prototype at the Opera during the World Exhibition in Paris (1881)
Early work by
Berthold Laufer for
Franz Boaz in 1901
Clément Ader demonstrated the first two-channel audio system in Paris in 1881, with a series of telephone transmitters connected from the stage of the
Paris Opera to a suite of rooms at the Paris Electrical Exhibition, where listeners could hear a live transmission of performances through receivers for each ear.
Scientific American reported: This two-channel telephonic process was commercialized in France from 1890 to 1932 as the
Théâtrophone and in England from 1895 to 1925 as the
Electrophone. Both were services available by coin-operated receivers at hotels and cafés or by subscription to private homes. There have been cases in which two recording lathes (for the sake of producing two simultaneous masters) were fed from two separate microphones; when both masters survive, modern engineers have been able to synchronize them to produce stereo recordings from a time before intentional stereophonic recording technology existed. In 1925, engineer Heinrich Kluth-Nauen developed a device that created a spatial impression from a mono signal by means of a 180° phase difference. He called it the "Stereophone".
Modern stereophonic sound Modern stereophonic technology was invented in the 1930s by British engineer
Alan Blumlein at
EMI, who patented stereo records, stereo films, and also surround sound. In early 1931, Blumlein and his wife were at a local cinema. The sound reproduction systems of the early
talkies invariably only had a single set of speakers which could lead to the somewhat disconcerting effect of the actor being on one side of the screen whilst his voice appeared to come from the other. Blumlein declared to his wife that he had found a way to make the sound follow the actor across the screen. The genesis of these ideas is uncertain, but he explained them to
Isaac Shoenberg in the late summer of 1931. His earliest notes on the subject are dated September 25, 1931, and his patent had the title "Improvements in and relating to Sound-transmission, Sound-recording and Sound-reproducing Systems". The application was dated December 14, 1931, and was accepted on June 14, 1933, as
UK patent number 394,325. The patent covered many ideas in stereo, some of which are used today and some not. Some 70 claims include: • A
shuffling circuit, which aimed to preserve the directional effect when sound from a spaced pair of microphones was reproduced via stereo headphones instead of a pair of loudspeakers; • The use of a coincident pair of velocity microphones with their axes at right angles to each other, which is still known as a
Blumlein pair; • Recording two channels in the single groove of a record using the two groove walls at right angles to each other and 45 degrees to the vertical; • A stereo disc-cutting head; • Using hybrid transformers to matrix between left and right signals and sum and difference signals; Blumlein began binaural experiments as early as 1933, and the first stereo discs were cut later the same year, twenty-five years before that method became the standard for stereo phonograph discs. These discs used the two walls of the groove at right angles in order to carry the two channels. In 1934, Blumlein recorded
Mozart's
Jupiter Symphony conducted by Sir
Thomas Beecham at
Abbey Road Studios in London using his vertical-lateral technique. In the United States,
Harvey Fletcher of
Bell Laboratories was also investigating techniques for stereophonic recording and reproduction. One of the techniques investigated was the
wall of sound, which used an enormous array of microphones hung in a line across the front of an orchestra. Up to 80 microphones were used, and each fed a corresponding loudspeaker, placed in an identical position, in a separate listening room. Several stereophonic test recordings, using two microphones connected to two styli cutting two separate grooves on the same wax disc, were made with
Leopold Stokowski and the
Philadelphia Orchestra at Philadelphia's
Academy of Music in March 1932. The first (made on March 12, 1932), of
Scriabin's Prometheus: Poem of Fire, is the earliest known surviving intentional stereo recording. The performance was part of an all-Russian program including
Mussorgsky's
Pictures at an Exhibition in the
Ravel orchestration, excerpts of which were also recorded in stereo. Bell Laboratories gave a demonstration of three-channel stereophonic sound on April 27, 1933, with a live transmission of the
Philadelphia Orchestra from Philadelphia to
Constitution Hall in Washington, D.C. over multiple Class A telephone lines. Leopold Stokowski, normally the orchestra's conductor, was present in Constitution Hall to control the sound mix. Five years later, the same system would be expanded onto multichannel film recording and used from the concert hall in Philadelphia to the recording labs at Bell Labs in New Jersey in order to record
Walt Disney's
Fantasia (1940) in what Disney called
Fantasound. Later that same year, Bell Labs also demonstrated binaural sound at the
Chicago World's Fair in 1933 using a
dummy with microphones instead of ears. The two
signals were sent out over separate
AM station bands.
Carnegie Hall demonstration Utilizing selections recorded by the
Philadelphia Orchestra, under the direction of
Leopold Stokowski, intended for but not used in Walt Disney's
Fantasia, the
Carnegie Hall demonstration by
Bell Laboratories on April 9 and 10, 1940, used three huge speaker systems. Synchronization was achieved by making the recordings in the form of three motion picture soundtracks recorded on a single piece of film with a fourth track being used to regulate volume expansion. This was necessary due to the limitations of dynamic range on optical motion picture film of the period; however, the volume compression and expansion were not fully automatic, but were designed to allow manual studio
enhancement; i.e., the artistic adjustment of overall volume and the relative volume of each track in relation to the others. Stokowski, who was always interested in sound reproduction technology, personally participated in the enhancement of the sound at the demonstration. The speakers produced sound levels of up to 100 decibels, and the demonstration held the audience "spellbound, and at times not a little terrified", according to one report.
