Surround channels
Encyclopedia
Surround channels are audio channels in surround sound
multichannel audio. They primarily serve to deliver ambience
and diffuse sounds in a film or music soundtrack. Unlike most typical speaker placements, surround speakers are often intended to radiate such that the sound reflects off walls so that the sound arrives at the listening position indirectly as a reflection rather than a direct wave. Often dipole (sometimes even quadrupole
) speakers are used to do this, especially in small or home theater
applications where an array of surround speakers as in a movie theater is not practical or possible. A common misconception is that surround channels are "rear channels." However, when only two speakers are used, they are meant to be placed on the side walls at 90-110 degrees relative to the screen. Surround speakers are placed above the listeners ears and are not angled towards the listener. In cinema
setups, many more than two surround speakers are often used, being placed along the side walls and along the back wall, creating a very diffused sound in the auditorium.
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For music surround channel information is intended to be more direct as in a soundstage there would be direct noise from all around and not ambience as in a movie setting. For this reason surround speakers should not be set up to be strictly diffuse. Optimally there should be discrete surround channels for diffuse and direct effects. This is part of the design for Tomlinson Holman's 12.2 (10.2) surround sound
. For movies surround channel information is usually more diffuse ambient noise.
Some surround sound systems such as Dolby Digital EX and Pro Logic IIx incorporate a third (back surround) or even fourth surround channel (back left and back right). These channels are matrixed from the standard surround channels; they are not discrete.
from the 1930s used a surround channel). Dolby Surround
(1982) was the first home audio system to use a rear channel. It and its successor, Dolby Pro Logic (1987), used a single rear surround channel, but often using two speakers connected in anti-phase or a dipole radiator, as shown in the speaker configuration diagram to the right in gray.
Some matrix encoding surround sound systems use a single back center channel
surround (Dolby Digital EX, Dolby Pro Logic IIx 6.1) or a back left and back right (Dolby Pro Logic IIx 7.1) speaker configuration. Often the standard surround channels are misconceived to be "rear channels" when they are in fact meant to be placed at 90-120 degrees.
states that surround speakers should be spaced evenly along the side and back walls, starting at no closer than 1/3 of the room length from the screen (so the surrounds do not interfere with the front channels) and should be located at about 10–12 feet high and angled down to face the opposite wall-floor boundary.
Surround sound
Surround sound encompasses a range of techniques such as for enriching the sound reproduction quality of an audio source with audio channels reproduced via additional, discrete speakers. Surround sound is characterized by a listener location or sweet spot where the audio effects work best, and...
multichannel audio. They primarily serve to deliver ambience
Ambience (sound recording)
In filmmaking, ambience consists of the sounds of a given location or space. It is the opposite of "silence." This term is often confused with presence....
and diffuse sounds in a film or music soundtrack. Unlike most typical speaker placements, surround speakers are often intended to radiate such that the sound reflects off walls so that the sound arrives at the listening position indirectly as a reflection rather than a direct wave. Often dipole (sometimes even quadrupole
Quadrupole
A quadrupole or quadrapole is one of a sequence of configurations of—for example—electric charge or current, or gravitational mass that can exist in ideal form, but it is usually just part of a multipole expansion of a more complex structure reflecting various orders of complexity.-Mathematical...
) speakers are used to do this, especially in small or home theater
Home theater
A home theater or home theatre is a theater built in a home, designed to mimic commercial theater performance and feeling, more commonly known as a home cinema...
applications where an array of surround speakers as in a movie theater is not practical or possible. A common misconception is that surround channels are "rear channels." However, when only two speakers are used, they are meant to be placed on the side walls at 90-110 degrees relative to the screen. Surround speakers are placed above the listeners ears and are not angled towards the listener. In cinema
Movie theater
A movie theater, cinema, movie house, picture theater, film theater is a venue, usually a building, for viewing motion pictures ....
setups, many more than two surround speakers are often used, being placed along the side walls and along the back wall, creating a very diffused sound in the auditorium.
10.2
10.2 is the surround sound format developed by THX creator Tomlinson Holman of TMH Labs and University of Southern California . Developed along with Chris Kyriakakis of the USC Viterbi School of Engineering, 10.2 refers to the format's slogan: "Twice as good as 5.1"...
. For movies surround channel information is usually more diffuse ambient noise.
Some surround sound systems such as Dolby Digital EX and Pro Logic IIx incorporate a third (back surround) or even fourth surround channel (back left and back right). These channels are matrixed from the standard surround channels; they are not discrete.
History
Dolby Stereo (1975) was the first standard cinema sound system using a single matrixed mono rear channel (note Disney's FantasoundFantasound
Fantasound was a stereophonic sound reproduction system developed by the engineers of Walt Disney studios for its 1940 animated film Fantasia, the first commercial film to be released in stereo. Fantasound led to the development of what is known today as surround sound.-Origins:Walt Disney's...
from the 1930s used a surround channel). Dolby Surround
Dolby Surround
Dolby Surround was the earliest consumer version of Dolby's multichannel analog film sound decoding format Dolby Stereo introduced to the public in 1982 during the time home video recording formats were introducing Stereo and HiFi capability...
(1982) was the first home audio system to use a rear channel. It and its successor, Dolby Pro Logic (1987), used a single rear surround channel, but often using two speakers connected in anti-phase or a dipole radiator, as shown in the speaker configuration diagram to the right in gray.
Rear/back surround channels
Center channel
Center channel refers to an audio channel common to many surround sound formats. It is the channel that is mostly, or fully, dedicated to the reproduction of the dialogue of an audiovisual program...
surround (Dolby Digital EX, Dolby Pro Logic IIx 6.1) or a back left and back right (Dolby Pro Logic IIx 7.1) speaker configuration. Often the standard surround channels are misconceived to be "rear channels" when they are in fact meant to be placed at 90-120 degrees.
Surround arrays
In commercial cinema, where there is a large area to cover, it would be impractical to use a single speaker for each surround channel. Theater auditoriums are often lined with speakers all along the side and back walls. This is to increase the size of the listening area. JBLJBL
JBL is an American audio electronics company currently owned by Harman International. It was founded in 1946 by James Bullough Lansing. Their primary products are loudspeakers and associated electronics. There are two independent divisions within the company — JBL Consumer and JBL Professional...
states that surround speakers should be spaced evenly along the side and back walls, starting at no closer than 1/3 of the room length from the screen (so the surrounds do not interfere with the front channels) and should be located at about 10–12 feet high and angled down to face the opposite wall-floor boundary.