Its a valid criticism by Gene and you have to take into consideration the conditions the possible impedance and break-up/distortion issues would occur. The M60's ran full range, low/heavy bass content and loud volumes. Those were the conditions from what I read. He also noted he shut down a 200wpc Marantz with the M60's under similar conditions. Probably more in the realm of a torture test than that of real-world listening conditions.
Personally, I don't think this would be a problem in most scenarios. The majority of people use a subwoofer with the M60's set to small and use a 60hz or 80hz crossover and let the sub do the rest. I don't think I have ever read complaints of the M60 breaking up either.
This is obviously purposely done by Axiom. Since it changes the upper bass output, it was probably desired in their listening tests they conduct. As we all know Axiom does a lot of unconventional things most speaker designers would not do. There is no wrong or right. Its all about the trade-offs and what they seek in the design.
