5.1 (pronounced “five point one”), more precisely surround sound 5.1 , describes multi-channel sound systems in which five main channels and a separate low-frequency effect channel are available.
The development of today's widespread 5.1 system comes from cinema technology.
One of the major development steps was done in 1938-1941 by Disney Studios for the film Fantasia . Disney's engineers tried eight different multi-channel formats, the first of which was very similar to today's five-channel system (three channels in front, two in back).
In the course of this development, Disney engineers invented multi-channel recording, pan potting (moving a signal between channels) and overdubbing (adding additional recordings to a recording). This technique became known as "Fantasound". Since this multi-channel film remained the only one for a long time, practically no cinemas were converted and the technology was forgotten.
Was developed as the technology of magnetic sound recording was not until the 1950s, produced 20th Century Fox in association with Cinemascope (three front channels and a four-channel movies mono - surround channel), while the sound on tape was delivered to the film. A time followed in which stereo prevailed both in performance and in sound carriers, Dolby Stereo was developed (improvement of dynamics).
Only with the movie Star Wars did the development get moving again, the producer Gary Kurtz and Dolby Personal developed an additional bass channel ("Baby Boom" channel) for the 70 mm copies in order to increase the representation of the bass dynamics (today with the 0.1 channel to compare). The surround channel was still in mono . The first “real” dedicated subwoofer was used in the film Close Encounters , two years later the surround array was split into two channels for the film Superman , Apocalypse Now also used this setup.
From this point onwards, a setup comparable to today's 5.1 system was used for some 70 mm films.
In 1987 a subcommittee of the "Society of Motion Picture and Television Engineers" met and defined the 5.1 system as the minimum number of channels for a sufficient sound experience in connection with the digitization of the sound, which practically became the current 70 mm practice approved.
Components of the 5.1 system are:
- Main speaker left, center and right (LCR)
- Surround speakers left and right rear (LsRs)
- Woofer (LFE, "Low Frequency Effects" or "Low Frequency Enhancement")
The format was originally only used in the cinema, in the early 1990s 5.1 was standardized for digital television, since the introduction of DVD as a video storage medium it has also been used in the home, albeit with slightly different requirements (see below).
With 5.1, all six channels are stored and played back discretely - that is, not matrixed as with Dolby Surround .
The five channels for front, center and surround can store and reproduce all audible frequencies (20–20,000 Hz).
The LFE channel only reproduces low frequencies between 20 and 120 Hz. “.1” means an LFE channel that only reproduces frequencies with 1/200 of the general sampling rate (“.1” should actually be called .005, but has been simplified to “.1”). “.1” does not mean that there is only one LFE channel, so there is no 5.2.
A distinction must be made between 5.1 systems for cinema and home applications.
Use in the cinema
The goal when using it in the cinema is a high level of speech intelligibility and centralized localization of the main actors on all seats. This has to be achieved through the center loudspeaker behind the screen, since in the cinema the stereo triangle can only be guaranteed for a very small proportion of the audience. A viewer seated far to the left would therefore practically only hear the main actors from the left in pure stereo playback in the cinema, while he would see them in the picture a few meters further to the right, which would be very irritating.
A high volume level for effects can be generated by separately controlling the subwoofer and an “enveloping sound” can be generated by the surround speakers. The latter is achieved by using a large number of loudspeakers and / or diffuse radiating loudspeakers ( dipoles , bipoles) to the side and behind the audience. Because of this diffusity, clearly definable sound events are seldom placed in the surround speakers.
The goal is a good localization of all sound sources and the uniformity of all sound events reproduced in the room for a centrally seated listener. Ideally, five identical full-range loudspeakers are used for the front, center and surround; the subwoofer and center are less important than in cinemas. Music recordings in particular are often mixed without a center and LFE channel. The requirement of a strictly centralized localization as with a large audience in a cinema does not exist at home.
The installation standard according to ITU -R BS was developed for home playback in 5.1 . This provides:
- five identical speakers for front, center and surround
- identical distance of all five loudspeakers to the listener
- Angular arrangement of the loudspeakers in the listener's line of sight: center 0 °, front ± 30 °, surround ± 100–120 °; so rather to the side, not behind the receiver.
The installation of full-fledged and largely free-standing hi-fi speakers in such a configuration in a living room, however, requires a certain minimum size and a suitable floor plan. This fact stands in the way of a wider spread of the 5.1 multi-channel sound system for high-quality music reproduction.
The side localization of sound hardly works either. It is compatible with a 5.1 system e.g. B. not possible to clearly depict a sound event coming from the right (i.e. 90 ° from the viewing direction).
Since the designations "X.1" (X = 4, 5, 6, 7, ...) are not standardized, many devices in the home sector are provided with labels that artificially generate loudspeaker channels from the existing sound for reasons of better marketability. So z. For example, the designation “6.1” suggest a better sound experience than “5.1”, even if the additional “channel” is only generated from the summation of two other channels.
The SDDS format, which is only used in the cinema, has a 7.1 arrangement in which an additional loudspeaker is inserted between the left and right front loudspeakers, which enables the construction of even wider cinema halls with improved localization.
In addition, 7.1 sound formats for film playback (especially on Blu-ray Disc and HD DVD ) have recently been offered, with a half-rear loudspeaker in the middle between the front and rear loudspeakers on each side for an even smoother sound transition should allow from back to front and vice versa.
- Rolf Seidelmann: Surround in the music studio . Wizoobooks, Bremen 2008, ISBN 978-3-934903-69-2 .
- Holman Tomlinson: 5.1 Surround Sound - Up an Running . Focal Press, Boston Oxford Auckland Johannesburg Melbourne New Delhi 2000, ISBN 0-240-80383-3 .