Lou Dorren: A new CD-4 Demodulator!!! [ARCHIVE]

QuadraphonicQuad

Help Support QuadraphonicQuad:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Sorry, I didn't mean it to sound that way and thank you for your knowledge. I respect your opinion. Any input by anyone is most welcome.

I'm just intrigued to have Lou possibly answer these 2 questions with his engineering background and knowledge of Quad and that is only what I meant.
 
Last edited:
The point of bringing up SQ in this thread is that's where Lou is. Of course, You could ask him to go over to the SQ thread, but it's hardly worth the trouble for one question. But one becomes two, two becomes three. So I will put in my two cent's worth. In spite of my big talk about having 5 ears and a big ol' bass ear, I really have only two ears. No, really, I'm not kidding. Yet I can tell direction of sounds in all directions, and so can all of you. If it was otherwise, you wouldn't like quad. The point is that our brains CAN sort it all out, with only two channels. So, this suggests that it could be possible to make a matrix decoder discretely separate the quad sounds, we just haven't developed the technology sufficient to do it yet. Also, it might be possible to wrap a stereo panarama around the room and have actual separation between the front speakers. Once again, this will require a technology yet developed. But as far as I can see, there is no will, so it probably will not happen within my lifetime. The future of multichannel is probably Blue Ray if anything. It seems to be winning the format war. Whether we will see any studio surround recordings in Blue Ray remains to be seen. But it will be possible, because the technology and infrastructure will be in place.

The Quadfather
 
Hello Quadranarians,

Sorry I have not been here the last few days. I managed to get a terrific dose of the Rhino Virus. I, however, feeling better, think it is time for the "SOAP BOX".

Old Quad Guy, The information theorem is one of my favorite discussion subjects. It states that for a given number of input channels, there must be the same number of transmission channels, to reproduce to the same of output channels. This is then defined by 3 numbers. Take Discrete Quad for example. It is defined as 4-4-4, 4 input channels, 4 transmission channels, 4 output channels. It fulfills the Information Theorem perfectly. Now what about any of the matrix systems. These systems have 4 input channels, 2 transmission channels, and four output channels. They fail the Information
Theorem even with all the processors. This is because the 4-2-4 systems are all 2 channel stereo with 4 inputs and 4 speakers.

Here is an analog that should demonstrate what a matrix 4-2-4 system does. Imagine four soda glasses, each one half filled with a different soda. Glass 1 has orange soda, glass 2 has root beer, glass 3 has cherry soda and glass 4 has lemon soda. These are the 4 input channels with the color of the soda equivalent to the phase shift. Now imagine 2 empty glasses representing the 2 transmission channels. Now take input glass1 and input glass2 and empty the contents into transmission channel glass 1. Then take input glass3 and input glass4 and empty these contents into transmission channel glass 2.

Now here is the problem, having poured the orange and the root beer into the same glass, regardless of color, how do you separate them back into their original discrete soda form? The answer is you can not!! All the 4-2-4 matrix systems do is to mix (add) 2 signals on the left together and put them on the left channel and they do the same for the right channel. Phase shifting at audio frequencies serves no purpose unless you are using it as a "guitar effect".

Wait a minute, what about , Tate, Prologic etc.? Well these devices have an interesting effect. When the Information Theorem is satisfied, they can do something that appears to be correct. When the Information Theorem is not satisfied, they become quite confused. There are 2 conditions in matrix 4-2-4 where the Information theorem is satisfied. Condition number 1 is sending only 1 of the 4 channel at a time. The example is LF only with LB,RF,RB silent. In this case the Tate, Prologic,etc processors have enough information to turn the level down on LB,RF,RB and leave the level up on LF. If only one channel is sent at a time, the sound can be made to appear going around the room. Quadraphonic right? No, it is only a special effect! The minute there are more then 2 audio channels being sent, all bets are off. By the way, when all 4 channels are input on a 4-2-4 matrix system, there will be at least 1 pair of channels on the output that will have no more than 3dB of separation.

