That move generated a great deal of publicity. Dealers in stereo phonograph equipment had no choice but to demonstrate on Audio Fidelity Records. After the release of the demonstration disc, the other spur to the popularity of stereo discs was the reduction in price of a stereo magnetic cartridge, for playing the disks, from $250 to $29.95 in June 1958. The first four mass-produced stereophonic discs available to the buying public were released in March, 1958—Johnny Puleo and his Harmonica Gang Volume 1 (AFSD 5830), Railroad - Sounds of a Vanishing Era (AFSD 5843), Lionel - Lionel Hampton and his Orchestra (AFSD 5849) and Marching Along with the Dukes of Dixieland Volume 3 (AFSD 5851). By the end of March, the company had four more stereo LPs available.

By 1968, the major record labels stopped making monaural discs.

Early broadcasting

Chicago AM radio station WGN (and its sister FM station, WGNB) collaborated on an hourlong stereophonic demonstration broadcast on May 22, 1952, with one audio channel broadcast by the AM station and the other audio channel by the FM station. New York City's WQXR initiated its first stereophonic broadcasts in October 1952, and by 1954, was broadcasting all of its live musical programs in stereophonic sound, using its AM and FM stations for the two audio channels. Rensselaer Polytechnic Institute began a weekly series of live stereophonic broadcasts in November 1952 by using two campus-based AM stations, although the listening area did not extend beyond the campus.

Tests of six competing FM-only systems were conducted on KDKA-FM in Pittsburgh, Pennsylvania during July and August 1960. The Federal Communications Commission announced stereophonic FM technical standards in April 1961, with licensed regular stereophonic FM radio broadcasting set to begin in the United States on June 1, 1961. WEFM (in the Chicago area) and WGFM (in Schenectady, New York) were reported as the first stereo stations.

Model 350, ca. 1961: the first FM multiplex stereo tuner sold in the US]]

Television: A December 11, 1952 closed-circuit television performance of Carmen, from the Metropolitan Opera House in New York City to 31 theaters across the United States, included a stereophonic sound system developed by RCA. The first several shows of the 1958–59 season of The Plymouth Show (AKA The Lawrence Welk Show) on the ABC (America) network were broadcast with stereophonic sound in 75 media markets, with one audio channel broadcast via television and the other over the ABC radio network. By the same method, NBC Television and the NBC Radio Network offered stereo sound for two three-minute segments of The George Gobel Show on October 21, 1958. On January 30, 1959, ABC's Walt Disney Presents made a stereo broadcast of The Peter Tchaikovsky Story—including scenes from Disney's latest animated feature, Sleeping Beauty—by using ABC-affiliated AM and FM stations for the left and right audio channels.

With the advent of FM stereo in 1961, a small number of music-oriented TV shows were broadcast with stereo sound using a process called simulcasting, in which the audio portion of the show was carried over a local FM stereo station. In the 1960s and 1970s, these shows were usually manually synchronized with a reel-to-reel tape delivered by mail to the FM station (unless the concert or music was locally originated). In the 1980s, satellite delivery of both television and radio programs made this fairly tedious process of synchronization unnecessary. One of the last of these simulcast programs was Friday Night Videos on NBC, just before MTS stereo was approved by the FCC.

The BBC made extensive use of simulcasting between 1974 and around 1990. The first such transmission was in 1974, when the BBC broadcast a recording of Van Morrison's London Rainbow Concert simultaneously on BBC2 TV and Radio 2. After that it was used for many other music programmes, live and recorded, including the annual BBC Promenade concerts and the Eurovision Song Contest. The advent of NICAM stereo sound with TV rendered this unnecessary.

Cable TV systems delivered many stereo programs utilizing this method for many years until prices for MTS stereo modulators dropped. One of the first stereo cable stations was The Movie Channel, though the most popular cable TV station that drove up usage of stereo simulcasting was MTV.

Japanese television began multiplex (stereo) sound broadcasts in 1978, and regular transmissions with stereo sound came in 1982. By 1984, about 12% of the programming, or about 14 or 15 hours per station per week, made use of the multiplex technology. West Germany's second television network, ZDF, began offering stereo programs in 1984.

Multichannel television sound, better known as MTS (often still as BTSC, for the Broadcast Television Systems Committee that created it), is the method of encoding three additional channels of audio into an NTSC-format audio carrier. It was adopted by the FCC as the United States standard for stereo television transmission in 1984. Sporadic network transmission of stereo audio began on NBC on July 26, 1984, with the Tonight Show—although at the time, only the network's New York City flagship station, WNBC, had stereo broadcast capability. Regular stereo transmission of programs began in 1985.

Recording methods

A-B technique: time-of-arrival stereophony

This technique can produce phase issues when the stereo signal is mixed to mono.

