• QuadraphonicQuad welcomes you and encourages your participation! Treat all members with respect. Please keep all discussions civil, even when you have a strong opinion on a particular topic.

    Do not offer for free, offer for sale, offer for trade, or request copies or files of copyrighted material - no matter how rare or unavailable to the public they might be. We do not condone the illegal sharing of music. There are many places on the internet where you can participate in such transactions, but QuadraphonicQuad is not one of them. We are here to encourage and support new multichannel releases from those companies that still provide them and as such the distribution of illegal copies of recordings is counter-productive to that effort. Any posts of this sort will be deleted without notification.

    Please try to avoid discussions that pit one format against another. Hint for new users: make liberal use of the search facilities here at QuadraphonicQuad. Our message base is an incredibly rich resource of detailed information on virtually all topics pertaining to surround-sound. You will be surprised at what you can find with a little digging!

MidiMagic's "Quadraphonics and Surround Index Page"

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humprof

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Anyone know anything about the creator of this site, Larry Robinson? (Maybe he's a QQ member?) Someone on the Quad Traders FB group posted a link to one of the subpages, "Quadraphonic Systems," which explains, in detailed and technical--but also clear and comprehensible--language how all the legacy surround methods work. Brilliant stuff, at least to an impressionable non-expert like me. Totally, geekily, OCD-level meticulous, replete with charts, graphs, and diagrams. But maybe the engineers here can confirm whether it's good information.

 

Circular Vibes

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@MidiMagic is a member here and as far as I can tell, he is well respected and considered knowledgeable. I will admit that I do not understand the math involved but do seem to make some sense of his diagrams. His webpages are bookmarked on the homepage of QQ. I do love his pages on record changers. That is an area that I can comment more ably. I find a few things I might disgaree with but the most of that area I do agree and like his views. I do wish he would drop by QQ more often.
 

The Auroran

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Sorry to add a slightly negative post, but that "MidiMagic" site must be read with a deal of care. There's quite a bit of false information there.

I know it looks all colorful and flashy but the deeper you dig the more bad news you uncover.
 

Circular Vibes

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Sorry to add a slightly negative post, but that "MidiMagic" site must be read with a deal of care. There's quite a bit of false information there.

I know it looks all colorful and flashy but the deeper you dig the more bad news you uncover.
Can you elaborate please? Maybe an example of false information or two? I might have disagreed on a couple minor points on his record changer comments but I don't know the math involved well enough to comment on the 4 channel info. I would have liked to see some actual facts in your post rather than just saying there is "quite a bit of false information ".
 

Circular Vibes

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I do disagree with #1. As to #4, I have yet to find a CD4 disc that the carriers were in fact too worn off to use. If it were that worn, I'd likely not play it in stereo for all the background noise. I do agree with using a CD4 pickup or at least one of the newer Micro Line cartridges. I wouldn't have refered to that as "quite a bit of false information" though.
 

humprof

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I do disagree with #1. As to #4, I have yet to find a CD4 disc that the carriers were in fact too worn off to use. If it were that worn, I'd likely not play it in stereo for all the background noise. I do agree with using a CD4 pickup or at least one of the newer Micro Line cartridges. I wouldn't have refered to that as "quite a bit of false information" though.
First: welcome to QQ, @The Auroran! Without hurting anyone's feelings or inviting the sort of ego-tripping pissing matches that often erupt on other hobbyist discussion boards (but generally not here), I'd be curious to hear more, too. What @sjcorne quoted above just seems like crotchety snark--and I don't mind that at all. (I get it: for many people CD-4 may be more trouble than it's worth. Run away!) I don't also mind it if somebody has a strong opinion about a matter that's often disputed--as long as they acknowledge the controversy. But if something is just dead wrong, or has no credence from the vast majority of experts in the field, then I wanna know about it...
 

Circular Vibes

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I certainly didn't want a flame war either. There was enough of that long ago and isn't worth dredging up. I just want to know where MidiMagic may have differing info. I meant nothing more than discussion on what sjcorne posted or The Auroran posted as possible misinformation. If anything more than that is implied, then I apologise. I certainly had my share of Guinness induced CD4 problems and problem solving. It ain't for the faint of heart but it ain't insurmountable either. I suspect the issue may be the math of different matrices but I can not speak knowledgeably to that. I am just glad when vintage quad works. I am also glad to see another Quaddie in our midst and hope for much more open discussion. QQ has become more dirgital oriented and I have felt a bit out of place. If I got $20 bux in my pocket and can buy a quad LP,reel, 8 track or a digital surround disc/set, I likely will buy the analogue stuff. There are some dirgital titles out there that will make a liar outta me though!
 

