Originally Posted by
Lerxst
Yeah, usually it is the worst thing to control. Does it increase and decrease as you move round the room? Pointing the speakers in a different direction doesn't help (just make things asymmetrical)? A little bit further away from the wall to mess up the reflections a bit. What shape is the room? Sounds like some kind of cancellation effect. There are some frequency generators on the internet - you may have a problem with a certain frequency range and something that is absorbing in that range.
I am afraid I am probably suggesting things you have already done. Given the choice I would have the speakers at the long end of the room and listen about 2/3 of the length of the room. So, speakers pointing along the length, not width.