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Quadraphonic sound

From Wikipedia, the free encyclopedia

Modern 4 channels Quadraphonic label
Modern 4 channels Quadraphonic label

Quadraphonic (or Quadrophonic and sometimes Quadrasonic) sound – equivalent to what is now called 4.0 surround sound – uses four channels in which speakers are positioned at the four corners of the listening space, reproducing signals that are (wholly or in part) independent of one another. Quadraphonic audio was the earliest consumer product in surround sound and thousands of quadraphonic recordings were made during the 1970s.

It was a commercial failure due to many technical problems and format incompatibilities. Quadraphonic audio formats were more expensive to produce than standard two-channel stereo. Playback required additional speakers and specially designed decoders and amplifiers.

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  • ✪ LGR - Resound OPL3: New Surround Sound AdLib Card
  • ✪ Top Tips for Setting Up Your Home For Sound
  • ✪ Quadraphonic sound
  • ✪ Upmixing Stereo To 5.1 Surround Sound In Logic Pro X
  • ✪ Santana Black Magic Woman Quadraphonic Breakdown

Transcription

Greetings and welcome to an LGR thing! And today's thing is the TexElec Resound OPL3 8-bit ISA sound card released in February of 2018 and currently costing $77.99. So yep this is yet another newly-made retro sound card with AdLib compatibility. That itself is nothing new, there are several good AdLib clones floating around these days. But the Resound has one heck of a neat gimmick that sets it apart. This not only uses the OPL3 sound chip instead of an OPL2 -- you know this was the sound chip that was really popular with tons of early 90s sound cards like the Sound Blaster 16 and compatibles -- but it also introduces, get this: four channels of OPL3 sound! That's right, surround sound AdLib is technically possible! Before we go any further this is not a sponsored video and they didn't give this to me for free or anything. I just bought it and I happen to like it. So let's talk about it! For one thing I just enjoy the visual design of this card, it's a very striking look and it's clean looking and there's a few items on it that stand out from your normal AdLib clone kind of thing. First off is this dip switch bank here for changing the base I/O address from the AdLib's default of 388h. At this point there's really not much reason to ever want to change this but the option is there in case you do. It also has a set of line level input pins up here acting as an auxiliary input in case you want to daisy-chain other sound devices. And you see all these red blocky things here? These are WIMA film capacitors, which it uses instead of your normal electrolytics, which are paired with some input and output decoupling capacitors to try and block DC noise in the audio path to get a much cleaner sounding output. It also has its own 14.31818MHz oscillator instead of just relying on the ISA bus of whatever PC you install it in. This is done to prevent any pitch-changing on select older machines with differing bus speeds than maybe the AdLib or the game expects. And of course you have two 3.5mm audio outputs one for the front left and right speakers and the other for the rear left and right. And being that this is an AdLib-compatible kind of thing the installation is quite simple. As long as you have a free 8-bit ISA slot you're good. But for the games I want to play I like using it on 486 machines like this Unisys CWD-4002 I'm installing this one in right here. And that's it for basic usage, you don't have to set up any drivers or software. If an old game is gonna look for AdLib it's gonna look for 388h, which is what this uses. So let's hit up a few of the pros of the device straight away. And for one thing there is no emulation, as I mentioned earlier this is a proper FM synth on-board: a Yamaha YMF262 OPL3 sound chip, ah! Not only is it a great chip but it has really clean output on this card, probably the best I've heard from any sound card with an OPL3 chip. Seriously it's dead silent if there's nothing playing, and all the games I tried sound just as they should. Listen to some of this stuff and enjoy! *good AdLib stuff plays for a while* *mmm, Tyrian. Sounds like OPL3 but it's using OPL2!