What are the differences in Tweeter materials?

To my point of view à tweeter that does not have à contribution to the mid-driver can not realy help the speaker to breath.the only one the answered the need in the case of my speakers talon khorus II was AUDAS titanium

"Just a general observation: I've heard plenty of metal-dome tweeters that sound the way soft domes are reputed to sound, and I've heard plenty of soft-domed tweeters that sound the way metal domes are reputed to sound. I don't think you can make generalizations about the sound character of one or the other.
-Bob"

Very interesting post. I understand what you are saying but can you give some examples? For me, getting the high frequencies right, is one of my most important goals when setting up a system. Overall, I tend to prefer non metal tweeters. If you've found some exceptions to how metal tweeters typically sound, I'd really like to check them out myself. So far, I've never heard a metal tweeter that goes that far as to sound like a soft dome.

.. Then there is heil type folded diaphragm type still used in some speakers like goldenear. I've always thought these to have some unique advantages though I have also observed these as somewhat delicate and not hard to fry in years past. I heard a pair of goldenear aon speakers just today. Very smooth and easy on the ear with good detail. Had not heard a heil type tweet in years.

"Very interesting post. I understand what you are saying but can you give some examples?"

Offhand, I'd say that Harbeth and Totem both use metal tweeters that, to my ears, have none of the harsh, shrill metallic sound many people seem to associate with metal tweeters. As for soft domes, I've had some Spendor 3/1Ps and Vienna Haydns that, while not really exhibiting the shrillness people often associate with metal domes, had a certain hard, cold quality people don't usually associate with soft domes. (By the way, when I said I'd heard "plenty" of examples of both, I may have fallen victim to my own rhetorical devices; I should have just said that I've heard examples of both.)

A well designed tweeter of any material should never sound shrill or harsh. Again, whether you like the term "in general" or not, proper damping controls the rise and dips in any material and tweeter material in itself is not the deciding factor, but every material has a resonance and a ringing frequency, it is how well those peaks and dips are controlled and at what frequency that tell the whole story.