The problem isn't from the subwoofer ( i bet ) Because i still got this weird sound comming from the center channel even if i have the subwoofer cable unplug. I actually can use 1 or 2 channel for my subwoofer and like i said from my level calibration the sound comming from the center channel.
Big HT receivers can get pretty complicated. But right now, i am completly confuse.

Nad C356 DAC & C515
Axiom M3v3
Grant Fidelity RPF-120 MKII
Analysis Plus Black Oval 12&10
JRiver 19