Dolby Pro Logic
Dolby Digital 5.1-channel audio is a discrete multi-channel surround sound format that is increasingly popular today to provide a realistic theater experience in your home. Discrete means that the audio information contained in the six individual channels is specific to that one channel and independent from any other. There are six channels in a Dolby Digital 5.1 channel setup. Five of the six channels work on a full bandwidth with approximately 3-20kHz for the two front speakers, the center channel, and the two surround speakers. However, there is one LFE or Low Frequency Effects channel for the subwoofer output that is dedicated to a frequency range of 3-120Hz. Because the LFE channel needs only a tenth of the bandwidth of the others channels, the LFE channel is referred to as a .1 channel. This is how the "5.1" for Dolby Digital has been developed.

The five full bandwidth channels provide discrete sound that can be depicted much more accurately for improved dialogue clarity, spaciousness, and realism. The dedicated subwoofer channel of Dolby Digital for the lower frequencies provide much deeper bass than what is offered with Dolby Pro Logic.

Today there are even Dolby Digital 6.1 and 7.1 formats adding one and two rear center channels respectively.

Your receiver will detect the difference in the two tracks and send the two separate sets of information to your left and right front speakers. The stage represents the first two channels of the four-channel track. The information that is identical in each of the first two channels is sent to the center channel. Your center channel represents the third of the four channels. All identical information that is out of phase from the first 3 channels is sent to your rear surround speakers. Your surround speakers represent one channel which make the fourth and last channel for Dolby Pro Logic.