* *doooooooooooom* *the lesser-played latter half of the Space Quest III theme* Then there's the surround sound mode which just amuses me to no end that it exists! Apparently while designing the card and researching the OPL3 datasheet they noticed a feature which does not seem to have ever been implemented on a commercial sound card back in the day. Which is that on the OPL3 chip there were two more channels beyond the usual two for stereo that are supported straight from the factory. It's worth noting this is different than what the Surround Sound Module did with the Adlib Gold card in 1992. That simply layered some reverb and echo effects on top of existing games and added simulated stereo depth to a few games that supported that, but did not have any output for separate additional sound channels and rear speakers like the Resound does. Now at this point there are no games or really anything that supports it except this one demo program that comes with the sound card itself from TexElec. But hey, it's there! So you can get your normal speakers, plug those into the front, and then two more speakers. Like, I just have some random ones here we're gonna put behind the camera. This is not a surround sound video, so it's only in stereo, it's not gonna be the best example. But yeah, just listen to this! *front left channel plays* *front right channel plays* *rear left channel plays* *rear right channel plays* Yeah there are four distinct channels all around you with AdLib sound coming out of it! That's just so cool to me, I hope that somebody does something with this in the future. And that's really the whole idea of this feature of the card: put the hardware out there and then hope that somebody in the homebrew scene does something with it. And I really hope someone does because I want to hear more things coming through and OPL3 chip all around me. It does have some cons at the moment and this is the 1.1 version of the card and hopefully some of these things will change in the future. But one of the biggest ones is that you cannot adjust the volume, either on the card or through software. And this is kind of an issue because games with FM synth and AdLib support are loud, and then soft, and everywhere in between. I mean, just look at this line out recording of these different games: they're just all over the place as far as their levels and some of them do peak a little bit. Or some are just really, really quiet. So unless the game allows you to adjust it through software you're kind of outta luck and you've just got to rely on external audio adjustment at this point in time, like some good speakers or your amplifier or something like that. But the bigger issue for me is that actually making full use of its OPL3 capability is unpredictable at best. The way you normally get OPL3 support in games is by setting it up to directly address a supported device, usually something like the Sound Blaster Pro 2 or Sound Blaster 16. The problem is that doing this with the Resound card typically won't provide anything but an error message. I'm not saying I expected this to work, I'm just pointing out one of the inherent issues in making a card with this approach. Considering there was never a standalone OPL3-only card like this manufactured back in the day, it makes sense that games don't always look for the YMF262 directly, and might rely on detecting some component or a TSR something else this card doesn't have. As a result, with games like Dune and Theme Hospital you're stuck with OPL2 support for the time being, even though games like this technically are able to support the more advanced OPL3 features that this card has. That's just with DOS though: Windows 95 and 98 are a bit of a different story, since you can just tell it to use the default AdLib Gold drivers from Windows and it shows up straight away. You still don't get any Windows volume adjustments since that would require the card to have Windows Sound System support, which it does not. But you can at least use the OPL3 as a MIDI playback device in Windows. So yeah, canyon.mid sounds pretty great! *pretty great-sounding canyon.mid file plays through OPL3 sound chip* And all this raises the question: who exactly is this card for? At $80 it still costs a whole lot less than an original AdLib card, that's for sure. But it's also on-par with or costlier than a good Sound Blaster 16 or any number of common clones from back in the day that'll be more useful to more DOS games. And as cool as the surround sound possibilities are in theory, it's not much of a selling point right now since nothing supports it yet. So I guess the Resound OPL3 is made for full-time PC geeks like me who just like to cram fresh new homebrew cards in slots and see what happens. And I'll admit, it's been a blast to screw around with for me, even with its technical setbacks and quirks. Stuff like this is just straight-up cool in my mind and it's very close to being a fantastic OPL3-based card. And as far as support for the original AdLib goes with OPL2, this is the nicest I've ever heard just because of how clean it is. So if you want a dedicated OPL2 card that just happens to have some other stuff added then this is a great choice. But at the moment it'll be sitting around while I wait for greater software and game support, especially in DOS. And if you enjoyed this look at a custom made retro device then let me know. I've got actually quite a few more of these things to cover that I haven't yet. In the meantime though there are plenty of other videos on my channel and new ones coming every Monday and Friday here on LGR. And as always thank you very much for watching!

