Surround Sound

Surround sound encompases a range of techniques for enriching the sound reproduction quality of an audio source with audio channels reproduced via additional, discrete speakers. The three-dimensional (3D) sphere of human hearing can be virtually achieved with audio channels above and below the listener. To that end, the multichannel surround sound application encircles the audience (left-surround, right-surround, back-surround), as opposed to “screen channels” (center, [front] left, and [front] right), i.e. ca. 360° horizontal plane, 2D).

Surround sound technology is used in cinema and home theater systems, video game consoles, personal computers and other platforms. Commercial surround sound media include videocassettes, Video DVDs, and HDTV broadcasts encoded as Dolby Pro Logic, Dolby Digital, or DTS. Other commercial formats include the competing DVD-Audio (DVD-A) and Super Audio CD (SACD) formats, and MP3 Surround. Cinema 5.1 surround formats include Dolby Digital, DTS, and Sony Dynamic Digital Sound (SDDS).

Most surround sound recordings are created by film production companies or video game producers; however some consumer camcorders have such capability either built-in or available separately. Surround sound technologies can also be used in music to enable new methods of artistic expression. After the failure of quadraphonic audio in the 1970s, multichannel music has slowly been reintroduced since 1999 with the help of SACD & DVD-Audio formats. Some AV receivers, stereophonic systems, and computer soundcards contain integral digital signal processors and/or digital audio processors to simulate surround sound from a stereophonic source.

The descriptions of surround sound specifications below distinguish between the number of discrete channels encoded in the original signal and the number of channels reproduced for playback. The number of channels reproduced for playback can be changed by using matrix decoding. A distinction is also made between the number of channels reproduced for playback and the number of speakers used to reproduce (each channel may refer to a group of speakers). The graphics to the right of each specification description represent the number of channels, not the number of speakers.

Notation

This notation, e.g. “5.1″, reflects the number of full range channels; including a “.1″ to reflect the limited range of the LFE channel.

E.g. 2 basic stereo speakers with no LFE channel = 2.0
5 full-range channels + 1 LFE channel = 5.1

It can also be expressed as the number of full-range channels in front of the listener, separated by a slash from the number of full-range channels beside or behind the listener, separated by a decimal point from the number of limited-range LFE channels.

E.g. 3 front channels + 2 side channels + an LFE channel = 3/2.1

This notation can then be expanded to include the notation of Matrix Decoders. Dolby Digital EX, for example, has a sixth full-range channel incorporated into the two rear channels with a matrix. This would be expressed:

3 front channels + 2 rear channels + 3 channels reproduced in the rear in total + 1 LFE channel = 3/2:3.1

Note: The term stereo, although popularised in reference to two channel audio, can also be properly used to refer to surround sound, as it strictly means “solid” sound. However this is no longer a common usage and “stereo sound” is almost exclusively used to describe two channel left and right sound.

3.0 Channel Surround (Dolby 3 Stereo)

• Two channels for speakers at the front-left (L) and right (R).
• One channel for a center speaker.

This format is used for a wide stereo image without a “gap” in the middle. It is often included with systems with Pro Logic (1) decoders, and was introduced in cinemas in 1975. This format was sometimes included in television sets where, when activated, two external speakers were connected and the TV speaker acted as the center channel. This is also known as Dolby Stereo.

3.0 Channel Surround (analog matrixed: Dolby Surround)

Extracts 3 audio channels from a specially encoded two-channel source:

• Two channels for speakers at the front—left (L) and right (R).
• One channel for surround speaker or speakers at the rear—surround (S).
• Describes the numerous matrixed (pre- Pro Logic) surround processors.

Placement: (three speakers in total) Three identical speakers placed equidistant around a central listening position. If two rear speakers are used they should also be placed above ear height, slightly behind the listening position, and should be of bi-polar construction.

4.0 Channel Surround (analog matrixed/discrete: Quadraphonic)

Extracts four audio channels from either a specially encoded two-channel source or a four-channel source:

• Two channels for speakers at the front—left (L) and right (R).
• Two channels for surround speakers at the rear—surround left (LS) and surround right (RS). Some newer receivers support the LFE channel.
• Describes the early matrixed systems and discrete Quadraphonic surround systems. Source media, usually LP record or tape, is often branded four channel stereo.

Placement: Quadraphonics is a system designed for music only. All speakers should be at an ±45˚. All speakers should be above ear height.

