Okay, biwire, so the straps on the terminals aren't used. Assume you also checked Mike's point about the wiring polarity, so more unlikely possibilities: are you sure both M80s are affected, because if not, remotely possible that one M80 woofer wired wrong internally or one of your speaker cables to a woofer is bad(check that by replacing the straps so that at least one cable would be feeding the woofer). Next, did you actually turn off the SVS by setting no sub in the 7200 rather than just turning the sub volume all the way down? If just the volume, the SVS would still get the bass at the "small" setting, but it wouldn't be heard. To be continued.
