Quadraphonic Broadcast Transmitting Equipment

[kfbkfb]

Broadcasters were concerned about the unique problem of CD-4 discs to air:
the "silent" sections between songs aren't silent on CD-4 discs,
the carrier is still there, the spin up would produce something audible rather
than being a silent spin up.

IIRC, RCA came up with a filter for this problem (seems to me like an impossible
to solve problem). I'll try to find this article and scan/post it here.

Upgrading the broadcast tape cartridge system to record/play 4 tracks/channels
seems like a much more practical solution.


Kirk Bayne

 

[Owen Smith]

Seems to me the simple solution for the radio stations would have been to transfer CD-4 records ONCE to quad tape, and then played the tapes. That would allow the transfer to be done with the care required, potentially off site and even by a third party. They could also mute the gaps between tracks.

 

[Soundfield]

Seems to me the simple solution for the radio stations would have been to transfer CD-4 records ONCE to quad tape, and then played the tapes.

Sure, why not add yet another couple of stages of audio degradation to this tortuous signal path - it long since stopped making any sense from a hi-fi point of view!

 

[gvl_guy]

What's so sad is that with today's new technology, quad would have been easy with digital broadcasting. When it was developed, they could have built in the 4 channel discrete. But, as with anything, woulda coulda shoulda.

 

[Soundfield]

What's so sad is that with today's new technology, quad would have been easy with digital broadcasting. When it was developed, they could have built in the 4 channel discrete.

It wouldn’t have helped much though, the problem goes much deeper than that.

Quad didn’t really fail due to the format wars. It failed because as a concept it was fundamentally flawed and the public soon noticed that none of the formats, however complex and expensive, didn’t actually deliver on the promise. Manufactures and record producers rushed into the arena with the simple belief that stereo works well, so if we just add another couple of speakers we can create three more stereo images to the sides and to the rear of the listener – voila! – perfect surround sound! Strange that no one spotted at the time that’s not how human hearing actually behaves! Or perhaps they thought they’d just get away with it.

The consequence being that even if you have four genuinely discrete channels from four microphones to four speakers it’s not really dramatically lifelike, and even then the ‘sweet spot’ is tiny – have you ever heard such a demo? - I think you’d be underwhelmed. And that was the benchmark, the very best all the formats were striving to achieve! The industry promised a level of performance “double stereo” quad was intrinsically never capable of delivering. The public expected a quantum leap akin to the improvement in going from mono to stereo or from B/W to colour TV. It was never going to happen. It wasn’t that it didn’t work very well, it couldn’t.

Regardless of the carrier technology (tape, matrix disc, “discrete” disc etc.) simple four channel reproduction of itself is incapable of adequately fooling the brain. That requires a system that employs proper modelling of the way human hearing works and mapping it onto a suitable reproduction technique. The depth of understanding of the behaviour of the ear-brain system and of psychoacoustics is still being developed to a level where something approaching genuine realism is possible. But there’s still a lot to do and, incidentally, simply throwing ever more channels at the problem is a fool’s errand.

My quad records still make a nice noise though.

 

[atrocity]

Upgrading the broadcast tape cartridge system to record/play 4 tracks/channels
seems like a much more practical solution.

That was my first thought as well. There's no shortage of precedent for stations to be run 100% off carts back then.

 

[atrocity]

Sure, why not add yet another couple of stages of audio degradation to this tortuous signal path - it long since stopped making any sense from a hi-fi point of view!

In my home town there were at least two stations doing that full-time anyway. From a hi-fi point of view, the tape was the least of the problem.

 

[par4ken]

I

It wouldn’t have helped much though, the problem goes much deeper than that.

Quad didn’t really fail due to the format wars. It failed because as a concept it was fundamentally flawed and the public soon noticed that none of the formats, however complex and expensive, didn’t actually deliver on the promise. Manufactures and record producers rushed into the arena with the simple belief that stereo works well, so if we just add another couple of speakers we can create three more stereo images to the sides and to the rear of the listener – voila! – perfect surround sound! Strange that no one spotted at the time that’s not how human hearing actually behaves! Or perhaps they thought they’d just get away with it.

The consequence being that even if you have four genuinely discrete channels from four microphones to four speakers it’s not really dramatically lifelike, and even then the ‘sweet spot’ is tiny – have you ever heard such a demo? - I think you’d be underwhelmed. And that was the benchmark, the very best all the formats were striving to achieve! The industry promised a level of performance “double stereo” quad was intrinsically never capable of delivering. The public expected a quantum leap akin to the improvement in going from mono to stereo or from B/W to colour TV. It was never going to happen. It wasn’t that it didn’t work very well, it couldn’t.

