Sorry for double posting, but i noticed in the FR charts for the M22, M60 and to a lesser extent the M80, the treble response starts dropping quite drastically at about 16kHz and is -10dB by 20kHz.

Is this physically audible? How does it compare with speakers that have flat response up to 25kHz or even 40kHz? I would imagine it being described a 'airy'. After all, most people can't really hear 20kHz.