Hi everyone!
Good and bad news at once.
The non working diamond tweeter is changed now and the speaker is back in perfect shape, shininig with crisp highs
The other speaker, which I thought has some king of problem with the high frequencies is now confirmed to be a problem
! With test track which has not more than 3-3.5kHz the tweeter is making some rustling noise. The HF filter should cut everything below 4kHz. Previously i was not sure if the ears or the room acoustic is playing with me but now with isolated track it's obvious the filter is the problem.
The other speaker tweeter is in absolute silence with this track at every amp volume level. Swapped the channels to be absolutely sure and yes the problem is in the same speaker.
Got the track played on other 3way speakers - there is no sound from the tweeters there.
I am very dissapointed from the quality control in B&W nowdays. Not mentioning the waiting time for repair. The speakers are brand new - produced in Dec 2020 , delivered in Feb 2021 to me.