Hi Hologram. Can't comment on the M1. I have the M3, M2 and Mzero.
The M2's midrange does not seem to be recessed, as is the case with the M3 (slight recess). The M2 also has a lighter mid-bass presentation than the M3. It may be that the M2 is slightly more balanced than the M3, however, I prefer the presentation of the M3. It is an exceptional speaker that sounds wonderful even without augmenting it with a sub. It can also play louder than the M2 before congestion sets in.
The Mzeros sound almost as good as the M3's in terms of its sonic presentation, however, only in respect to listening near-field. It cannot fill out a small room like the larger Axiom monitors can; and remains largely devoid of any significant low bass information. Works very well with a sub, but the crossover has to be set higher, which may make seamless integration with a sub a little troublesome.
Very happy with all my Axiom speakers (and that includes also my AX-1 monitors, AX-1 Center, AX-3 towers and AX-500a subs).
