An introduction to the next generation cinema sound format based on Dolby Digital, now finding its way onto high-end home cinema amplifiers.
INTRODUCTION
MONO
STEREO
QUAD
DOLBY STEREO
DOLBY SURROUND
DOLBY PRO-LOGIC
DOLBY DIGITAL
DOLBY DIGITAL-EX
DTS
DTS-ES
MPEG-II
SONY SDDS
THX
TIMELINE

Sound Formats

 

Dolby Digital EX  

 

 

DOLBY DIGITAL SURROUND-EX

The next generation of digital surround sound is based on the Dolby Digital 5.1 format. Jointly developed by Dolby Laboratories and Lucasfilm, the Surround EX standard adds an additional rear surround channel composed of a matrixed combination of the rear-surround left and rear-surround right channels. In practice, this means that the existing rear surround speakers (known as surround-left and surround-right) will be positioned to the sides of the theatre, with the new channel (known as surround-back) played back through two or more speakers mounted on the rear wall. This will create a more realistic sound stage around the listener, adding scope for impressive effects and allowing sounds to move across the rear soundstage in a more realistic movement. The first movie to be encoded with EX was the Lucasfilm release Star Wars: Episode 1 - The Phantom Menace on May 21st 1999, followed shortly after by the second adventure with Austin Powers.

The home cinema version of Surround-EX is now available as an option on some high-end THX Ultra amplifiers, and is referred to as THX Surround-EX. These amplifiers contain the additional decoding that is needed to extract the additional sound information from the two rear surround channels. Because the surround-back audio information in matrixed within surround-left and surround-right channels, an EX encoded soundtrack will replay as a normal 5.1 channel soundtrack on any Dolby Digital system where the EX decoding is not present. In this situation, the surround-back information is distributed between the other rear surround channels, in a similar way to how the centre channel of a Dolby Surround soundtrack is divided between the two front speakers when a centre speaker is not used.