Quadraphonic sound system

In multiple channel stereo system, the reproduction will be more natural when we include reflections from the back wall which usually occur in natural environment. This is achieved by using four channels for recording and reproduction. This technique is known as Quadraphonic sound system or quad system. Here two extra microphones are employed to pick up the reflection from the rear wall while recording. During reproduction, two extra loudspeakers are placed behind the listener in the corners of the listening room to imitate the actual conditions in the concert hall. This system failed to become popular due to lack of compatibility with the two channel stereo system.