Quadrophonic Sound

[jabba17]

On at least one Saturday afternoon in about 1972, WZGC and WREK broadcast discrete quadraphonic sound, the front channels on WGZC and the rear channels on WREK. I was not that impressed. There was never any method proposed for discrete 4-channel on a single station.

I seem to remember that WQXI-FM claimed to be broadcasting in the SQ matrix format (developed by Sansui) at one time in the mid/latter '70s. The matrix encoders "tried" to encode 4 channels into 2, but the separation was almost nil. 90 degree phase shift circuits were used to attempt to create a directional sound field. The more advanced matrix decoders had agc expander circuits that used "logic" to automatically vary the gain of the channels in an attempt to artificially enhance the separation.

The Quadradisk, developed by JVC (and maybe RCA), was the only true discrete 4-channel LP, but few records were issued in the format. Playback required a complex decoder and a special phono cartridge. The matrix-encoded disks required no special cartridge, but a decoder was required for playback. At one time, CBS announced that all of its LPs would be SQ matrix-encoded quad disks.

Any FM station could claim that it was broadcasting in quad simply by playing the quad-matrix discs, no encoder required - a trick probably used by many broadcasters.

SQ was CBS, QS was Sansui.

JVC (Victor Co. of Japan) was the Japanese affiliate of RCA, so there was a lot of technology sharing (RCA and WEA used Quadradisc). In fact, JVC has the rights to the Nipper "His Master's Voice" logo in Japan to this day.

Quadradisc encoded and recorded the two left and right difference (front minus rear) signals at much higher frequencies than the two left and right sum (front plus rear) signals (similar to how the difference signal is encoded for FM stereo, with a mono sum signal and an encoded left minus right difference signal). The upside was four quasi-discrete channels (well, more "discrete" than a matrixed setup--not as truly discrete as 4 separate signals) with excellent separation compared to matrix formats. Downside was poor high-frequency response on the sum signals (due to the sharp rolloff required to separate the sums from the differences), and the tendency of non-quad styli to abusively "wear off" the high-frequency difference signals from the grooves with repeated play.

Of course, there would be no way to transmit or recover a quad signal from a Quadradisc recording over FM, with FM's sharp rolloff obliterating Quadradisc's difference signals to make room for FM stereo's difference signal.

 

[jabba17]

Apparently a standard for quad broadcasting on FM was adopted by the FCC, that was backwards-compatible with both mono and stereo receivers:

http://en.wikipedia.org/wiki/FM_stereo#Quadraphonic_FM

It also sounds like the adoption of quad FM went just like that of AM stereo, with the same results, with the FCC approving a standard too late in the game to matter (in quad's case, by the time the standard was approved, the quad fad had run its course).

 

[RTibbs]

As someone else said this same conversation will be had in a few years about HDRadio. Too late for the oncoming advent of streaming your stations once wifi becomes omnipresent.

 

[RoddyFreeman]

As someone else said this same conversation will be had in a few years about HDRadio. Too late for the oncoming advent of streaming your stations once wifi becomes omnipresent.

Wouldn't quadraphonic sound be the same as Jorday Graye coming out of 2 speakers and Kate McCarthy coming out of the other 2?

 

[jabba17]

As someone else said this same conversation will be had in a few years about HDRadio. Too late for the oncoming advent of streaming your stations once wifi becomes omnipresent.

The same could be said for satellite, too. Although satellite will hang on as a niche product in locations and applications where wireless broadband has poor penetration.

 

[RTibbs]

As someone else said this same conversation will be had in a few years about HDRadio. Too late for the oncoming advent of streaming your stations once wifi becomes omnipresent.

The same could be said for satellite, too. Although satellite will hang on as a niche product in locations and applications where wireless broadband has poor penetration.

Sure but at least satelite received some mass reception the rest were fads that never caught on.