Dolby and DTS Sound Formats

Dolby Surround Four channels of information - Front Left, Center, Front Right, and Rear Surround into a two channel signal. A decoding chip then decodes the four channels and sends them to the appropriate destination, the Left, Right, Rear, and Phantom Center (center channel is derived from the L/R front channels). The result is a more balanced listening environment in which the main sounds derive from the left and right channels, the vocal or dialog emanates from the center phantom channel, and the ambience or effects information comes in from behind the listener.

Dolby Pro Logic The absolute minimum standard for all home cinema systems. All films have been made in Dolby Prologic for many years so there is a vast amount of material to be watched (and listened to). The Prologic soundtrack is originally produced in the studio and mixed into five channels. This is how it is shown in the cinema. When a film is transferred onto a video format the soundtrack on the video is stereo ie. two channels. Now for the clever part: The five Prologic channels of sound are hidden (encoded) within the stereo soundtrack. They are not apparent unless special equipment is used to extract the five channels from the stereo soundtrack. These channels consist of the main stereo left and right pair, the centre channel and the rear channel which is two speakers wired in mono. There is also a facility for a subwoofer output. This channel handles the real low frequency bass sounds and is optional.

Dolby Digital Dolby Digital is essentially similar to Dolby Prologic. The main difference is that with the Dolby Digital format all the encoding and decoding is done by digital electronics. This makes for an even more exciting ride than straight Prologic with an added bonus that the two rear channels are in stereo. Also, the bandwidth is far wider on the speakers. This makes an incredible difference to the soundstage. Dolby Digital requires a digital sound source such as DVD, Satellite, Digital TV but also handles the straight Prologic signals without any hassle. In short, if you are buying a Home Cinema reciever or processor, make sure it is Dolby Digital ready (must carry the Dolby Digital logo on its front panel). Even though you will only be listening to straight Prologic to start with, before too long you can be certain that you will become involved with Dolby Digital.

Digital Theater Systems (DTS) A 5.1 system just like Dolby Digital, but since DTS uses less compression in encoding process, many feel that DTS has a better result on the listening end. In addition, while Dolby Digital is mainly intended for the Movie Soundtrack experience, DTS is being used in the mixing and reproduction of Musical performances. Many CD-only players now come equipped with DTS outputs that allow a DTS-equipped amplifier or receiver to decode the DTS signals imprinted on "select" DTS-encoded music CD's.