What Ken said.
The speakers are just revealing more short comings when the volume is turned up. This is a trait I have exclaimed about the M60. It sounds more like the M80s when the volume is increased but when the volume is low the M60 is reasonably laid back and poor recordings are acceptable on them.
I recently listened to a set of Monitor Audio speakers. On my M80s and many other speakers Dianna Krall has a very noticeable sibilance on her discs. On the Monitor Audio RX-8(?) she had no sibilance what so ever, but to me this made her seem lifeless. The highs were subdued, yet still there, not very lifelike IMO. I commented on this to the salesman and he agreed and mentioned how he wished they wouldn't overdrive everything live and then said I need to listen to the gold series much more open and lifelike as I was describing.
Different speakers for different sound preferences.
