5.1 Channel

5.1 声道 consists of three front channels (left, center, and right), two side-rear channels (left surround and right surround), and a low-frequency effects channel. The reference layout specified in ITU-R BS.775 places the left and right front channels approximately 30° on either side of the central axis, with the surround channels located in the 100° to 120° region; different cinema and home theater standards may provide further specifications regarding naming, angles, and installation heights.

The center channel typically carries dialogue or main subjects related to the center of the screen, while the left and right channels establish the front soundstage, and the surround channels provide sound from the side and rear directions as well as ambient sound. The LFE is typically limited to frequencies below approximately 120 Hz and is used for additional low-frequency effects. The LFE does not represent the sum of all bass frequencies; the five main channels can still carry low frequencies across the full bandwidth.

A single LFE channel does not mean that only one subwoofer can be connected. Bass management can route content from the main speakers below the crossover point, along with the LFE, to one or more subwoofers; conversely, when no subwoofer is present, the system may redirect the LFE and low frequencies to the main speakers capable of handling them.

Formats such as Dolby Digital, DTS, LPCM, Dolby TrueHD, and DTS-HD Master Audio can all support 5.1, but encoding methods and channel layouts are distinct characteristics. The decoded output of Cinema 5.1, Music 5.1, and historical matrix surround may use the same number of channels but have different production objectives and frequency band allocations.