Being a small room, and *square* having an 11 X 11 footprint, you're going to have a LOT of bass problems. Play some bass heavy music, and walk around your room - I'm betting you'll have these bass heavy spots, and absolute bass suck points. In order to start correcting your issues, you need to get rid of some of that bass!
Sounds counter-intuitive, I know. But what's happening is those giant 20'+ bass waves are slamming into each other as they are trying to stretch out in your room. So one wave might bounce back and fourth between your walls multiple times before the full wave is even developed!
Think about it like this. You have a positive wave that hits a wall and bounces back and runs into itself. If it happens to bump into itself at another positive wave, you get a BIG muddy boom at that spot. If the positive wave happens to hit on a negative wave of itself, it cancels itself out and you have a suck spot - it's like being in the eye of a tornado everything is weirdly dead but theirs sound all around you.
So what you do is throw up big bass traps in the corners - the bass traps soak up a bunch of that excess bass so the bounce doesn't + or - itself. You still hear the main note, but the bounces are less damaging. There is almost no way to really deal with big bass in a small room. It's never going to be right - but you can do your best to lessen the damage.
It's not light reading - but do some googling on Superchunk bass traps. It's the colloquial name for the big corner traps of which I speak.
http://arqen.com/bass-traps-101/placement-guide/If you put diffusion between the speakers on the front wall, you have a chance of deepening and sharpening your soundstage. But being in a smaller room, and square to boot, I think you're going to need several acoustic absorbers.