Quadraphonic sound

Quadraphonic (also: quadraphonic or Vierkanalstereofonie ) is a technology developed in the 1970s, the form of multi-channel recording and playback, which was found mainly between about 1969 and 1980. Although they did not achieve widespread use, however, is important as a precursor of today's technology Dolby Surround technology and their successors, as well as surround sound with 5.1 - channel configuration.

History

Mid -1960s to stereo slowly began to prevail against Mono. The company Philips has developed the first compact cassette devices as voice recorders. The first devices for music were also in mono, soon sat analogous to the record, when the tape recorders rapidly through stereo. Many boards still appeared simultaneously in stereo and mono. Beginning of the 1970s was the time of the mono- record in the consumer sector slowly. In the field of radio station held the mono- page promo pressings until the mid -1980s.

The market was mainly in Hi-Fi on the lookout for something new. This was found in the quadraphonic, one was convinced. The problem with this was the transferability from the studio to the end consumer. While the tapes, the multi-channel capability could be realized simply by adding more tracks and only by the width of the tape found its limits, this was difficult in the record with their only two sides of the groove. But the 4-track tapes for the home were at 4 -channel Bespielung inconveniently only in one direction playable.

Wrong assumption

Always there are very different opinions such as:

All quadraphonic systems are based on the false assumption that a sound field by recording four channels and playback four speakers in a 90 ° arrangement could be reproduced each other. In such an arrangement, however, gaps in the sound field. Better recording and reproduction of spatial sound field can be achieved with other imaging techniques, such as the Ambisonics system, which was proposed in 1972 by Michael Gerzon to date, but could not bring significant economic success.

Quadraphonic, as well as stereo surround sound systems and other, based on the effect of the phantom source. If you sit in an equilateral triangle with two speakers, does the phantom source. If you turn around with his back to the speakers, the localization in the width of the sound source is significantly reduced. If you turn sideways to the speakers, then the localization of lateral auditory events from direct signals appear very stable.

When one shuffles quadraphonic phantom sources for four square, that is, with an angular distance of 90 ° from one another are arranged in each case between adjacent speaker speakers. It follows that the audience inevitably has a pair of speakers in the back, and each have a pair to the sides. As you know, but that phantom sound sources only work from the front ( and, strictly speaking, only at an angular distance of the speakers from a maximum of about 60 °), it is obvious that quadraphonic can not work.

Hearing test at that time, as well as the later distributed worldwide DOLBY 5.1 technology, however, show that phantom sound sources can certainly help. But of course it remains to be transferred to another acoustic environment in the control room a try. DOLBY 5.1 supplemented actually for quadraphonic only important for movies (especially under adverse listening conditions ) center speaker for clear localization middle of the picture.

Technical procedures and their dissemination

Called True quadraphonic ( 4-4-4 system ), and discrete quadraphonic

The four audio channels separately on the entire signal path. For each Tonträgerformat quadro -enabled players are required: CD4 procedures for record players (see below), 8-track tape deck, tape recorders with at least four simultaneously usable tracks. For the transfer of four discrete (not matrixed ) audio channels via VHF radio, there is no feasible solution ( that would only be possible through the use of two VHF channels and two FM radio receivers ).

Early to mid -1970s, has been developed intensively in the quadraphonic technology and also sold. The JVC was in this area as a leader. JVC developed a way to keep the front two channels compatible with the normal stereo channels and only the back two to transfer using a converter into the inaudible range and retrieve again for vinyl LPs.

This was achieved by developing a special diamond pulp refiner in the pickup which could also pick up sounds inaudible to humans in the area of the plate. The two rear channels were transferred before the production of the record from the normal audible range of 20 Hz to 20 kHz to 30-60 kHz and brought back into the audible range after sampling the needle through the converter again. This technique has been marketed under the name of CD4 and the only true quadraphonic method. CD4 does not count with the four discrete channels so that the usual " matrix method " with only two transmission channels.

JVC was also the largest provider of quadraphonic amplifiers. The introduction of a quadraphonic Compact Cassette to the veto of the company Philips, the patent holder, have failed because, although the cassette format would have been compatible with the normal cassette tape with former technology would have been only in one direction loaded and playable.

For audio CD, a quadraphonic format was defined in the Red Book standard, there was never, however, CDs and players for it. Today, there are CDs in DTS.