I know there are a lot of you out there with large libraries of SQ and QS records. I also know that some of these synthesized Quad records can sound interesting. I recommend that you enjoy them, but remember they are synthesized and not true Quad as is discrete Quad.

The answer to your Questions Old Quad Guy, no it will never be possible to decode 100% of a QS or SQ recording because there really was nothing encoded! Contrary to popular opinion, the Tate unit was not very complex and could be easily duplicated.

Quadfather, Good thoughts, and remember TAAS.

Lou Dorren
 
Last edited:
Regarding CD-4 and Playback Turntable
RPM Accuracy:

Proper operation of CD-4 is predicated on
CD-4 discs being played back at exactly
the intended RPM.

How much of an RPM variation will the CD-4
system tolerate?

Kirk Bayne
 
Ah the Edgar Winter Group - they do only come out rarely now.
Now I see why QS and SQ matrix did seem to work - only when the other channels were quiet.

Got a quote on a shibate stylus 4MD10X $A229 and a 4 MD30x eliptical $A99.95 retail - so those stylus are getting expensive or its just a rip off - a total of $A330. But, from another retailer $A75 and $A55 - much better, I think.

Hope Lou has a final solution for the demodulator problem - disks will last well but a demod'r won't.

Cheers
 
Hello Quad Fans,

kfbkfb, A +-5% variance is still usable. Direct drive and servo turntables are the best.

bad robot, You and everyone will be quite happy with the new CD-4 cartridge with Shibata stylus, both price and performance!

NEWS FLASH: Blu Ray wins High Definition War!! Toshiba to stop manufacture HDDVD today!

Lou Dorren
 
Last edited:
Hello Qyad Fans,

kfbkfb, A +-5% variance is still usable. Direct drive and servo turntables are the best.

bad robot, You and everyone will be quite happy with the new CD-4 cartridge with Shibata stylus, both price and performance!

NEWS FLASH: Blu Ray wins High Definition War!! Toshiba to stop manufacture HDDVD today!

Lou Dorren
Lou, perhaps good news for music fans, but i wonder if we just gave the keys to exxon and shut down the rest of the stations. Sony has fought tooth and nail to own every format(yep, you and i know that is where the big $ is) and it now wants to control everything from production thru distibution. This company is not gonna make it inexpensive to release material. It just seems to make it more difficult to see much material being released in real multichannel form for music only. If it was some other company else..... optimisim might win. I wonder if even a progressive place like Telarc will even make that jump.
 
Hello Quad Supporters.

Quadtrade,
Ted, The Sony Blu Ray is far superior over the Toshiba HDDVD. The most important criteria is storage capacity. Blu Ray is capable of multi layer storage eventually beyond 500 GB. HDDVD was limited to 25 GB. This means that some day we may actually get real High Definition Television without throw away digital data compression!

Old Quad Guy, Is that you behind the mixing console? What studio?

Lou Dorren
 
Old Quad Guy, Is that you behind the mixing console? What studio?

Hello Lou,

No, it is not me...yet! Although I’m getting there bit by bit. I picked this as my avatar with much respect for the engineer in the photo (who I wished I knew more about), and that I will someday be lucky to live long enough to contribute something positive with music and Quadraphonic preservation. It is a photo of Grammy Award winning sound engineer Carson Taylor at an actual Quadraphonic recording/mixing station working on a Quad track at Capitol Records' Hollywood studios in 1974. The full photo shows a speaker behind him. It comes from the back of a Capitol Quad sampler “Magnavox Presents a Sound Experience.”

Old Quad Guy
 
Regarding CD-4 and Playback Turntable
RPM Accuracy:

Proper operation of CD-4 is predicated on
CD-4 discs being played back at exactly
the intended RPM.

How much of an RPM variation will the CD-4
system tolerate?

