I wonder how many beryllium drivers you could find for diy. Beryllium isn't real friendly stuff, so I imagine that there might be some hesitancy to sell to the diy crowd.

That said, years ago, there was a controversy with Usher speakers and whether they really used beryllium in their speakers drivers, suggesting that the material used was barely beryllium and that its as much marketing as it is, sonic performance.

I really don't know, just that I wouldn't get too hung up on it being beryllium.

Primary: MD600, MS200 (SpeakerLink to AES), Trinnov ST-2, Ayre V6-xe, Salk SS8 3x LRC.
Secondary: MC600 (whole house).
Zone one: 568.2, G57, MS200, Spatial Hologram M2SE.
Zone 2-6 (Awaiting assignment).