Personally, I have not noticed a difference with most of my Axioms. The exception was the M2. When I was using them as computer speakers I could not stand the highs with the grills off. These were the only set I had that I could see being described as "ear bleedingly bright", although that is a bit of hyperbole. I found that the grills tamed the highs fairly nicely.
I find it interesting that you would notice a large difference with the M2's, but not the others. Does Axiom use different grill fabric on the different models? That would be the only reason I can think of why there would be such a contrast to the sound of the speakers.