Contents

Operation

Quadraphonic audio reproduction on vinyl records was problematic. Some systems used a demodulator to decode discrete sound channels. This allowed for full channel separation, although such systems were prone to reduced record life. Other systems used matrix decoding to recover four channels from the two channels cut on the record. Matrix systems do not have full channel separation, and some information can be lost between the encoding and decoding processes. Both discrete and matrix quadrophonic recordings could be played in two channels on conventional stereo record players.

There were less sophisticated "derived" solutions that only provided back ambience channels, not a defined placement of individual instruments.[1]

Quadraphonic systems based on tape were also introduced, based on new equipment capable of playing four discrete channels. These recordings were released in reel-to-reel and 8-track cartridge formats.

A full, four-channel (quadraphonic) system will reproduce the Left Front, Left Back, Right Front, and Right Back audio signals in each of four separate speakers. Regardless of discrete or matrix formats, in four-channel stereo the rear speakers should be of the same or almost-same size or quality and have the same or almost-same frequency range as the front speakers.

Discrete (4-4-4) formats

Discrete reproduction is the only true Quadraphonic system. As its name suggests, with discrete formats the original four audio channels are passed through a four-channel transmission medium and presented to a four-channel reproduction system and fed to four speakers. This is defined as a 4–4–4 system.

Matrix (4-2-4) formats

With Matrix formats, the four channels are converted (encoded) down to two channels. These are then passed through a two-channel transmission medium (usually an LP record) before being decoded back to four channels and presented to four speakers. To transmit four individual audio signals in a stereo-compatible manner, there must be four simultaneous linear equations to reproduce the original four audio signals at the output. The term "compatible" indicates that:

  1. A single-channel (mono) system will reproduce all four audio signals in its one speaker.
  2. A two-channel (stereo) system will reproduce the Left Front & Left Back audio signals in the Left speaker and the Right Front & Right Back signals in the Right Speaker.

The original systems (DY & EV-4) were basic and suffered from low front L/R separation (around 12db) and a poor rear L/R separation of 2db. The decoders were designed more to give an effect rather than accurate decoding, which was mainly due to limitations in both systems, although as both systems were very closely related mathematically, users only needed one decoder of either system to play back albums of both systems.

The aboves' poor decode performance was the main reason for their disappearance once the improved matrix systems arrived based on the work by Peter Scheiber. His basic formula utilized 90-degree phase-shift circuitry to enable enhanced 4-2-4 matrix systems to be developed, of which the two main leaders were Columbia's SQ and Sansui's QS Systems. With Scheiber and Martin Willcocks, Jim Fosgate developed the Tate II 101 SQ decoder, which produced a very accurate sound field by using gain riding and the  Haas effect to mask decoding artifacts. It used custom, hand-assembled and -calibrated circuitry with components sorted to 1%, for exact performance. Sansui's QSD- series decoders and QRX- series receivers were very good, even synthesizing L—R stereo into a ⋂ horseshoe topology. However, all these came too late in the game and were too expensive or difficult to procure for public purchase, to rescue matrix quad.

The differences between the original systems and the new were so large that it made it impossible to decode DY/EV-4 with either SQ or QS decoders with any accuracy, the results being just a form of artificial quad.

[2][3] This 4:2:4 process could not be accomplished without some information loss. That is to say, the four channels produced at the final stage were not truly identical to those with which the process had begun.

