Beryllium Tweets

There's also a beryllium ribbon tweeter. First introduced in the early 1980's by Pioneer, designed by their TAD division. Frequency range up to 100.000Hz!

It was available in some top end speaker models like S-955 and S-933, but also as an add-on unit (PT-R7 and updated version PT-R9).

I don't think it is still being made, but they do appear on the used market from time to time. Not exactly cheap, but highly recommended!

Depends on the implementation and the tweeter - I have heard some dreadful beryllium tweeters that are so metallic sounding I want to take an ice pick to my ears.  These will remain unnamed.  

Other sound spectacular.  Tons of detail and wonderful imaging.  I like Magicos sound a lot and think they have one of the best Beryllium implementations. 

Incidentally, you could write the same post about AMTs today which are suddenly hot and could have written it in the past about diamond tweeters, silk domes, other metal domes, etc...

There is good and bad. I opted against beryllium partially because I did find the ones I tried a little metallic sounding but I also like to do something a little different and am super happy with the ceramic magnesiums I have in my speakers.   

Yep, a broad-brush assessment is worthless about much of audio technology.  It all gets down to the implementation, whether it's with BE or silk.  Silly to float float praise or condemnation broadly.  It is only meaningful in specifics.

Metal dome tweeters all have a high propensity to ring at high frequencies.( the old Focal titanium dome that was used in Wilson speakers was one of the worst offenders). Some folks are lucky enough not to hear this, unfortunately, I am not one of those people. Most ( say 90%+) of the Beryllium drivers I have heard can get bright and unpleasant to my ears, OTOH a silk dome or a ribbon seems to not have these issues. One of the best tweeters I have heard recently is the new YG silk/metal dome...seems to have the best of both worlds.