Regardless of the carrier technology (tape, matrix disc, “discrete” disc etc.) simple four channel reproduction of itself is incapable of adequately fooling the brain. That requires a system that employs proper modelling of the way human hearing works and mapping it onto a suitable reproduction technique. The depth of understanding of the behaviour of the ear-brain system and of psychoacoustics is still being developed to a level where something approaching genuine realism is possible. But there’s still a lot to do and, incidentally, simply throwing ever more channels at the problem is a fool’s errand.

My quad records still make a nice noise though.

I totally disagree with you, while stereo (2 channels) to me is only a slight improvement over mono, quad (even synthesized) is the only way to listen to music!!!!!

 

[Soundfield]

I totally disagree with you, while stereo (2 channels) to me is only a slight improvement over mono, quad (even synthesized) is the only way to listen to music!!!!!

Yes its very pleasant and often great fun. But much more accurate? Much more realistic? Honestly, disappointingly, no.

 

[MidiMagic]

Once I started listening in quad, I never stopped listening in quad.

A few facts:

1. The quad listener notices mainly two main separations:
- Center front to center back
- Left front to right front.
I verified this with my equipment.

2. Two systems use the above two main separations as their main points of separation:
- The Dynaco Diamond
- Dolby Surround
They sound better to me than any of the 4-corners systems.

3. Most of the quad reel-to-reel recorders were not going into quad systems. They were going into home studios as multitrack decks. I repaired several quad decks when I was repairing home electronics, and all of the ones I saw were in studios. I have two and they are used for track collection, not quad.

4. Dolby surround does solve the side and back imaging problem. I have been able to smoothly pan a sound all the way around the room with no sudden jumps or vague localizations.

 

[stevendive]

It wouldn’t have helped much though, the problem goes much deeper than that.

Quad didn’t really fail due to the format wars. It failed because as a concept it was fundamentally flawed and the public soon noticed that none of the formats, however complex and expensive, didn’t actually deliver on the promise. Manufactures and record producers rushed into the arena with the simple belief that stereo works well, so if we just add another couple of speakers we can create three more stereo images to the sides and to the rear of the listener – voila! – perfect surround sound! Strange that no one spotted at the time that’s not how human hearing actually behaves! Or perhaps they thought they’d just get away with it.

The consequence being that even if you have four genuinely discrete channels from four microphones to four speakers it’s not really dramatically lifelike, and even then the ‘sweet spot’ is tiny – have you ever heard such a demo? - I think you’d be underwhelmed. And that was the benchmark, the very best all the formats were striving to achieve! The industry promised a level of performance “double stereo” quad was intrinsically never capable of delivering. The public expected a quantum leap akin to the improvement in going from mono to stereo or from B/W to colour TV. It was never going to happen. It wasn’t that it didn’t work very well, it couldn’t.

Regardless of the carrier technology (tape, matrix disc, “discrete” disc etc.) simple four channel reproduction of itself is incapable of adequately fooling the brain. That requires a system that employs proper modelling of the way human hearing works and mapping it onto a suitable reproduction technique. The depth of understanding of the behaviour of the ear-brain system and of psychoacoustics is still being developed to a level where something approaching genuine realism is possible. But there’s still a lot to do and, incidentally, simply throwing ever more channels at the problem is a fool’s errand.

My quad records still make a nice noise though.

Would you, by any chance, be alluding to something based on spherical harmonic decomposition?

 

[Soundfield]

Would you, by any chance, be alluding to something based on spherical harmonic decomposition?

Not as such, although I suspect ultimately some such advanced form of microphone array would have to be part of the solution, as you obviously know, Ambisonics recognised that with the adoption of tetrahedral array. The trouble is I don't know what its reciprocal form at the reproducing end would look like practically.

 

[stevendive]

Not as such, although I suspect ultimately some such advanced form of microphone array would have to be part of the solution, as you obviously know, Ambisonics recognised that with the adoption of tetrahedral array. The trouble is I don't know what its reciprocal form at the reproducing end would look like practically.

Ambisonics itself has moved on a long way beyond the relatively simple 1st order one, of which most people are aware, by extension to higher orders.

In principle, ambi’s angular resolution, over the sphere or horizontally, is unlimited. In practice, going to 5th order seems to be what many are working with and 3rd order very common. Recent research has suggested 3rd order gives excellent sense of depth, meaning a realistic number of channels and loudspeakers, though I can’t imagine many people having an extensive dome of speakers in their home listening rooms.