Matrix quadraphonic ( 4-2-4 system )

The four channels are encoded using complex mathematical and electronic procedures taking advantage of phase differences in two stereo channels and decoded again during playback. Conventional stereophonic players can be retained ( ie, the system is backward-compatible ), it will only require a decoder and associated 4 -channel amplifier with speakers. Thus, reproduce matrix- encoded stereo Quadrofonieaufnahmen each capable Tonträgerformat; a dissemination via VHF radio is nothing in the way. In part, send radio station even " accidentally " Quadraphonic when they send a matrix- encoded disk recording. The disadvantage of this method is that the front-to - channel separation not work as well as the discrete process, and that the channels are actually defined below, whereby the phantom signal can arise. At that time, emerged at the same time several, not mutually compatible matrix encoding. These methods competed with each other (much like in the video section VHS, Betamax and Video2000 ); many potential buyers bought none of the systems, because they were afraid to opt for one that would not prevail and for which one then no recordings would be able to buy.

The later used in the film industry Dolby surround system uses the same approach.

Quadraphonic recordings for the matrix technique based on the direction of dominance circuit and on so-called " Quadro records " (SQ, QS, RM ), tape or 8 track tape (Q8 ) were recorded.

The quadraphonic, etc. could never prevail on a larger scale due to competing and non-compatible technological matrix Quadro systems such as SQ, QS, UD4, EV 4, QM, UMX.

The problem of proliferation was also by the fact that in the early 1970s, when the quadraphonic propagated by various audio manufacturers, audio systems were very expensive. It was many listeners not possible to keep up with the sequence of appearing innovations. The majority of the recordings were then mixed in stereo and was therefore not suitable for quadraphonic. The stereo recordings could only be played in " Pseudoquadrophonie ".

Pseudoquadrofonie ( 2-2-4 system )

As Pseudoquadrofonie is called two-channel stereo playback recordings via four speakers or groups of speakers.

This type of playback time was the most common dar. Many providers, for example, Dual, Marantz, Pioneer and Scan -Dyna, brought " Quadro adapters" on the market. Most of them just split up the signal in different speakers: the difference between the left and right audio channel was routed to the rear speakers and it turned one of those speakers in phase.

When the recordings were accidentally or intentionally suitable for Pseudoquadrofonie, only the sound sources were located from the rear, which is also at a musical performance in a concert hall listening from behind, such as reverb and applause from the audience. In many cases Pseudoquadrofonie deteriorated the sound significantly, similar to the attempts to imitate the real Pseudostereofonie Stereofonie.

Marantz even worked with quadraphonic tape deck, who divided the signal with a so-called pan controls and with different strengths of signals initiated at the main and Rearspeakers. Also this was not a "real " quadraphonic.

Four channel at the movies

Ray Dolby and his company (known for noise suppression method for magnetic sound recording, including Dolby B, Dolby C, Dolby S and Dolby HX Pro ) introduced in 1974 Dolby Stereo. Dolby Stereo was a multi-channel audio system that can encode four channels (left, center, right, rear) on a two-channel stereo track. In the cinema the four channels are decoded from the two channels of the stereo sound with a decoder again. Thus, a cost-effective introduction of surround sound was possible. Existing film projection systems could be retrofitted with a Dolby stereo decoder.

Newer methods

Quadraphony is a precursor technology of Dolby Surround system, which was based on the matrix method of quadraphonic, and the current digital 5.1, 6.1 and 7.1 surround sound method.

However, these methods were able to assert themselves only when the trend from " enjoying music " remote and its focus on the " home cinema " shifted. The reproduction of sounds and voices, subject to ( subjectively) a different geographic location behavior and is thus " easier " distributed among multiple channels.