X-Y technique: intensity stereophony

M/S technique: Mid/Side stereophony

The left and right channels are produced through a simple matrix: Left = Mid + Side; Right = Mid − Side (the polarity-reversed side signal). This configuration produces a completely mono-compatible signal and, if the Mid and Side signals are recorded (rather than the matrixed Left and Right), the stereo width can be manipulated after the recording has taken place. This makes it especially useful for film-based projects.

Near-coincident technique: mixed stereophony

Pseudo-stereo

The special pseudo-stereo circuit—invented by Kishii and Noro, from Japan—was patented in the United States in 2003, with already previously issued patents for similar devices. Artificial stereo techniques have been used to improve the listening experience of monophonic recordings or to make them more "saleable" in today's market, where people expect stereo. Some critics have expressed concern about the use of these methods.

Binaural recording

Playback

Descriptions of stereophonic sound tend to stress the ability to localize the position of each instrument in space, but this would only be true in a carefully engineered and installed system, where speaker placement and room acoustics are taken into account. In reality, many playback systems, such as all-in-one boombox units and the like, are incapable of recreating a realistic stereo image. Originally, in the late 1950s and 1960s, stereophonic sound was marketed as seeming "richer" or "fuller-sounding" than monophonic sound, but these sorts of claims were and are highly subjective, and again, dependent on the equipment used to reproduce the sound. In fact, poorly recorded or reproduced stereophonic sound can sound far worse than well done monophonic sound. When playing back stereo recordings, the best results are obtained by using two identical speakers, in front of and equidistant from the listener, with the listener located on a center line between the two speakers. In effect, an equilateral triangle is formed, with the angle between the two speakers around 60 degrees as seen from the listener's point of view.

Vinyl records

The combined stylus motion is, in terms of the vector, the sum and difference of the two stereo channels. Effectively, all horizontal stylus motion conveys the L+R sum signal, and vertical stylus motion carries the L−R difference signal. The advantages of the 45/45 system are that it has greater compatibility with monophonic recording and playback systems. A monophonic cartridge will reproduce an equal blend of the left and right channels, instead of reproducing only one channel. Conversely, a stereo cartridge reproduces the lateral grooves of monophonic recording equally through both channels, rather than one channel. Also, it gives a more balanced sound, because the two channels have equal fidelity as opposed to providing one higher-fidelity laterally recorded channel and one lower-fidelity vertically recorded channel. Overall, this approach may give higher fidelity, because the "difference" signal is usually of low power, and is thus less affected by the intrinsic distortion of "hill and dale"-style recording.

This system was invented by Alan Blumlein of EMI in 1931 and was patented the same year. EMI cut the first stereo test discs using the system in 1933, but it was not applied commercially until a quarter of a century later. Stereo sound provides a more natural listening experience, since the spatial location of the source of a sound is (at least in part) reproduced. In the 1960s, it was common practice to generate stereo versions of music from monophonic master tapes, which were normally marked "electronically reprocessed" or "electronically enhanced" stereo on track listings. These were generated by a variety of filtering techniques to try to separate out various elements; this left noticeable and unsatisfactory artifacts in the sound, typically sounding "phased".

Compact disc

Broadcasting

Radio

Because of the limited audio quality of the majority of AM receivers, and also because AM stereo receivers are relatively scarce, relatively few AM stations employ stereo. Various modulation schemes are used for AM stereo, of which the best-known is Motorola's C-QUAM, the official method for most countries in the world that transmit in AM stereo. More AM stations are adopting digital HD Radio, which allows the transmission of stereo sound on AM stations. For Digital Audio Broadcasting, MP2 audio streams are used. DAB is one of the Digital Radio formats that is used to broadcast Digital Audio over terrestrial broadcast networks or satellite networks. DAB is extended to video, and the new format is called DMB.

Television

Common usage

Most two-channel recordings are stereo recordings only in this weaker sense. Pop music, in particular, is usually recorded using close miking techniques, which artificially separate signals into several tracks. The individual tracks (of which there may be hundreds) are then "mixed down" into a two-channel recording. By using "left-right" panning controls, the audio engineers determine where each track will be placed in the stereo "image". The end product using this process often bears little or no resemblance to the actual physical and spatial relationship of the musicians at the time of the original performance; indeed, it is not uncommon for different tracks of the same song to be recorded at different times (and even in different studios) and then mixed into a final two-channel recording for commercial release.

Classical music recordings are a notable exception. They are more likely to be recorded "live", so that the actual physical and spatial relationship of the musicians at the time of the original performance is preserved on the recording.

==Balance== Balance can mean the amount of signal from each channel reproduced in a stereo audio recording. Typically, a balance control in its center position will have 0 dB of gain for both channels and will attenuate one channel as the control is turned, leaving the other channel at 0 dB.

See also Panning.

See also

Notes

References

External links

Category:Stereophonic sound Category:Greek loanwords