History
The need for a center speaker to locate screen-centered sounds has been recognised since the Bell labs experiments in stereo sound from the 1930s, and multi-channel cinema sound systems, starting with the first commercial stereophonic film (Fantasia-1941) have always included one. Post-war stereo sound in theaters initially came from separate magnetic film reproducers synchronised to the picture, but in the 1950s systems using magnetic stripes on the film itself came into use. Cinemascope used four such tracks (left, center, right and surround), and the subsequent Todd-AO 70mm system used six (left, left-center, center, right-center and right, plus a single surround channel). Unfortunately these magnetic systems were not only very expensive, but were also unreliable and so were little used, the industry preferring to stay with the tried, tested (and cheap) mono optical track.
Dolby Stereo was introduced by Dolby Laboratories in 1975. It divided the existing soundtrack area of a 35mm film print into two, allowing a two-channel recording. Each of these two channels used Dolby A type noise reduction (later replaced by Dolby SR type). In addition a matrix, similar in principle to those used for the existing matrix-type quadraphonic systems, allowed the audio for left, center and right speakers, plus a single surround channel to be carried by the two tracks. Thus Dolby Stereo provided a similar stereo performance to that previously only available in the cinema by the magnetic tracks on 4-track Cinemascope or 6-track Todd-AO (70mm) formats, but at far lower cost.
Dolby Pro Logic is the name used for the Dolby Stereo matrix when used in home theater systems.
In recent years digital multi-channel sound systems, such as Dolby Digital and DTS, have become available which provide 6 or 8 discrete audio channels providing for not only the usual three screen speakers but also 2 or 4 groups of surround speakers and a sub-woofer.
Read more about this topic: Center Channel
Famous quotes containing the word history:
“Most events recorded in history are more remarkable than important, like eclipses of the sun and moon, by which all are attracted, but whose effects no one takes the trouble to calculate.”
—Henry David Thoreau (1817–1862)
“In every election in American history both parties have their clichés. The party that has the clichés that ring true wins.”
—Newt Gingrich (b. 1943)
“No one can understand Paris and its history who does not understand that its fierceness is the balance and justification of its frivolity. It is called a city of pleasure; but it may also very specially be called a city of pain. The crown of roses is also a crown of thorns. Its people are too prone to hurt others, but quite ready also to hurt themselves. They are martyrs for religion, they are martyrs for irreligion; they are even martyrs for immorality.”
—Gilbert Keith Chesterton (1874–1936)