The sofa is not the cause. If it is sitting in a null, moving it will not help but I have yet to find a sofa which is such a good bass absorber as to create a null.
Getting the listening position off the back wall and repositioning the speakers is important as is the use of true bass traps (at the intersections of room boundaries) to reduce both nodes and nulls.
Kal
Getting the listening position off the back wall and repositioning the speakers is important as is the use of true bass traps (at the intersections of room boundaries) to reduce both nodes and nulls.
Kal