Dolby Surround Sound has been in existence since the 1960's. The normal stereo channels of the film or music, are given an inaudible high frequency signal which divide the signals still further into four or more channels with some clever audio processing. As processing power is very cheap these days, even the average television has surround sound capability.
     With Surround Sound, the left and right speakers are placed in front of the listener, and two additional rear left and rear right speakers are placed behind. This is the most simple implementation of Surround Sound, using only four speakers. The intention is to force a large 3D soundscape, where sounds and noises from the film appear to be extremely directional.
     Additional enhancements to the surround sound principle include a dialogue speaker behind or below the screen. The hardware of the speaker for this function would be selected deliberately toward a strong mid range for speech clarity. It would be a powerful mono system with no extended bass or treble ranges.
     The finishing touch to Surround sound would be the Bass Bins, which would be placed ideally, in a chamber under the auditorium seats. These would be very powerfully driven but kept at low gain to add rumbles and atmosphere to the film.

DTS 6 Track
With this system the normal stereo soundtrack on the film incorporates a synchronizing clock signal. This signal can be used to time - lock synchronize a special format digital C.D. which contains all 6 tracks. The C.D. plays the sound of the movie through a separate sound player with complete digital clarity, ignoring the basic stereo soundtrack on the film altogether.
     If the system goes wrong though, or the cinema doesn't have the equipment, then the normal stereo track, on the film, can be used as backup.