There is a common misconception being perpetrated here.
The reflected acoustics off the side walls are NOT out of phase and will not destroy stereo image provided the speakers are an equal distance from the side walls and the listener is sitting in the middle with ear level at the height of the mid range.
Although the reflected sound will not be in phase with the primary signal reaching your ears directly from the speakers, the reflected sound off each wall will be in phase with that from the opposite wall and therefore still present a stereo image that allows you to pinpoint the sound position source between the speakers.
The critical factor is to ensure that the reverberant field has enough delay relative to the direct sound so that your brain can distinguish it from the direct energy....i.e. do NOT place the speakers right up against the side walls as the reverberant field becomes completely mixed up with the primary field and the brain can't figure it all out resulting in a poor stereo image...
I find that placing the speakers three feet away from side walls is a safe distance.
The reflected acoustics off the side walls are NOT out of phase and will not destroy stereo image provided the speakers are an equal distance from the side walls and the listener is sitting in the middle with ear level at the height of the mid range.
Although the reflected sound will not be in phase with the primary signal reaching your ears directly from the speakers, the reflected sound off each wall will be in phase with that from the opposite wall and therefore still present a stereo image that allows you to pinpoint the sound position source between the speakers.
The critical factor is to ensure that the reverberant field has enough delay relative to the direct sound so that your brain can distinguish it from the direct energy....i.e. do NOT place the speakers right up against the side walls as the reverberant field becomes completely mixed up with the primary field and the brain can't figure it all out resulting in a poor stereo image...
I find that placing the speakers three feet away from side walls is a safe distance.