Guess what? The matching QS-8 has developped the same issue (hyper vibrating top driver).

I swapped with the drvier from my spare M22 and it stopped.
BUT, I could feel the whole speaker was strained (whole QS-8 cabinet shaking too much for a speaker).

I was using a xover of 80z. I uploaded a new one at 115hz (the recommended xover by Anthem's ARC measurements) and the speaker is no longer strained.

Should receive an answer from Axiom soon. In the meantime I'll if I can notice the xover shift. Maybe I'll it better!

See Mojo's signature