Dolby Digital provides five full bandwidth channels: front left, front right, center, surround left, and surround right, for true surround sound quality. A low frequency effect (LFE) channel is included that provides the sound needed for special effects and action sequences in movies. The LFE channel is one tenth of the bandwidth of the other channels and is sometimes erroneously called the subwoofer channel. This multichannel scheme is known as 5.1 channel.
Because not everyone has the equipment needed to take advantage of Dolby Digital's 5.1 channel, developers included a downmixing feature that ensures compatibility with any playback device. The decoder in the playback device delivers the audio signal specific to that particular device's ability. For example, a 5.1 channel audio signal is delivered to a mono television. The playback device's decoder downmixes the 5.1 channel signal to a mono signal allowing the television to use the received audio signal. Because the playback device does the downmixing, producers do not have to create multiple audio signals for each playback device.