Today's emphasis on home theater surround sound requires new audio formats, receivers, and more speakers to produce the movie theater experience at home. One of the most significant changes in the transition from stereo to home theater surround sound is the need for a dedicated center channel speaker.
Do you REALLY need a center channel??!
Stereo audio was originally designed to separate recorded sound into two channels (that's what the term "stereo" means), with left and right channel speakers placed in front of the room. While some sounds come specifically from the left or right channel speakers, main vocals or dialogue are mixed across both speakers.
With the vocals mixed to come from both the left and right channels, a "sweet spot" is created that is equally distant between the left and right channel speakers. This gives the listener the illusion that the vocals are coming from a ghostly center spot between the left and right channel speakers.
While this is an effective way to present vocals, the position of the vocals will (or should) move with you as you move your listening position from the sweet spot to the left or right. The left and right sounds will remain in their relative positions determined by the left and right channel speakers.
