One thing with that SB Acoustics ring radiator is that maybe it does have a remarkable Fs of 680Hz and is capable of going quite low, but it sounds ten times better as a supertweeter, with lower frequencies kept firmly out of it. Upper harmonics are exquisite with not a trace of hardness or fizz if it is used that way. Just because the thing can go low, does not mean that you should make it so.
If in the context of an omni speaker, this excellent ring radiator is used in conjunction with a swivelling cone, that takes lower treble and upper mids in its stride, the resulting tweeter array sings in the highs, offering beautiful string tone, fab cymbals, detailed tinkly bits, and excellent upper registers of female voices, and won't descend into nasality or sqwawk. The efficiency of the tweeter array is also enough to blend in seamlessly with a high sensitivity up firing bass/mid driver, running wide open.
What I'm talking about here is peculiar to omnis and semi omnis and has absolutely no application for front firing speakers, which if made up of high sensitivity bass/mid drivers, to go with low powered single ended valve amps, would just drown out the treble units; compression drivers, horns or high efficiency ribbons are required for those.
Most DIY audiophiles have no interest whatever in omnis or semis, never will, and who can blame them. The things are an absolute bastard to design and voice up. Only a few crazed eejits would be daft enough to take on the design of one. But once you crack it....
Anyway I think I've said all I want to say about this rather controversial way of reproducing recorded music in the home, it's become a tedious hobby horse that has been done to death, so I'll spare you lot any more of my blithering about it.
Good luck with the baffle reboot Ed.
Sgt. Baker started talkin’ with a Bullhorn in his hand.