The brightness/harshness is most often minor distortion caused by the electronics and mistakenly blamed on the speaker.
I have an emotiva ERM 6.3 that I use as a center. It is a 3 way design but only 26 inches tall so can be used as a (tall) standmount as well as center. Since I was having trouble with the brightness on some music I connected the ERM 6.3 as the left speaker and the M60 as right speaker, put the preamp on mono so the same sound would come out of both and cranked it. The erm 6.3 just doesn't have the same brightness. Now the 6.3 has compensation switches on the back but I've set them for the "brightest" setting (not engaged) to ensure I wasn't hearing a speaker that was attentuating the highs. I was really hoping to be able to "tame" the brightness that occurs on some music because a lot of my music sounds great on the M60s. One of the differences in the 2 speakers is the tweeter on the 6.3 is a silk dome as opposed to titanium tweeters on the axioms. I've started obtaining high res music now (96kHz/24 bit) and am starting to get quite a few titles. Those are master studio quality, much better than CD redbook (44.1kHz/16 bit) so my hope was to be able to listen to them without having to process/filter anything out.