Sergei Rachmaninoff, who was present at the demonstration, commented that it was "marvellous" but "somehow unmusical because of the loudness." "Take that
Pictures at an Exhibition", he said. "I didn't know what it was until they got well into the piece. Too much 'enhancing', too much Stokowski."
Motion picture era In 1937,
Bell Laboratories in New York City gave a demonstration of two-channel stereophonic motion pictures, developed by Bell Labs and Electrical Research Products, Inc. Once again, conductor
Leopold Stokowski was on hand to try out the new technology, recording onto a special proprietary nine-track sound system at the
Academy of Music in Philadelphia, during the making of the movie
One Hundred Men and a Girl for
Universal Pictures in 1937, after which the tracks were mixed down to one for the final soundtrack. A year later,
MGM started using three tracks instead of one to record the musical selections of movie soundtracks, and very quickly upgraded to four. One track was used for dialogue, two for music, and one for sound effects. The very first two-track recording MGM made (although released in mono) was "It Never Rains But What It Pours" by
Judy Garland, recorded on June 21, 1938, for the movie
Love Finds Andy Hardy. In the early 1940s, composer-conductor
Alfred Newman directed the construction of a sound stage equipped for multichannel recording for 20th Century Fox studios. Several soundtracks from this era still exist in their multichannel elements, some of which have been released on DVD, including
How Green Was My Valley,
Anna and the King of Siam,
The Day the Earth Stood Still and
Sun Valley Serenade which, along with
Orchestra Wives, feature the only stereophonic recordings of the
Glenn Miller Orchestra as it was during its heyday of the
Swing Era.
Fantasound Walt Disney began experimenting with multichannel sound in the early 1930s as noted above. The first commercial motion picture to be exhibited with stereophonic sound was Walt Disney's
Fantasia, released in November 1940, for which a specialized sound process (
Fantasound) was developed. As in the Carnegie Hall demonstrations six months earlier, Fantasound used a separate film containing four optical soundtracks. Three of the tracks were used to carry left, center and right audio, while the fourth track carried three tones which individually controlled the volume level of the other three. The film was not initially a financial success, however, after two months of road-show exhibition in selected cities, its soundtrack was remixed into mono sound for general release. It was not until its 1956 re-release that stereo sound was restored to the film.
Cinerama A
Cinerama demonstration film by
Lowell Thomas and
Mike Todd titled
This is Cinerama was released on September 30, 1952. The format was a widescreen process featuring three separate 35 mm motion picture films plus a separate sound film running in synchronization with one another at 26 fps, adding one picture panel each to the viewer's left and right at 45-degree angles, in addition to the usual front and center panel. The Cinerama audio soundtrack technology, developed by
Hazard E. Reeves, utilized seven discrete sound tracks on full-coat magnetic 35 mm film. The system featured five main channels behind the screen, two surround channels in the rear of the theater, plus a sync track to interlock the four machines, which were specially outfitted with aircraft servo-motors made by
Ampex. The advent of multitrack magnetic tape and film recording of this nature made high-fidelity synchronized multichannel recording more technically straightforward, though costly. By the early 1950s, all of the major studios were recording on 35 mm
magnetic film for mixing purposes, and many of these so-called individual angles still survive, allowing for soundtracks to be remixed into stereo or even surround. In April 1953, while
This is Cinerama was still playing only in New York City, most moviegoing audiences heard stereophonic sound for the first time with
House of Wax, an early
3-D film starring
Vincent Price and produced by Warner Bros. Unlike the
4-track mag release-print stereo films of the period which featured four thin strips of magnetic material running down the length of the film, inside and outside the sprocket holes, the sound system developed for
House of Wax, dubbed WarnerPhonic, was a combination of a 35 mm fully coated magnetic film that contained the audio tracks for left, center and right speakers, interlocked with the two dual-strip
Polaroid system projectors, one of which carried a mono optical surround track and one that carried a mono backup track use in the event anything should go wrong. Only two other films featured this unique hybrid WarnerPhonic sound: the 3-D production of
The Charge at Feather River, and
Island in the Sky. Unfortunately, as of 2012, the stereo magnetic tracks to both these films are considered lost forever. In addition, a large percentage of 3-D films carried variations on three-track magnetic sound:
It Came from Outer Space;
I, the Jury;
The Stranger Wore a Gun;
Inferno;
Kiss Me, Kate; and many others.