Comparison of the method, historically and currently

The four channels of quadraphonic not based on only about four receiving channels or microphones, but there are initially recorded raw footage on part 30 tracks on which the various instruments or orchestral or vocal groups are recorded as stereo or surround sound current method. For example, in each channel has a different group of instruments resound. Only four microphones are used for Quadro - shots at best in the amateur field. Only then follows the creative part of the mix, which is mixed in stereo to two and Quadro on four channels. In current surround sound formats with 5.1 or more channels will act accordingly. The surround sound field of discrete quadraphonic is therefore just as stable as the current surround sound method. Then are the four discrete Quadro channels, is ever encoded on the system, whereby the matrix systems reduced to two channels (eg SQ and QS) (together with the "hidden" other- rear channels ) and for further discrete CD4 system to record the difference signals are stored to the stereo compatible mixture in the audible range on a 30 - kHz carrier signal. Decoded is then mirrored matrix circuits (decoder ) or CD4 with demodulators, with a "simple" A / B matrix then sorted apart front and rear. While the matrix systems initially only a small crosstalk attenuation had front - rear ( 3-12 or max. 20dB ) was, immediately reaches a channel separation of 30 dB at CD4. This channel separation is even surpassed today by the fully digital systems.

The distribution of the sound field in the quadraphonic into equal 90 ° sectors allows (but only in theory, as explained above ) both ( with discrete playback) homogenous sound reproduction and a location with the same conditions for all directions. The dominant rather forward new 5.1 - or - more - sound source locations of the focus rather is on the playback of sound effects, which has to do with a homogeneous or uniform all-round sound field rather little. The use of eight or more speakers primarily is designed for cinemas, where yes 90 % of the audience not on acoustically optimal space for phantom sound images sitting, and is therefore only an auxiliary solution. Four channels should be sufficient to map a 360 - room, at least in the so-called "sweet spot".

One considers, however, the detailed comparisons of the different multi-channel systems, such as ( made ​​famous by electronic adaptations of classic works and a pioneer of quadraphonic earlier as Walter Carlos ) explains Wendy Carlos on her website, it is clear that the limitations of the 4-channel technique of 70s of the 20th century brought not only by the most widely used matrix technique ( separation of the channels during playback was insufficient with the analogue technology of the time, because due to the phase relationships of the channels were each phantom sound images between the rear speakers and between front and rear possible), but also by the aforementioned false 90 ° positioning of the speakers. Because: The ear is constructive for spatial perception from the front and designed from the side (note the orientation of the pinna). If you want to create effects such as sound just behind the head, or even the fact you have to use psychoacoustic techniques (so to speak Virtual Surround with four or more channels).

It has been shown that this (even with old discrete Quadro Recordings ) works best when the front speakers as stereo usual with about 60 ° angular distance from each other and the surround speakers at the side to your ear ( so to turn about 60 ° angular distance to the front speakers ) are situated, namely all approximately the same distance from the listener. Then disappear the spatial gaps in the anterior or lateral area and the area behind the listener is generated by psychoacoustic effects.

In summary, there have been a variety of matrix- based and discrete multi-channel systems that have been enhanced to compensate for unfavorable geographical conditions and listening positions over time to other speakers. To play an acoustic 360 ° area must include at least four equivalent (!) Speakers, the " rear " should actually be placed laterally of the listener. Preference should be given to all cases discrete sound sources, classical CD4, Q8, Spulentonbänder, modern DVD-A, SACD and DTS. Dolby Digital is conceptually inferior for pure audio reproduction because it was developed for the cinema. All Matrix systems use phase shifting and mixing of the output channels, which are then to be separated only with proper effort again. There are, however, considerable advancements such as DTS Neo: 6 and Dolby ProLogic II, which use for decoding a digital signal processor. Theoretically, such a processor for old matrix-encoded Quadrofonieaufnahmen conceivable, but the effort is out of proportion to the benefit, because now, thanks to the widespread use of multi-channel systems many historical quadraphonic recordings will be revived by re-releases on modern recordings.

Known Quadrofoniealben

Between 1970 and 1980 complete albums appeared repeatedly in quadraphonic, especially reissues already successful albums more famous artists. The following list is not complete, but only shows a selection of one, irrespective of the method, narrow program.

  • Black Sabbath - Paranoid
  • John Lennon - Imagine
  • Mike Oldfield - Tubular Bells
  • Mike Oldfield - Exposed
  • Pink Floyd - Atom Heart Mother
  • Pink Floyd - The Dark Side of the Moon ( This also an Australian as special edition in pink colored vinyl exists: the combination of quadraphonic and colored vinyl is extremely rare. )
  • Pink Floyd - Wish You Were Here
  • Rick Wakeman - The Myths and Legends of King Arthur and the Knights of the Round Table
  • Herbert von Karajan - Beethoven: the complete symphonies
  • Kraftwerk - Autobahn
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