Beryllium Tweeters

My Yamaha NS1000m use those tweeters. Howevwr the B&W Nautilus 803 sounds way better.

I think dome compound is just a piece of the puzzle. I’m currently listening to a tweeter that’s made of aluminum, lithium and magnesium and hand on heart, my last 4 speakers used BE tweeters and I don’t hear any dropoff in detail coarse’ I probably can’t hear above 12k anymore. When I first heard the 1028be it was like a magnifying glass for my ears, but nowadays I think the rest have caught up. 
  

Given it appears in various sources that Materion (the sole supplier) is going to be discontinuing the manufacture of beryllium foil that is used in tweeters, is there any insight as to what will be replacing that material? Carbon fiber? Silk? 

Apologies if this is too off point.

Hi, first post here.

We do offer the BlieSMa 25 mm and 34 mm beryllium tweeters on our Sun Audio Purified 4 modular loudspeakers. Air and sweetness are superb. However, if you are looking for extension/wide dispersion, the T25A has a horizontal directivity of 160° up to almost 15kHz, and only -2dB @20kHz and 60°. 

HiFiCompass has published a comprehensive review of the BlieSMa tweeters.