Derived (2-2-4) formats

Derived (2-2-4) formats were inexpensive electronic solutions that provided back ambience channels from regular stereo records. There was no deliberate placement of individual instruments on the back channels.[1]

History

Discrete tape formats

Quadraphonic open reel tape (Q4)

A 4-channel reel-to-reel tape unit from the 1970s, one of the few ways to achieve true 4-channel sound at home
A 4-channel reel-to-reel tape unit from the 1970s, one of the few ways to achieve true 4-channel sound at home

The first medium for 4-channel sound was reel-to-reel tape, used first in European electronic-music studios by 1954,[4] an outstanding example of which was the tape part of Karlheinz Stockhausen’s piece, Kontakte (1958–60), and was introduced to the American market by the Vanguard Recording Society in June 1969 as "Quadraphonic open reel tape (Q4)" tapes.[5][not in citation given] All available 4 tracks were used in one direction on the tape, running at twice the speed of the regular 4-Track reel-to-reel tapes.[6]

Quadraphonic 8-Track Tape (Q8)

RCA Records followed, in April 1970, with its announcement of a 4 channel version of the 8-track tape, named Quad-8 or Quadraphonic 8-Track Tape (later shortened to just Q8). These eventually appeared in Sept. 1970.[7] There were automobile players as well as home versions.

The format was almost identical in appearance to stereo 8-tracks, except for a small sensing notch in the upper left corner of the cartridge. This signaled a quadraphonic 8-track player to combine the odd tracks as audio channels for Program 1, and the even tracks as channels for Program 2. The format was not backward-compatible with stereo or mono players; although quadraphonic players would play stereo 8-tracks, playing quadraphonic tapes on stereo players resulted in hearing only one-half the channels at a time.

The last release in the quadraphonic 8-track format was in 1978, although most had stopped appearing by the end of 1976.

Matrix vinyl formats

Quadraphonic records did not remain restricted to the discrete-channel format used in reel-to-reel or 8-track tapes. Quadraphonic vinyl albums appeared, using several different and incompatible recording modes.

EV-4/Stereo-4 and Dynaco (DY)

The first of these were basic systems with poor performance developed by Electro-Voice (EV-4/Stereo-4) and Dynaco (Dynaquad (DY)). A so-called matrix format, it utilized four sound channels which were "encoded" into two stereo album tracks. These were then "decoded" back into the original four sound channels, but with poor decode performance that failed to match the discrete formats.

QS Regular Matrix and SQ Quadraphonic

Sansui QS sound decoder
Sansui QS sound decoder

Improved systems based on Peter Scheiber's work on utilizing 90-degree phase-shift circuitry came later, namely the QS and SQ systems.

The first of these, known as QS, was developed by Sansui Electric. A so-called matrix format, it utilized four sound channels, which were "encoded" into two stereo album tracks. These were then "decoded" back into the original four sound channels. The QS system debuted in the United States in March 1971 and was improved by their Vario-Matrix system in 1973.[citation needed]

The second, SQ, was developed and marketed by Columbia Records and Sony and entered the US market in April 1971. The SQ format was also used by companies such as EMI in Great Britain, who pressed several SQ album releases. The sound separation of the SQ system was greatly improved by the introduction of SQ Full Logic decoding in 1975 using the Motorola chips MC1312, MC1314 & MC1315.[citation needed]

Discrete vinyl formats

CD-4 or Quadradisc

An RCA Quadradisc record
An RCA Quadradisc record

The third major format for 4-channel vinyl LPs, known as CD-4 or Quadradisc, was devised by the Japanese JVC Corporation along with its United States counterpart RCA Records.

This quadraphonic format was first marketed in the United States in May 1972. A fully discrete sound mode, it eschewed the previous matrix systems in favor of a more complex method of 4-channel reproduction.[citation needed] It encoded surround information in ultrasonic sound above 20Khz, requiring a special cartridge with a Shibata stylus, then used its own demodulator and decoder to retrieve the original sound field.

UD-4 / UMX / BMX

UD-4/UMX was developed by Nippon/Columbia (Denon). This is a hybrid discrete/matrix system. Only 35 to 40 items are encoded in this format and it was marketed only in the UK, Europe, and Japan.

The system suffered from incompatibility with regular stereo playback due to phase differences between the left and right channels.[8]

UD-4 was less critical in its setup than CD-4 because the carriers did not have to carry frequencies as high as those found in the CD-4 system.[9]

Radio broadcast formats

There were some experiments done with radio broadcasts (e.g., a Cliff Richard concert by the BBC,[10][11] whose earliest quadraphonic broadcast was in July 1974[12]), but they were short-lived.

