John is right with respect to the room-boundary effects on bass reproduction. However, there is a separate, equally pertinent issue of the adverse effects by the early reflection from the front and side walls. The early-reflected sound in midrange and treble frequencies from the walls nearby the speakers can color the timbre and negatively impact imaging and soundstaging.

The easiest solution is to place the speakers as far as possible from the front/side walls -- that will result in more time delays of the wall-reflected sound compared to direct sound reaching from the speaker to your ears. The reflected sound will simply have to travel further if the speakers are placed further from all walls. Larger time delays on reflected sound will have a significant impact on the auditory processing in your brain. Your brain is evolutionarily programmed to unconsciously focus on the sound that reaches your ears first. With larger time delays on reflected sound, your brain can use this "precedence effect," reducing the adverse effects of early-reflected sound coming from the front/side walls.