John,

The reason I nudge buyers away from Yamaha A/V receivers if they are considering the 4-0hm M80s is that we've had the occasional Axiom customer who has gotten the 4-ohm M80s and their Yamaha goes into an apparent current-limiting mode, with low power output and audible distortion.

Those symptoms suggest the protection circuitry is severely limiting power output into low impedances. I don't know the specifics of the Yamaha 1400, but the engineering of the unit would have to have changed, which I doubt.

Regards,

Alan Lofft,
Axiom Resident Expert (Retired)