Advantages of beryllium?

@erik_squires 
It's not so much as just a lack of necessity. The voice coils in the inverted domes are way smaller than anything you'll ever see in a convex dome even 3/4ths the size. You just don't need a magnet as large to concentrate the same energy in the smaller coil. 
And yes, the 936 uses an Al-Mg tweeter. I think I mentioned that. My point was to dispell the myths and dogma some like to generically attribute to metal drivers. 

Micro-motor tweeters are just tweeters with the bare minimum motors to work. Focal as well as B&W are proponents of this approach. The motor is no wider than the dome and usually less than half an inch thick.

Despite assertions otherwise, popular micro-motors measure terribly across distortion, frequency and lack of linearity, regardless of material used.

They are routinely outclassed by relatively inexpensive models from popular driver vendors.

Best,

E

@erik_squires 
I'm gonna ask you to prove that jazz. 

Does seem one poster has no idea what a TAD driver is  http://www.technicalaudiodevices.com/pro-hf-units/  and he seems to suggest vintage doesn't perform as well as modern I suggest he point me towards a BE equipped modern driver with better specs than a TAD?