Which tweeter is the best, one used by B&W, the other used by Focal Usher, but is one better than the other?

The B&W 800Diamond are dream speakers, that treble is just luscious.

Let me see...which car is the best, the Ferrari or the Lamborghini? They're both good and both have their respective weaknesses compared to each other. You talk to the Focal folks andthey'll give you loads of reasons why Beryllium is better. e.g. You can make a thinner, lighter diaphragm, you can control the resonances more easily. B&W will turn round and say things like, beryllium is poisonous and a genuine health hazard should the diaphragm be broken, the diamond diaphragm is stiffer.

And in the end it's all down to implementation anyway. You might have the best tweeter in the world but put it into a poorly designed box attached to poorly chosen components and a mess is the result. True, Focal and B&W should know what they're doing, but even so, what if you don't like the B&W presentation, or for that matter the Focal's? In that case, it doesn't matter which is better on paper. The one that counts for you is the one you like.

And I don't see SEAS making either beryllium or diamond tweeters, yet they're drive unit specialists of the first order! Their most exotic tweeter uses magnesium. (OK, SCAN make a beryllium tweeter...)

A good answer that frank, it's not so much the technology, though for sure it plays it's part, but the implementation.

My Kudos C30 use the SEAS cresendos and it's a very sweet, detailed treble unit, I believe Art use the same tweeter and I've seen comments saying it's bright and sharp, I don't get it because that's not what I hear, as always listen to decide which is best for you, your room, source and cabling.

Diamond is definitely better than beryllium - if only cos it's not so b***** horrible a substance! I'd rather not be responsible for anyone having to work with beryllium when it's not absolutely necessary.

Well so long as you don't break the thing, you're OK. It's only intensely carcenogenic in powder form, but I get what you're saying Richard!

And as you say, magnesium is a safe alternative and almost as light - or titanium perhaps, although that's harder to work...

Titanium tweeters - I'm sure I've come across some of those, though I can't think where. Don't recall magnesium ones but I'd be surprised if someone hasn't done it. But then soft domes can work pretty well too. My experience definitely supports the 'it ain't what you got....' school of thought!

SEAS make one...