4.0 or 4.1 Channel Surround (analog matrixed: Dolby Pro Logic)

Extracts four audio channels from a specially encoded two-channel source:

• Two channels for speakers at the front—left (L) and right (R).
• One channel for speaker at the center—center (C).
• One channel for both surround speakers at the rear—mono surround channel (S).
• One low-frequency effects channel (LFE) for a subwoofer (optional).
• Describes the Dolby Pro Logic matrixed surround system. Source media, usually VHS, Laser Disc, television broadcast or CableTV/Satellite is often branded with “Dolby Surround” logo. This is the encoding used on the analog optical track for theatrical motion picture films.

Placement: (Five speakers in total) The front speakers should be placed at the edges of the screen, toed in to face the central listening location, and the tweeters should be ear height. The center speaker should be placed behind the screen (when using projection) or over or under a TV, and as close to ear-high as possible. Surround channel speakers should be placed above ear height, slightly behind the listening position, and should be of bi-pole construction. LFE subwoofer may be placed anywhere within the room.

5.1 Channel Surround (3-2 Stereo) (analog matrixed: Dolby Pro Logic II)

Extracts Five audio channels from either a specially encoded two-channel or a stereo source:

• Two channels for speakers at the front—left (L) and right (R).
• One channel for speaker at the center—center (C).
• Two channels for surround speakers at the rear—surround left (LS) and surround right (RS).
• One low-frequency effects channel (LFE).
• Describes the Dolby Pro Logic II matrixed surround system. Source media is often gaming systems including Playstation 2, GameCube and Wii games branded with “Pro Logic II” logo.

5.1 surround sound may also be referred to as 3-2 stereo. This defines the configuration that has been standardised for numerous surround sound applications. The term 3-2 refers to 3 front speakers and 2 rear speakers.

Placement: 5.1 speaker layouts should conform to the ITU-R BS.775 standard, despite the myth that music and video content require different placements. The ITU standard states that the left and right speakers are located at ±30˚, while the rear speakers should be positioned approximately ±110˚. There is speculation that rear loudspeakers at ±150˚ provide “more exciting surround effects”.

5.1 Channel Surround (70 mm 6-Track) (analog magnetic)

Delivers six audio channels from a 6 channel source:

• Four channels for speakers at the front-left (L), left center (LC), right center (RC), and right (R).
• One channel for speaker at the center-center (C)
• One channel for surround speaker at the rear-monaural surround (S)

5.1 Channel Surround (3-2 Stereo) (analog magnetic: Dolby Stereo “Baby Boom”)

Delivers five audio channels and 1 LFE channel from a 6 channel source:

• Two channels for speakers at the front—left (L) and right (R).
• One channel for speaker at the center—center (C).
• Two channels for surround speakers at the rear—surround left (LS) and surround right (RS).
• One low-frequency effects channel (LFE).

5.1 Channel Surround (3-2 Stereo) (digital discrete: Dolby Digital, DTS, SDDS, Penteo)

Delivers Five discrete audio channels and 1 LFE channel from a 6 channel source:

• Two channels for speakers at the front—left (L) and right (R).
• One channel for speaker at the center—center (C).
• Two channels for surround speakers at the rear—surround left (LS) and surround right (RS).
• One low-frequency effects channel (LFE).
• Describes the Dolby Digital, Digital Theater System (DTS), and Sony Dynamic Digital Sound (SDDS) systems. Source media, usually DVD and sometimes Laser Disc or satellite/digital cable is often branded with “Dolby Digital” and/or DTS logos.
• Although DTS uses a higher data rate than Dolby Digital, this doesn’t mean that the fidelity is higher.

5.1 surround sound may also be referred to as 3-2 stereo. This defines the configuration that has been standardised for numerous surround sound applications. The term 3-2 refers to 3 front speakers and 2 rear speakers.

Placement: 5.1 speaker layouts should conform to the ITU-R BS.775 standard, despite the myth that music and video content require different placements. The ITU standard states that the left and right speakers are located at ±30˚, while the rear speakers should be positioned approximately ±110˚. There is speculation that rear loudspeakers at ±150˚ provide “more exciting surround effects”.