Kirk Bayne

The tolerance of the CD-4 demodulator is probably the LEAST of your worries. While not everyone has perfect ABSOLUTE pitch (some do, like Lou), most everyone has very good relative "perfect" pitch. It is well known that when silent movies were made, the speed of the "recording" often varied from camera operator to camera operator. When they went to sound recording synchronized with the action on the film, they needed to standardize on the frame rate (24fps) to make everything work correctly. If you have an adjustable speed turntable, try to play something and alter the speed. You will notice it VERY quickly, and it doesn't take much. It turns out that your ears are better pickups than your eyes. We humans can tolerate quite a bit of distortion in the picture, but very little in the sound. This is one of the reasons that video is more compressed (ratio wise) than the sound in MPEG style recordings.
Of course, the best is no compression at all, hopefully BluRay will assist in that someday.
 
Regarding the QSI5022:

Have the new DSP based LPFs and BPFs
been tried with the QSI5022?

If so, how much better is the CD-4
sound qualiy?

Kirk Bayne
 
Hello Quad People,

kfbkfb,
Kirk, I have no way to really try that. The QSI5022 has different input-output impedances and also expects passive filters with no gain. The new filters have been optimized for the new design. Although it would be possible to bread board these filters into an old demodulator, no useful information for the new demodulator would be obtained. I have no doubt, however, that the QSI5022 performance would be improved.

Lou Dorren
 
I said all I will say about politics in this thread. True, this isn't the place. So, how many of you have figured out the humorous aspect of Lou's papers?
I did.

The Quadfather

I'm pretty sure I did too but will wait until Lou discloses it to see if I'm correct.:D

All I can say is after reading the first four installments, I am in AWE! :worthy

Doug
 
Regarding Speaker Polar Response:

What's the acceptable speaker polar response
(range) for good Quadraphonic imaging (using
the speakers set up in a square arrangement)?

Kirk Bayne
 
Regarding Speaker Polar Response:

What's the acceptable speaker polar response
(range) for good Quadraphonic imaging (using
the speakers set up in a square arrangement)?

Kirk Bayne
Directionally, for getting good localization of the rear sounds you need a fairly dampened room, especially if the rear speakers are almost side speakers as favored by 5.1. Speakers with a restricted polar response could help but if the effect may be too subtle to be noticeable, particularly in a live room.

A square arrangement may not be optimal for enjoyment but perhaps great for dissecting mixes.
 
Hello Quadafiers,

kfbkfb, proufo,

Kirk and Pablo,

A small soap box this time. Best speaker location and pattern were part of the Acoustic double blind study that we conducted at the NQRC (National Quadraphonic Radio Committee). The ideal polar pattern for accurate 2 dimensional Quadraphonic sound reproduction is Cardioid synchronized wavefront generation. This is defined as a full range speaker using a woofer, a midrange, and a tweeter mounted so that the generated wavefront from each transducer starts from the same aligned origin. As I indicated in a previous post, the speakers are placed in a square configuration with each at a 45 degree angle pointed at the diagonal speaker. The key is symmetry. This yields a nice, well defined listening area. Symmetrical X and Y vectors display fairly wide preferred positions and excellent phantom image display.

5.1 systems, being non-symmetrical have a distorted Y vector which damages the 2 dimensional reproduction. Room acoustics should be adjusted to control audio standing waves.

Lou Dorren

PS Three of you have found the humor so far!
 
Hello Lou, that there are since a few days no more asks may be also a good thing. So you find more time to finish the part V of your technical instructions for us curious fans.
But you may nevertheless answer one ask from me: Will the new (your) demodulator have like the high praised SH-400 for the adjustement also a VU /level meter? OK, we can of course also adjust the channel separation like the usual mode, but I and others have an interess to know such details, before we have finally the demodulator in the hands.

Dietrich
 
Lou,
I assume you have some prototype demodulators on the test bench. I would love to see your "work in progress" and any test results that are available. The theoretical articles are really whetting my appetite and a couple of photographs would be great.

Malcolm
 
Back
Top