When I first got my M22s (initially without a sub) I thought they were a little bright. After integrating the STF-2 sub, they didn't seem so bright. When I moved up to M60s, I mostly didn't notice the brightness. A few recordings are exceptions and still seem bright.
As already mentioned, another possibility is room-related brightness. After using the parametric equalizer on my Yamaha RX-V1400, some recordings that sounded bright just sound normal.
So the idea makes sense that Axiom speakers are merely accurate and most "brightness" is source or room related.