6.1 Channel Surround (analog matrixed: Dolby Pro Logic IIx)

Extracts six audio channels and one low-frequency channel from either a specially encoded two-channel or stereo source. Expands a back surround channel from a 5.1 channel source:

• Two channels for speakers at the front—left (L) and right (R).
• One channel for speaker at the center—center (C).
• Two channels for surround speakers at the sides—side left (LS) and side right (RS).
• One channel for surround speakers at the rear—back surround channel (BS).
• One low-frequency channel to drive a sub-woofer.
• Describes the Dolby Pro Logic IIx matrixed surround system. Source media is the same as both Dolby Pro Logic and Dolby Pro Logic II.

Placement: The front speakers should be placed at the edges of the screen, toed in to face the central listening location. The center speaker should be placed behind the screen (when using projection) or over or under a TV. Side channel speakers should be placed to the left and right of the listening position, equidistant from the front speakers and the rear speakers. Rear channel speakers should be placed slightly behind the listening position, and should have a normal high-quality monopolar construction. Front speakers should be at ear height and surrounds should be above.

6.1-7.1 Channel Surround (digital partially discrete: Dolby Digital EX)

Delivers five audio channels, one extracted audio channel and one LFE channel from a six channel source:

• Two discrete channels for speakers at the front—left (L) and right (R).
• One discrete channel for speaker at the center—center (C).
• Two channels for surround speakers at the sides—left surround (LS) and right surround (RS). The discrete LS and RS channels are dematrixed into LS, RS, and back surround (BS).
• One channel for surround speakers at the rear—back surround channel (BS). The back surround channel can be made into two channels by the receiver.
• One low-frequency effects channel (LFE).
• Describes the Dolby Digital EX discrete/matrixed hybrid Surround system. Source media, usually DVD is often branded with “Dolby Digital EX” logo. This format is used in some theatrical motion picture films.

Placement: The front speakers should be placed at the edges of the screen, toed in to face the central listening location. The center speaker should be placed behind the screen (when using projection) or over or under a TV. Side channel speakers should be placed to the left and right of the listening position, equidistant from the front speakers and the rear speakers. Rear channel speakers should be placed slightly behind the listening position, and should have a normal high-quality monopolar construction. Front speakers should be at ear height and surrounds should be above ear height.

6.1 Channel Surround (digital discrete: DTS-ES)

Delivers six discrete audio channels and 1 LFE channel from a seven channel source:

• Two channels for speakers at the front—left (L) and right (R).
• One channel for speaker at the center—center (C).
• Two channels for surround speakers at the sides—side left (LS) and side right (RS).
• One channel for surround speakers at the rear—back surround channel (BS).
• One low-frequency effects channel (LFE).
• Describes the DTS ES discrete Surround system. Source media, usually DVD is often branded with “DTS ES” logo. In theatrical motion picture film, this format does not exist, and the name “DTS-ES” refers to the above hybrid format used for Dolby Digital EX.

Placement: The front speakers should be placed at the edges of the screen, toed in to face the central listening location. The center speaker should be placed behind the screen (when using projection) or over or under a TV. Side channel speakers should be placed to the left and right of the listening position, equidistant from the front speakers and the rear speakers. Rear channel speakers should be placed slightly behind the listening position, and should have a normal high-quality monopolar construction. For films, it is generally recommended that front speakers should be at ear height and surrounds should be above ear height, whereas for multichannel music, all main speakers should be at ear height.

Assuming the 60° speaker separation common with stereo, six speakers should then be sufficient to envelop the listener in the horizontal plane.

6.1 Channel Surround (analog magnetic) Cinerama 7-Track

Delivers seven audio channels from a 7 channel source:

• Four channels for speakers at the front-left (L), left-center (LC), right-center (RC), and right (R).
• One channel for the center (C)
• Two channel switchable surround that could feed one channel on the left and right walls and the other in the rear or could feed one channel on the left and one on the right.

Placement: The first five speakers should be placed across the wall on top of the screen or behind the screen. There should be three surround channels on the left, right, and rear walls. Switchable surround sound was done manually by a theater engineer based upon cue marks.

7.1 Channel Surround (digital discrete: Dolby Digital Plus, DTS-HD Master Audio, Dolby TrueHD, SDDS)

See also: 8 channel audio

Delivers seven audio channels and one LFE channel from an 8 channel source:

• Two channels for speakers at the front—left (L) and right (R).
• One channel for speaker at the center—center (C).
• Two channels for surround speakers at the sides—left surround (LS) and right surround (RS).
• Two channels for surround speakers at the rear—left back (LB) and right back (RB).
• One low-frequency effects channel (LFE).
• Describes the Dolby Digital Plus discrete Surround system. Source media, usually Blu-Ray and sometimes HD-DVD are often branded with “Dolby Digital Plus”, “DTS-HD Master Audio” and/or “Dolby TrueHD” logos.