One radio series, Double Exposure, was briefly syndicated throughout the United States to various FM stations; it was made up of jazz, rock and pop music that had been commercially released in one of the quadraphonic record or tape systems.

One of the longest-lived radio broadcasts was WQSR-FM "Quad 102½" in Sarasota, Florida.[13] Throughout most of the 1970s this station broadcast a signal which could be tuned as two separate stations with conventional stereo receivers.

In addition, San Francisco classical music station KKHI broadcast the San Francisco Opera in "compatible" (that is, matrix-encoded) quadraphonic format during the 1970s, as did Chicago station WFMT's live "Chicago Lyric Opera" broadcasts.[citation needed].

KRMH-FM ("Good Karma Radio")(San Marcos/Austin, Texas) broadcast in "Quad Stereo" in the early 1970s from its studios and transmitter near Buda, Texas.[citation needed]

KEXL-FM ("KEXL 104.5") (San Antonio, Texas) broadcast in "Quadraphonic" in the early to mid 1970s from its studios in a high-rise office building off Main Plaza. [14]

Sacramento station KWOD 106.5, named after the format, broadcast briefly beginning in 1977.

Regional station of Polskie Radio in Wroclaw had two experimental broadcasts a week at the end of the 1970.

Matrix H

Ambisonic mixing equipment
Ambisonic mixing equipment

Matrix H was developed by BBC engineers to carry quadraphonic sound via FM radio in a way that would be most compatible with existing mono and stereo receivers.[15]

Quadraphonic test programmes were made for BBC Radio 3 and BBC Radio 4, including plays and The Proms.[16]

The existing matrix formats were tested first. The "H" has no meaning; they called the first matrix assessed Matrix A, and then worked through the alphabet.[17][18] Matrix H emerged as the best solution for mono compatibility and radio transmission,[19] yet there was no specific commercially available decoder for it.

The BBC later cooperated with the developers of Ambisonics to produce BBC/NRDC System HJ. This was based on tolerance zones designed to include modified versions of both Matrix H and the prototype two-channel encoding of Ambisonics, known as System 45J. Subsequently, the Nippon-Columbia UMX matrix was brought into the standard, leading to the final UHJ name now associated with Ambisonics.[20]

Universal SQ

In 1976, Ben Bauer integrated matrix and discrete systems into USQ, or Universal SQ (others had done this with their quad systems too).

It was a hierarchical 4-4-4 discrete matrix that used the SQ matrix as the baseband for discrete quadraphonic FM broadcasts using additional difference signals called "T" and "Q". For a USQ FM broadcast, the additional "T" modulation was placed at 38 kHz in quadrature to the standard stereo difference signal and the "Q" modulation was placed on a carrier at 76 kHz.

For standard 2-channel SQ Matrix broadcasts, CBS recommended that an optional pilot-tone be placed at 19 kHz in quadrature to the regular pilot-tone to indicate SQ encoded signals and activate the listener's Logic decoder. CBS argued that the SQ system should be selected as the standard for quadraphonic FM because, in FCC listening tests of the various four channel broadcast proposals, the 4:2:4 SQ system, decoded with a CBS Paramatrix decoder, outperformed 4:3:4 (without logic) as well as all other 4:2:4 (with logic) systems tested, approaching the performance of a discrete master tape within a very slight margin. At the same time, the SQ "fold" to stereo and mono was preferred to the stereo and mono "fold" of 4:4:4, 4:3:4 and all other 4:2:4 encoding systems.

