Dolby Digital EX is actually based on the technology already developed for Dolby
Digital 5.1. This process adds a third surround channel that is placed directly
behind the listener.
In other words, the listener has both a front centre channel and, with Dolby Digital
EX, a rear centre channel. If you are losing count, the channels are labelled: Left
Front, Centre, Right Front, Surround Left, Surround Right, Subwoofer, with a Surround
Back Centre (6.1) or Surround Back Left and Surround Back Right (which would actually
be a single channel - in terms of Dolby Digital EX decoding). This obviously requires
another amplifier and a special decoder in the A/V Surround Receiver.
The Benefits Of Dolby Digital EX
So, what is the benefit of the EX enhancement to Dolby Digital Surround Sound? Essentially,
it boils down to this: In Dolby Digital, much of the surround sound effects move
towards the listener from the front or sides. However, the sound loses some directionality
as it moves along the sides to the rear, making a precise directional sense of sounds
from moving objects moving or panning across the room difficult. By placing a new
channel directly behind the listener, panning and positioning of sounds emanating
from the sides to the rear are much more precise. Also, with the additional rear
channel, it is possible to originate sounds and effects from the rear more precisely
as well. This places the listener even more in the centre of the action.
Dolby Digital EX Compatibility
Dolby Digital EX is completely compatible with Dolby Digital 5.1. Since the Surround
EX signals are matrixed within the Dolby Digital 5.1 signal, software titles encoded
with EX can still be played on existing DVD players with Dolby Digital outputs and
decoded in 5.1 on existing Dolby Digital Receivers.
Although you may end up buying new EX-encoded versions of films you may have already
in your collection when you finally get your EX setup running, you can still play
your current DVDs through a 6.1 Channel Receiver and you will be able to play your
new EX-encoded discs through a 5.1 channel receiver, which will just retain the
additional information with the current 5.1 surround scheme.