The most exotic tweeters might not produce the results one is after. Some of the simplest tweeters seem to do a great job.
I was on that metal driver kick for a while. But then, it was appearent that the implementation of the MIDRANGE with said tweeter is just as crucial as a tweeter itself.
IMO, the Wilson products utilize the Focal tweeter better than JMlabs do because the Wilson midrange is better. At least it sounds faster/more detailed/better integrated to me anyway...
The Vandersteens use scan speak, and Vifa aluminum in thier glorius model 5. IIRC VonSweikert did/does also. Not an expensive tweeter, but a killer implementation.
Sonus Faber does dynaudio and silk tweeters well.
The ATC's I bought seem to use a simple [looks like a modded vifa] 1" soft dome tweet. They make their own mid range. They blend togeather so well, the mids are free of colour, transparent, and very detailed with extended treble...and no metallic edge.
The ATC intruiged me, because like other well-done designs, they produce outstanding results without resorting to $695 or $2500 tweeters.
Recently though, HIFI News proclaimed the JM labs micro utopia BE [Beryllium tweet] possibly the best compact two way ever.
Bold claim, I will believe it when I hear it. Because the Be series seems to use the same mid as the Utopia did before. I am skeptical that a tweeter alone would place it on equal footing to the Wilson watt.