them out of the anachoic chamber and put them in your listening room. Tubes should not sound better than a well made solid state amplifier, but I think they do. A full range driver should not sound as good as a 36 driver transmission line speaker, but still some people like them.
I think the BK-20 (pre-cut) is Baltic Birch, which is good stuff. You can get birch veneer tape online to finish your plywood edges if you want to. The veneer tape comes in three forms, sticky adhesive backed, heat activated adhesive (iron on), or bare (glue on with wood glue). I think glue on is the only way to go, tedious to clamp, but does not come loose six months later.
If it is not making X-rays, your B+ is too low.