I would absolutely agree that the TAD beryllium drivers are demanding and tough to match well with amplification, but I have found that to be a revelation of the amplification. My CR-1's really sang well with the D'Agostino Momentum S250 + HD preamp. No fatigue, listening sessions that went on all day just absorbed in the music. I think the slightly "warm" sonic palette of the D'Ag gear suits TAD well, and the amp has plenty of drive to keep the woofer up to speed with the mid/tweet.I owned the R1. Tried a heap of amplifiers but the end of the day the loudspeaker was not enjoyable for long listening sessions in my experience. The mids/highs too coarse. Music selection shrank due to some recordings being unlistenable.
I have had a negative opinion of beryllium since and only this year I heard the Beryllium tweeter from Von Schweikert and it changed my opinion again.
they have damped the beryllium (with ceramic I think) and the results are stunning. Have a listen to this tweeter to hear how beryllium can sound realistic whilst presenting a non fatiguing long term listening experience.
When I have the R1 I went away for a weekend, I spent a few days with another speaker which cost $27k. Far less than the R1 and I got much more from it. I promptly sold the R1 and never looked back.
No need to mention the name of the other speaker but to say R1 are competitive up to 400k is a bit of a stretch.
I have since moved to CH Precision 10 series amplification, and I have to say that these were not immediately natural partners with the TAD. I have since upgraded my system cabling to Elrod Master Diamond throughout and the TAD's are singing like I have never heard from any other stereo that I have experienced. Simply the purest, most natural sounding presentation, very informative, but always pulling me in to every piece, even on crappy recordings. They're incredibly truthful, and that might not be great for some upstream equipment. I think the TAD's won't please those that want a bit of euphony to enrich everything that comes through the system, and I get that. I used to be in that camp for 30+ years. But, IME, sort out the upstream stuff, and the TAD's simply reveal the beauty. In the past year I have started to enjoy fairly unlimited funds to apply to my audio hobby, and I plan to do so. I've been prepared to change speakers, if need be, as I elevate my system. I'm not sure I will be doing that, because the TAD's are holding their own. (OK, with CR-1's I plan to add well-sorted subwoofing, at the very least!)