"Constructive and Destructive Interference." What happens when two speakers of a stereo are brought face to face? Why? How does the placement of your home stereo system affect the sound quality in the room?
If two speakers are brought face to face with no separation, then they will be out of phase with each other and the sound will be cancelled out. Placement of the speakers in your home theater setup will directly affect locations where you get constructive and destructive interference. There will be locations where the sound is out of phase and locations where it is in phase. This can be easily observed by having two speakers playing a tone facing the same direction toward the listener, and moving forward and backward on the axis of symmetry between them. There will be observed changes in volume. The interference patterns get more complicated with more sound sources and their respective placements.