At the moment, ambisonics is limited to the VR world, where it’s in general use. Maybe eventually it will make its way back into more general use.

 

[kamranv]

The free software that we made (with a lot of help) could help you to broadcast QS. Check out this post to get the info:::: SQ/QS Matrix Decoding Software

As stated in other replies matrix encoding works over FM. Folks on this very forum could hear your broadcast through all of their excellent vintage equipment and of course the best experience is the involve decoder.

Also, it’s not perfect but pretty much every receiver built from 2001 to now has dolby pro logic II in it. People can use “music mode” to listen to your broadcast. It’s a pretty massive install base and most people don’t even know it’s possible.

Hello Everyone, with a grant from the National Endowment for the Arts and dublab we just did a national call for NEW quadraphonic work. If you make music or know people who do we would love to hear your work. There are lots of incredible people involved too:

#MakeMusicinSpace at http://QUARK.CyKiK.com with dublab's national call for your #quadraphonic work reviewed by Suzanne Ciani, Laura Escudé, Laraaji, Craig Leon, and Timeboy. The chosen applicant receives a $500 honorarium & creative tools from Ableton, The Cargo Cult, FabFilter, Focusrite, iZotope, Moog Music Inc., Output, Pioneer DJ, Spitfire Audio, The Transmute Academy. Made possible by a grant from the National Endowment for the Arts.

 

[jaybird100]

Both CBS (SQ) and Sansui (QS) sold encoders to broadcast stations to matrix encode discrete four channel tapes into a compatible stereo form for broadcast. The encoders could also synthesize a stereo source to playback much like an actual encoded record would, stations could claim to be broadcasting quad continuously.
A discrete system was proposed by Lou Dorran and others using what was the SCA subcarrier in addition to the regular subcarrier used for stereo. Interest in Quad died out before a discrete system could be adopted.

The Dorren System remains authorized by the FCC, if any station chooses to employ it. It did, as you say, come on the scene too late. Interest in quad was waning, and it's doubtful it would have made a difference.

 

[par4ken]

Once I started listening in quad, I never stopped listening in quad.

A few facts:

1. The quad listener notices mainly two main separations:
- Center front to center back
- Left front to right front.
I verified this with my equipment.

2. Two systems use the above two main separations as their main points of separation:
- The Dynaco Diamond
- Dolby Surround
They sound better to me than any of the 4-corners systems.

3. Most of the quad reel-to-reel recorders were not going into quad systems. They were going into home studios as multitrack decks. I repaired several quad decks when I was repairing home electronics, and all of the ones I saw were in studios. I have two and they are used for track collection, not quad.

4. Dolby surround does solve the side and back imaging problem. I have been able to smoothly pan a sound all the way around the room with no sudden jumps or vague localizations.

Left back to right back is the most noticeable if you place your back speakers to the side.

 

[jaybird100]

Left back to right back is the most noticeable if you place your back speakers to the side.

The ability of your matrix decoder has much to do with your result. I've been through a number of different decoders in my time, from EV-4 to the Involve Surround Master v2. While all matrix systems are a compromise, the decoder makes, or breaks, the listening experience; minimizing the effect of that compromise. The Surround Master does the best job of any decoder I've heard, and will make stereo recordings come to life, often delivering an enveloping sound field as convincing as a matrix quad recording. Had this technology been available in quad's heyday, it might have gone dormant, as it did.

 

[Q-Eight]

Left back to right back is the most noticeable if you place your back speakers to the side.

It also depends very much on what is being sent to the back corners. Generally speaking, humans will detect bright sounds first. When I mix to four channel, I place percussives in the back corners where possible. That way if you've got a tambourine in BL and a Cowbell in BR.... a person can really hear it. I generally reserve my rear channels for percussives, backing vocals, guitars, electric keyboards and echo. Some instruments will get lost if you mix them to the back with other instruments. An example: Darker sounds, or bass.... it will get lost often drift to back center. It's just the way we hear certain things.

 

[furui_suterioo]

Is this some sort of a tone generator for discrete quad FM alignment?
RARE! Fisher CD4 4 Channel Stereo FM Alignment Generator ONE OF A KIND Fisher! | eBay

 

[Soundfield]

Is this some sort of a tone generator for discrete quad FM alignment?
RARE! Fisher CD4 4 Channel Stereo FM Alignment Generator ONE OF A KIND Fisher! | eBay

Nope, nothing to do with broadcasting. It was a standard bit of test equipment for aligning the FM elements of retail CD-4 demodulators. It was specifically called up in the test equipment lists of Fisher service manuals of course. Here it is specified in the manual for the Fisher 4035 receiver for example: