Good point.
As someone that worked with sound and lighting for about 10 years with local musicians, I use the same criteria that the musicians use during sound check.
Listen to the snare drum. Does it sound sharp, crisp, and not tinny. Then listen to each tom (drum) for nice, short controlled thumps of the proper tone with no ringing or dull sound. Then the kick drum. It should be a very solid, dull, but powerful thmump. Cymbals should sound bright as hell, especially when nothing else is playing. ANY music with a lot of cymbals in it should be very bright. Stand within 2 feet of one when a pro bashes it and tell me it's not bright. Phooey on you, I say...
Then I just listen to each instrument at a time, checking to see that it sounds just right. It's easy to do once you get the hang of it. Look at the CD case to get the # of musicians, and the type of instruments that they play if you don't know the band. Concentrate on each instrument as you listen. If I find that the bass sounds muddy or too low in volume, I move the speaker a bit away from or closer to the wall to fix it. Eventually, you'll find a spot where all of the instruments sound correct in their own right. Of course, none of this is specific to rock music, so I can say that a good speaker should be able to play all types of music well.
The one thing that a good "rock" speaker needs is the ability to play loud. The M60s have a point where once you feed them a certain amount of power they just really liven up and seem to demand more. The more power I feed them, the better they sound. Unbelieveable. I ran out of power way before I ran out of speaker...
I'm going to peform the absolute test of a speaker. I have a friend,
Ben who has a few VERY nice CDs out now. (Yes, that was a plug - the man is a great guitar player - buy one of his CDs - I'll call him to let him know the MP3 links are dead...). I'm going to invite him over to listen to his own CDs on my Axiom setup. I've heard him play live a hundred times. Indoors, outdoors, acoustic, electric, and on his own stereo at his house as well. I can tell you for sure that MY setup sounds
exactly like he does live. Amie better write that $20 check to me now, because I KNOW Ben will be buying some M60s soon. At any rate, he is also on a few harder rock CDs from a few other bands as a "hired" guitar, so we'll have some other stuff he knows as well. His own stuff is very jazz / classical oriented guitar. The ultimate test would be to have him plug his guitar into my AVR and have him whip out his PERFECT rendition of the White Cliffs of Dover through my Axioms. He plays it better than Eric Johnson himself... I'll let you guys know what he thinks after he listens to "First Light" over here.