That's a good review Oz, very thorough.
The post on sibilance was a subject still under discussion, but the long and short is that the speakers don't make the sibilance. That comes from the recording.
A speaker could make a bright sound, if it had peaks in the upper frequency ranges. The recording could also be bright, if it were mixed with a bumped treble.
I do find the Axioms to be forward in their presentation. I have never found them to be sibilant.
I recently tested, in A/B blind format, the M40, M60 and some Tannoy Definitions D700s to review these ideas, and will post the last results later in
the thread.
The M60s are an excellent speaker for their price, but they are certainly not the only speaker of quality out there. The rest of your expected auditions should prove to be interesting. The A/B switcher i recently borrowed has been extremely helpful in elucidating the difference in sound character b/w speakers without having to rely on audio memory (notablly unreliable method).