Layout variation for 7.1 widescreen cinema format:

• Four channels for speakers at the front—left (L), center-left (CL), center-right (CR) and right (R).
• One channel for speaker at the center—center (C).
• Two channels for surround speakers at the rear—surround left (LS) and surround right (RS).
• One low-frequency effects channel (LFE).

8-channel SDDS uses this layout variation.

This variation is becoming increasingly popular in home entertainment systems, as well as for large cinema auditoria where the screen width is such that the additional channels are needed to cover all angles between the loudspeakers satisfactorily for all seats in the auditorium.

For music, speaker placement is unknown.

Placement: The front speakers should be placed at the edges of the screen, toed in to face the central listening location, and the tweeters should be ear height. The center speaker should be placed behind the screen (when using projection) or over or under a TV, and as close to ear height as possible. Side channel speakers should be placed on side walls, to the left and right of the listening position, equidistant from the front speakers and the rear speakers. Rear channel speakers should be placed on side walls, slightly behind the listening position, and should have a normal high-quality monopolar construction. Front speakers should be at ear height and surrounds should be above ear height.

Channel identification

In accordance with ANSI/CEA-863-A

Sonic Whole Overhead Sound

In 2002, Dolby premiered a master of We Were Soldiers which featured a Sonic Whole Overhead Sound soundtrack. This mix included a new ceiling-mounted height channel.

10.2 Channel Surround

10.2 is the surround sound format developed by THX creator Tomlinson Holman of TMH Labs and University of Southern California (schools of Cinema/Television and Engineering). Developed along with Chris Kyriakakis of the USC Viterbi School of Engineering, 10.2 refers to the format’s promotional slogan: “Twice as good as 5.1″. Advocates of 10.2 argue that it is the audio equivalent of IMAX.

10.2 augments the LS (left surround) and RS (right surround) channels by two point surround channels that can more finely manipulate sound—allowing the mixer to shift sounds in a distinct 360° circle around the movie watcher.

The 14 discrete channels are:

• Five front speakers: Left Wide, Left, Center, Right and Right Wide
• Five surround channels: Left Surround Diffuse, Left Surround Direct, Back Surround, Right Surround Diffuse and Right Surround Direct
• Two LFE channels: LFE Left, LFE Right
• Two Height channels: Left Height, Right Height

The .2 of the 10.2 refers to the addition of a second subwoofer. The system is bass managed such that all the speakers on the left side use the left sub and all the speakers on the right use the right sub. The Center and Back Surround speaker are split among the two subs. The two subs also serve as two discrete LFE (Low Frequency Effects) channels. Although low frequencies are not localizable, it was found that splitting the bass on either side of the audience increases the sense of envelopment.

22.2 Channel Surround

22.2 is the surround sound component of Ultra High Definition Video (Super Hi-vision TV with 4320 scanning lines), and has been developed by NHK Science & Technical Research Laboratories. As its name suggests, it uses 24 speakers. These are arranged in three layers: A middle layer of ten speakers, an upper layer of nine speakers, and a lower layer of three speakers and two sub-woofers. The system was demonstrated at Expo 2005, Aichi, Japan, the NAB Shows 2006 & 2009, Las Vegas, and the IBC trade shows 2006 & 2008, Amsterdam, Netherlands.

Ambisonics

Ambisonics is a series of recording and replay techniques using multichannel mixing technology that can be used live or in the studio. Any number of speakers in any physical arrangement can be used to recreate a sound field. With 6 or more speakers arranged around a listener, a 3-dimensional (“periphonic”, or full-sphere) sound field can be presented. Ambisonics was invented by Michael Gerzon and others.

Panor-Ambiophonic (PanAmbio) 4.0/4.1

PanAmbio combines a stereo dipole and crosstalk cancellation in front and a second set in back of the listener (total of four speakers) for 360° 2D surround reproduction. Four channel recordings, especially those containing binaural cues, create speaker-binaural surround sound. 5.1 channel recordings, including movie DVDs, are compatible by mixing C-channel content to the front speaker pair. 6.1 can be played by mixing SC to the back pair.

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