Hello lucv13,
The early M60ti was kind of sibilant and harsh on female vocals and brass instruments. In double-blind tests when I worked for Axiom, I did not like them.
Later versions of the M60s got much smoother and better; in fact, before I retired from Axiom, I can recall a comment I made in double-blind listening tests at the factory: "This is a wonderful speaker."
I don't know which version of the M60 was involved in the tests, but it's been a few years since I retired, so it was likely the v3 or v4. Ian would have the listening test records on file somewhere in his office.
Regards,
Alan Lofft
