I used to have my couch in a bass null. I know what you mean.
And you fixed it by...?
I tried repositioning them a dozen times... to no avail. Some interesting facts:
It sounds like you have a bass null at the listening position. Nulls are created when sound waves reflecting off room surfaces cancel each other out. I have a few questions:
When you say you tried repositioning, how much have you moved the speakers around? Sometimes changing the distance from the back and/or side walls can change the timing and eliminate a null. Sometimes not. For instance, I have a null at around 72 Hz that is there no matter where I put my sub and speakers. Fortunately it is very narrow, so not very audible.
What shape is your room? Square is not good as it tends to replicate room modes that cause peaks and nulls. Again, I had a giant 16 db peak at 56 Hz, precisely because my apartment is essentially square. Fortunately, peaks can be dealt with by equalization.
Somewhere in the article section on the Axiom site on a simple method of finding the best place for your sub. It involves putting your sub at the listening position and crawling about the room to find where the bass sounds the best. That is then where you put the sub. I wonder if you can do something similar with one of your M80s?
If you are technically inclined and somewhat obsessive, you can try to measure your speaker response using software called REW and an spl meter to see what's really going on.
Lastly, you can always drastically rearrange you room based on where you get the best sound.
Hopefully that gives you a bit to think about.
