I can't help notice a correlation between ultimate tweeter transparency and having to put up with harshness at loud volume levels. It can be very transparent and smooth to an appreciable volume, bit exceed that and it will go harsh if you apply the materials necessary for max transparency in those drivers.
I owned titanium dome tweeters in Avalon Eclipse speakers that ultimately caused me a case of a decade-long bout with tinnitus from the titanium dome tweeters, even when using a smooth Music Reference RM-9 tube amp.
I then owned a pair of horns with lightweight metal compression driver diaphragms. Again, unbearable harshness at loud levels where the metal "breaks up".
I now own a pair of beryllium dome tweeeters in speakers that again are volume limited before that metallic glare and harshness comes in. When I had silk domes none of that happened to me, but the details and transparency are markedly down for those drivers at all volumes.
The most transparent drivers I heard were the best tweeter horns but at the cost of harshness. They exceeded electrostatics for dynamics and transparency and detail, but at that cost. Electrostatics seem to me to be the best compromise in midrange on up detail and smoothness but with a real decline in dynamics.
Maybe diamond is the answer with its extreme rigidity and hardness. But I'm not rich enough for that yet, and probably never will be.
What's the scoop on the best tweeters out there for all of what I'm asking for here, but at a reasonable price? One possibility that intrigues me is the ceramic tweeter, but again, I don't know and those are not cheap either.
I want to play horns and cymbals loud and clear, without that bite in my ear. Soft domes aren't enough for me, at least not the ones I've heard after hearing horns and beryllium.