Dolby Digital 6.1 EX is an enhancement
to the standard Dolby Digital setup provided in most theatres. Concieved by Oscar-winning sound designer Gary Rydstrom
and with joint collaberation with THX and Dolby Laboratories
, the addition of a "back" channel to the theatre seemed a logical step in the evolution of theatre digital sound
Although Dolby 5.1 is a complete discrete 5 channel and LFE setup, Dolby 6.1EX is not. The additional "back" channel is derived from the matrixed components of the left and right surround channels.
Since DD6.1EX is a technology that is a subclass of DD5.1, then all DD6.1EX films are playable through a DD5.1 decoder.
Debuted in the latest chapter of the Star Wars series : Episode I, the new technology was also used in the following movies.
Toy Story 2
Mission to Mars
James Bond: The World Is Not Enough®
New Line Cinema
Austin Powers: The Spy Who Shagged Me
The Messenger: The Joan of Arc Story
Twentieth Century Fox
The Fight Club
Star Wars, Episode One
The Bone Collector
The list of films using this was taken from the Dolby website. (quite some time ago, may I add.)