I stumbled onto this thread and wanted to add my 2c.
I'm a horn guy, for mid/hi at least. I recently tried the new-kid-on-the-block ring radiator compression drivers (Eminence) since I'd always wanted to try a ring since seeing photos of the 075 looong ago. I put them on small screw-on CD horns I was using already, replacing a good standard-design compression driver. The results were very good. I won't go back.
As mentioned earlier in the thread, though, they can be overbearing. I used a Nelson Pass 'trick' I already employed on my prior drivers in which it was suggested that a certain resistive load in series with the driver, when using an amp that behaves nominally like a voltage source, will simulate the behavior of a current source. I made no attempt to perfectly match anything; I simply used a noninductive 8 ohm power resistor. As with my prior drivers, the 'edge' was taken off. It's not the slight amplitude reduction nor is it anything I see on a scope (either from the amp or from a microphone), and I don't care whether the amp acts as a voltage source or a current source, but the effect is very pleasing, and the new tweeter sounds better than anything I've used prior. It runs from 2400hz on. The crossover is active digital, a 90db/oct FIR filter, just to fill in the details.
