The Beyma AMT units are utterly gorgeous-sounding drivers - I cannot recommend them highly enough. Just two reservations, namely their cost, and a relatively low output compared with conventional HF options.
I found that, rather counter-intuitively, the system sounded better with a higher crossover frequency than Beyma specs. would suggest...
I believe Adam Audio use an ATM ( air motion transformer ) which is the same principle as the Beyma
Here is another manufacturer of ATMs - used by EM Acoustics in the Halo C http://www.mundorf.com/PDF/MUNDORF_proAMT_Catalog.pdf
It was a very simple rectangular ported box rolling off at 80Hz using a Beyma 10LW30N (also a very good driver) with the TPL150H on a bracket in free space on the top (used with sealed 18" subs from 80Hz down). Very much a 'quick prototype' build that got used for far longer than it should have been... Played mainly in pub gigs with a few low-level outdoor outings, where many commented it was the cleanest little mid/top they had heard! If you can afford to use Beyma AMTs I guarantee you will be converted.Got any designs you can share?