Widescreen Inspired by
Cinerama, the movie industry moved quickly to create simpler and cheaper widescreen systems, the first of which,
Todd-AO, was developed by Broadway promoter Michael Todd with financial backing from Rodgers and Hammerstein, to use a single 70 mm film running at 30 frames per second with 6 magnetic soundtracks, for their
screen presentation of Oklahoma!. Major Hollywood studios immediately rushed to create their own unique formats, such as
MGM's
Camera 65,
Paramount Pictures'
VistaVision and
Twentieth Century-Fox Film Corporation's
CinemaScope, the latter of which used up to four separate magnetic soundtracks. VistaVision took a simplified, low-cost approach to stereophonic sound; its
Perspecta system featured only a monaural track, but through subaudible tones, it could change the direction of the sound to come from the left, right or both directions at once. Because of the standard 35 mm-size film, CinemaScope and its stereophonic sound was capable of being retrofitted into existing theaters.
CinemaScope 55 was created by the same company in order to use a larger form of the system (55 mm instead of 35 mm) to allow for greater image clarity onscreen, and was supposed to have had 6-track stereo instead of four. However, because the film needed a new, specially designed projector, the system proved impractical, and the two films made in the process,
Carousel and
The King and I, were released in 35 mm CinemaScope reduction prints. To compensate, the premiere engagement of
Carousel used a six-track magnetic full-coat in an interlock, and a 1961 re-release of
The King and I, featured the film
printed down to
70 mm with a six-channel soundtrack. Eventually, 50 complete sets of combination 55/35 mm projectors and
penthouse reproducers were completed and delivered by Century and Ampex, respectively, and 55 mm release print sound equipment was delivered by Western Electric. Several samples of 55 mm sound prints can be found in the Sponable Collection at the Film and Television Archives at
Columbia University. The subsequently abandoned 55/35 mm Century projector eventually became the Century JJ 70/35MM projector.
Todd-AO After this disappointing experience with their proprietary CinemaScope 55 mm system, Fox purchased the Todd-AO system and re-engineered it into a more modern 24 fps system with new 65 mm self-blimped production cameras (
Mitchell BFC, "Blimped Fox Camera"), new 65 mm MOS cameras (Mitchell FC, "Fox Camera") and new Super Baltar lenses in a wide variety of focal lengths, first employed on
South Pacific. Essentially, although Todd-AO was also available to others, the format became Fox's premier origination and presentation apparatus, replacing the CinemaScope 55 mm system. Current DVDs of the two CinemaScope feature titles were transferred from the original 55 mm negatives, often including the separate 35 mm films as extras for comparison.
Back to mono Beginning in 1957, films recorded in stereo (except for those shown in Cinerama or Todd-AO) carried an alternate mono track for theaters not ready or willing to re-equip for stereo. From then until about 1975, when
Dolby Stereo was used for the first time in films, most motion pictures even some from which stereophonic soundtrack albums were made, such as
Zeffirelli's
Romeo and Juliet were still released in monaural sound, stereo being reserved almost exclusively for expensive musicals such as
West Side Story,
My Fair Lady and
Camelot, or epics such as
Ben-Hur and
Cleopatra. Stereo was also reserved for
dramas with a strong reliance on sound effects or music, such as
The Graduate. Dolby Stereo The Westrex Stereo Variable-Area system was developed in 1977 for
Star Wars, and was no more expensive to manufacture in stereo than it was for mono. The format employs the same Western Electric/Westrex/Nuoptix RA-1231 recorder, and coupled with
QS quadraphonic matrixing technology licensed to Dolby Labs from Sansui, this system can produce the same left, center, right and surround sound of the original CinemaScope system of 1953 by using a single standard-width optical track. This important development, marketed as
Dolby Stereo, finally brought stereo sound to so-called
flat (non-
anamorphic) widescreen films, most commonly projected at aspect ratios of 1.75:1 or 1.85:1.
70 mm projection Producers often took advantage of the six magnetic soundtracks available for
70 mm film release prints, and productions shot in either 65 mm or to save money, in 35 mm and then blown up to 70 mm. In these instances, the 70 mm prints would be mixed for stereo, while the 35 mm reduction prints would be remixed for mono. Some films shot in 35 mm, such as
Camelot, featured four-track stereophonic sound and were then
blown up to 70 mm so that they could be shown on a giant screen with six-track stereophonic sound. Unfortunately however, many of these presentations were only pseudo stereo, utilizing a somewhat artificial six-track panning method. A process known somewhat derogatorily as the
Columbia Spread was often used to synthesize Left Center and Right Center from a combination of Left and Center and Right and Center, respectively, or, for effects, the effect could be
panned anywhere across the five-stage speakers using a one-in/five-out pan pot. Dolby, who did not approve of this practice, which results in loss of separation, instead used the left center and right center channels for LFE (low-frequency effects), utilizing the bass units of the otherwise redundant intermediate front speakers, and later the unused HF capacity of these channels to provide for stereo surround in place of the mono surround.
Dolby Digital Dolby Stereo was succeeded by
Dolby Digital 5.1 in the cinema, which retained the Dolby Stereo 70 mm 5.1 channel layout, and more recently with the introduction of
digital cinema,
Dolby Surround 7.1 and
Dolby Atmos in 2010 and 2012 respectively. ==Modern home audio and video==