Live concerts

Azimuth Co-ordinator used by Pink Floyd, made by Bernard Speight, 1969 (Victoria & Albert Museum, London)
Azimuth Co-ordinator used by Pink Floyd, made by Bernard Speight, 1969 (Victoria & Albert Museum, London)

In 1967 the rock group Pink Floyd performed the first-ever surround-sound rock concert at “Games for May”, a lavish affair at London’s Queen Elizabeth Hall, where the band debuted its custom-made quadraphonic speaker system.[21] The control device they had made, the Azimuth Co-ordinator, is now displayed at London's Victoria and Albert Museum, as part of their Theatre Collections gallery.[22]

Format comparisons

In 1976, Mike Thorne created the vinyl album Quadrafile, with the same music recorded on all four sides, but in four different quadraphonic formats (QS, SQ, CD-4, and UD-4).

Current situation

The rise of home theatre products in the late 1980s and early 1990s brought multi-channel audio recording back into popularity, although ultimately in new digitally based formats. Many of the 1970s quadraphonic recordings have been reissued in modern surround sound systems such as DTS, Dolby Digital, DVD-Audio and Super Audio CD.

See also

References

  1. ^ a b Popular Science, p. 86, at Google Books
  2. ^ Scheiber, Peter (December 1969). "Toward a More Accurate Spatial Environment". Journal of the Audio Engineering Society. AES. 17 (6): 690, 691.
  3. ^ Scheiber, Peter (November 1971). "Analyzing Phase-Amplitude Matrices". Journal of the Audio Engineering Society. AES. 19 (10): 835–839.
  4. ^ Cross, Lowell, "Electronic Music, 1948–1953", Perspectives of New Music 7, no. 1 (Autumn–Winter, 1968): 32–65. Citation on 50–51.
  5. ^ http://www.obsoletemedia.org/quadraphonic-open-reel-tape/
  6. ^ http://theartofsound.net/forum/showthread.php?1929-The-Official-Factory-Made-Reel-to-Reel-Tape-Thread&s=277907ddc0421c90b538c564d5d4f18f
  7. ^ http://www.ladydairhean.0catch.com/Axl/Guides/MFG2.htm
  8. ^ Cooper, Duane. "THE UD-4 SYSTEM". HI-FI NEWS & RECORD REVIEW - MARCH 1975. Retrieved 5 February 2012.
  9. ^ Cooper, Duane H.; Shiga, Takeo (June 1972). "Discrete-Matrix Multichannel Stereo" (PDF). Journal of the Audio Engineering Society. AES. 20 (5): 346–360. Retrieved September 28, 2018.
  10. ^ "Cliff Richard". BBC Genome at BBC Online. Retrieved 18 November 2014.
  11. ^ "Cliff Richard". BBC Genome at BBC Online. Retrieved 18 November 2014.
  12. ^ "BBC in quad". BBC Genome at BBC Online. Retrieved 18 November 2014.
  13. ^ Radio Years.com
  14. ^ http://www.penningtontechnicalarts.com/KEXL/
  15. ^ "Archived copy". Archived from the original on 2014-12-11. Retrieved 2014-09-21.CS1 maint: Archived copy as title (link)
  16. ^ Ratcliff, P.A.; Meares, D.J. (May 1977). "BBC Matrix H: Compatible system for broadcasting". Wireless World: 41–45.
  17. ^ Crompton, T.W.J. (November 1974). "The subjective performance of various quadraphonic matrix systems" (PDF). BBC Research Department Report 1974/29.
  18. ^ Gaskell, P.S.; Ratliff, P.A. (February 1977). "Quadraphony: Developments in Matrix H decoding" (PDF). BBC Research Department Report 1977/2.
  19. ^ Quadraphonic Systems
  20. ^ N.R.D.C. Ambisonic Technology (22 November 1977). "Encoding Standards for NRDC Universal HJ Surround-Sound Encoding System: "System UHJ"" (NRDC/FCC 2). National Research Development Corporation. NRDC/FCC 2.
  21. ^ Wired, May 12, 1967: Pink Floyd Astounds With ‘Sound in the Round’, May 12, 2009
  22. ^ "pink floyd". Archived from the original on 2009-03-18. Retrieved 2009-08-14.

External links

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