Chances are if you get the same sound with the new driver it may not be the speaker. If you are really unsure about this then return the speaker to Axiom so they can test it themselves. If the speaker proves faulty, i'm almost positive they will send you out a brand new unit.
Axiom customer service and their policies with customers problems have been absolutely stellar so far in my experience. I personally believe that Axiom also produces some of the highest quality speakers for their price range. A good friend of mine who does electronics and speaker repairs for a living (and who has seen those crazy $100, 000 speaker systems) commented the other day on the nice Vifa tweeters in the M22s. If anyone can corroborate that observation i would really like to know.
All these people on the forums would not be here if Axiom was not a quality company.

Just offhand though, your problem does not sound like my own. The buzz in my speaker is definitely mechanical in nature directly related to 2 of the 6 inch woofers. It is best described as the woofer vibrating against something right behind it in the driver basket which occurs at a certain range of low frequency sounds. The 2 other 6 inch woofers on my M60s do NOT make this sound hence i can only assume i have 2 defective drivers.
Axiom is sending me replacements. No other M60 owners have yet found this problem although something similar was mentioned about center channels which is what precipitated this thread.

"Those who preach the myths of audio are ignorant of truth."