5.1 surround sound

5.1 (pronounced " five point one"), or more precisely 5.1 surround sound, called multi -channel sound systems, which focus on five main channels and a separate Tieftoneffektkanal available.

Development

The development of today's popular 5.1 system comes from the cinema technology.

One of the major development work was done 1938-41 by the Disney Studios for the movie " 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 front, two rear ). In the course of this development the Disney engineers invented the multi-channel recording, Pan potting (Moving a signal between channels ) and overdubbing ( a complete recording by additional recordings). This technique became known as " Fanta Sound". As this multi-channel movie for a long time remained the only, no cinemas were practically rebuilt and the technology fell into oblivion.

Only in the 1950s, when the technology of magnetic recording has been developed, 20th Century Fox produced in conjunction with CinemaScope Four Channel movies ( three front channels and a mono surround channel), while the sound on the tape was delivered to the film. There was a time when stereo prevailed both in performance and in recordings, it was Dolby Stereo developed (improved dynamics).

Only with the movie "Star Wars" came back movement in the development of producer Gary Kurtz developed with Dolby staff for the 70 - mm prints an additional bass channel ( " baby boom " channel ) to increase the representation of the range bass (now compared with the 0.1- channel). The surround channel was there still running in mono. The first "real" dedicated subwoofer was used in the movie " Close Encounters ", two years later for the film " Superman", the surround array divided into two channels, "Apocalypse Now", also used this setup. From this point, a comparable with the current 5.1 system setup has been used for some 70 - mm films.

In 1987, a Subkommitee the " Society of the Motion Picture and Television Engineers " together and defined in relation to the digitization of the sound the 5.1 system as a minimum of channels for an adequate sound experience, so that the common 70 -mm practice was practically confirmed.

Components of the 5.1 system are:

• Main speakers left, center and right ( LCR)
• Surround left speaker and right rear ( LsRs )
• Woofer (LFE " Low Frequency Effects " or "Low Frequency Enhancement " )

The format was originally used only in the cinema, in the early 1990s was 5.1 standardized for digital TV, since the DVD launch as a video DVD, it is also located in the home, but with slightly different requirements ( see below).

In 5.1, all six channels are discretely - not as matrixed Dolby Surround - stored and reproduced.

The five channels for front, center and surround can save all audible frequencies ( 20-20,000 Hz) and play.

The LFE channel reproduces low frequencies between 20 and 120 Hz. " .1 " Indicates a LFE channel, which reproduces only frequencies with 1/ 200 of the overall sampling rate ( " .1" would actually .005 hot, but was " .1" simplified ). " .1" Therefore does not mean that only one LFE channel is present, so there is no 5.2! In the production of Kinofilmton the LFE channel is basically used only for effects, in which a physically tangible, deep sound with high sound pressure to be generated, for example, for the reinforcement of explosions and shots.

In the home of the LFE channel is sometimes " abused " as a subwoofer to reproduce the information contained in the main channels low frequencies that are fed to it via a crossover. This small and inexpensive main speakers are relieved in particular.

Main Applications

One must distinguish between 5.1 systems for cinema and home applications.

Application in the cinema

The aim in applying the cinema is a high speech intelligibility and central localization of the main characters in all seats. This must be achieved by the center speaker behind the screen, as in the movies, the stereo triangle can be guaranteed only for a small proportion of the audience. A far left seated spectators would therefore practically hear the lead actor in pure stereo playback in the cinema from left, as he would see it in the picture a few meters to the right, which would be very irritating.

A high volume level effects can be achieved by separate control of the subwoofer, and a " sound envelope " will be produced by the surround speakers. The latter is achieved by the use of a variety of speakers and / or diffuse radiating speakers ( dipoles, bipoles ) beside and behind the audience. Because of this vagueness rarely clearly defined sound events are placed in the surround speakers.

Home Use

The goal is a good localization of all sound sources and the uniformity of all reproduced in the room sound events for a centrally seated listener. Therefore Ideally, five identical full-range speakers for front, center and surround are used, the importance of the center and subwoofer is lower than in the cinema environment. Often specially recorded music without center and LFE channel will be mixed. The requirement of a strictly central location such as at a large audience in the cinema is not at home.

For home playback in 5.1, the Accounting standard ITU-R BS was developed. This provides:

• Five identical speakers for front, center and surround
• Identical distance of all five speakers to the listener
• Angular arrangement of the speakers in the viewing direction of the listener: Center 0 °, ± 30 ° front, surround ± 100-120 °; So rather sideways, not behind the listener.

Problems

The preparation of full-fledged and largely free-standing Hi- Fi speakers in such a configuration in a living room of this, however, requires a certain minimum size and a suitable floor plan. This circumstance precludes a wider distribution of the 5.1 multi-channel sound system to high-quality music reproduction.

The side localization of sound works practically no. It is not possible for example with a 5.1 system, ( ie 90 ° seen from the viewing direction wise) clearly depict coming from the right sound event.

Since the terms " X.1 " (X = 4, 5, 6, 7, ... ) are not standardized, many devices are provided with such labels in the home for reasons of better marketability, the artificially generate speaker channels from the existing tone. As is, for example, the designation " 6.1", a better listening experience suggest as " 5.1", even if the additional "channel" is generated only from the summation of two other channels.

Development

A further development, however, with rather low potential for improvement are 6.1 - processes in which an additional rear center is used, for example, Dolby Digital EX.

The format SDDS used only in the movies has a 7.1 - arrangement in which each of the left and right front speakers, an additional speaker is still inserted, allowing the construction of even larger movie theaters with improved localization.

In addition, more recently, 7.1 audio formats for video playback are available (especially on Blu -ray and HD - DVD), in which the center between the front and rear speakers on each side of a half- rear speakers an even smoother note transition from back to front and vice versa to enable.