So why does Axiom and other manufacturers talk about cascading (I believe that is the term) conflicts when having the sub crossover not on bypass or turned up to the highest setting whe your AVR is handling the bass management?
I need a better description to what it is you are referring.
If a subwoofer overlaps frequencies of the main speakers you would have an overlap of bass.
That is a given.
But the main speakers begin to naturally roll off in SPL (what you see on the frequency graph) and the subwoofer can take up the SPL from that point (or somewhere around that point, preference goes to the user and of course room will play a role here as well).
The subwoofer internal x-over must be set to match that preferred roll off point (too high and you have bass overlap, too low and you have a bass hole) and the sub volume needs to be adjusted to match the base SPL of the mains.
The AVR has nothing to do with this situation if its x-over is essentially turned off and the mains and sub allowed to play full range together. It is the subwoofer x-over knob that becomes the master controlling point.
All the AVR x-over setting does is make that roll off point at 80Hz and begin the mains rolloff at that Hz.
There is no difference in using the natural low end rolloff of the mains to do that very same thing except that the mains will play to a lower point and the sub picks up SPL at a lower point.
Hell, some AVRs even have lower x-over settings below 80 now. If i had an AVR with an internal x-over of 40Hz, it would actually be too low for the M60s!!
