As dweller said/implied - your speaker orientation has the biggest impact in your overall sound. One should always try orient your speakers along the long axis of the room. Sometimes that isn't possible (The CFO booted me out of my former room into a 'larger' 12' by 12' space. That being said, if you are already going along the long wall, have you tried to change the angle of the sub? I have my Infinity BU-1 firing into the corner of my room behind my Infinity 6 Kappa speakers. With sub woofers, there is a lot of trial and error. A lot!
If you have a favorite CD recording, one that you know particularly well, count on playing it a few times, especially on low-end heavy portions to dial in your sub-woofer position.
If you have a favorite CD recording, one that you know particularly well, count on playing it a few times, especially on low-end heavy portions to dial in your sub-woofer position.