Beryllium Tweeters


I've only heard Paradigms Beryllium Tweeters but I absolutely loved them! What other "affordable" (>$2k new or used) speakers use them and what are your experiences with Beryllium tweeters? What other Tweeters rival the extension, air and sweetness that I was hearing with my Paradigm Sig 2's? DeCappo? Usher? ...?
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About a year ago, when the BE tweeters first appeared in the Reference 3A lineup, I wrote to Tash Goka, head of Reference 3A, about upgrading my De Capo's to the new tweeter, and questioned him about the reputation of metal dome tweeters for harshness. Here's what he wrote back:

"Opinions about the "harsh sound" metal domes propagates may generally be true although some loudspeakers have used them successfully in the past.
They were usually made with aluminum, magnesium or titanium, etc...
This ringing metallic sound was also our finding whenever we have tried them for a project.
Metallurgy of Beryllium is different however. It is significantly lighter, stronger and definitely more inert. Sonically it is very bwell balanced, detailed, and spacious due to extended higher frequencies well in to 40 kHz range."
Was checking out Beryllium tweeters by Seas and Scanspeak, they retail around $500 each.