There have been older posts in other threads that compared BE dome tweeters to other types of dome tweeters. My general recollection is that BE dome tweeters are much stiffer and lighter than most other (if not all) types of dome tweeter materials on the market. Of course, I am not speaking about ribbons or stats.
That said, IMO, there is more to the "quals" of a dynamic "box" speaker than just the tweeter. In particular, the start/stop speed and resonance point of a dome tweeter are not the only specs that count.
As to BE being toxic, ... yes I have read the same thing, but I gather that BE toxicity has more to do with the manufacturing process when BE may be in an aerosol or particulate state. Once it's formed into a final dome shape and mounted in the tweeter housing, I surmise that it's pretty harmless in that inert state.
FWIW, my Paradigm Signature 8(v3) speakers use BE tweeters. So I have a little background here. As an additional FYI, Magico and Focal also use BE tweeters. But going to my point above about overall speaker "quals," Paradigm, Magico and Focals employ many different manufacturing and technology approaches that make them sound differently from each other.
Not much more to say about this very narrow question. In the end, its all about how a particular good quality speaker matches up with one's amp and how the over-all combo of everything sounds in the listener's room. It has taken me years of mixing and matching stuff and I'm still not done.
One of my pet and not favorite irks is my bloody room. Neither BE nor diamonds will fix that problem. Think DEQX.