The Auroran

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Can you elaborate please? Maybe an example of false information or two? I might have disagreed on a couple minor points on his record changer comments but I don't know the math involved well enough to comment on the 4 channel info. I would have liked to see some actual facts in your post rather than just saying there is "quite a bit of false information ".
It's been a little while since I've been there, because I found it of no use, and I'll pick a couple at random and will post as a reply to this posting

Auroran
 

The Auroran

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I certainly didn't want a flame war either. There was enough of that long ago and isn't worth dredging up. I just want to know where MidiMagic may have differing info. I meant nothing more than discussion on what sjcorne posted or The Auroran posted as possible misinformation. If anything more than that is implied, then I apologise. I certainly had my share of Guinness induced CD4 problems and problem solving. It ain't for the faint of heart but it ain't insurmountable either. I suspect the issue may be the math of different matrices but I can not speak knowledgeably to that. I am just glad when vintage quad works. I am also glad to see another Quaddie in our midst and hope for much more open discussion. QQ has become more dirgital oriented and I have felt a bit out of place. If I got $20 bux in my pocket and can buy a quad LP,reel, 8 track or a digital surround disc/set, I likely will buy the analogue stuff. There are some dirgital titles out there that will make a liar outta me though!
Have little time with the modern digital formats, push them and they go. Far more fun can be got from the original analogue systems because it was very much about taking the first steps into a new world, with all the problems that could be imagined thrown in for free.

What flame war? And CD-4 is it's own nightmare, enough to even scare Freddie off, those who venture into that world and succeed in getting it to work are truly masters of that art.
 

Circular Vibes

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What flame war? And CD-4 is it's own nightmare, enough to even scare Freddie off, those who venture into that world and succeed in getting it to work are truly masters of that art.
The flame war was a few years ago and my eyes are still ringing. I won't say more than there were people with much more knowledge than I duking it out over matrix decoding. I still highly respect all parties but wish common quad ground could have been found. As to CD4, I have a shelving unit of demogitators (tm QL) and carts and tables from trying to make it work. It does now and my wallet is still seeking quad buying therapy! Hope you didn't think I was trying to call you out or anything, I genuinely still have plenty to learn and will listen to your experience too.😆
 

The Auroran

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Can you elaborate please? Maybe an example of false information or two? I might have disagreed on a couple minor points on his record changer comments but I don't know the math involved well enough to comment on the 4 channel info. I would have liked to see some actual facts in your post rather than just saying there is "quite a bit of false information ".
Sorry for the delay in doing this, time of year etc.

As i said, the Midimagic site is of very dubious use for anyone looking to learn about the quadraphonic systems of the 1970's. The worst thing about it, and this is obviously a deliberate move to make any of the equations of no worth, because they have been truncated and then rounded up. 😫

This is not acceptable in the scientific or mathematical circles and can only be done to restrict others from working on the matrixes.

The decode equation for QS is wrong, period. As is the equation for BMX, this matrix comes under the same "RM umbrella" as QM, QS, and QX, therefore follows specific rules as laid down by the Japanese Record Industry.

What is purported to be BMX is "fake news" (copyright:Trump)
I could write a book on the wrong, fake and useless information on that site but I'll just leave it to you, the reader, to decide for yourself.
 
Last edited:

MidiMagic

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I am here (MidiMagic).

The information is as accurate as I could obtain, excepting that I did not use the trig versions. I put the trig info in another article How to do Calculations for Quadraphonics on the site. The rounded (not truncated) values are for setting matrix parameters on analog controls (such as the mixer I use and my surround controller). The average user does not have a scientific calculator at hand.

The "QS" equations on the site (as of yesterday) are the Scheiber equations. I put QS into the same position in the chart as the Scheiber equations because the encoding positions are the same and the same decoders work. The article was originally from the operation manual for my SSC-10 surround control unit. It treats Scheiber and QS identically. I was going to add the QS equations to the web page and forgot I hadn't done it. I will do it as soon as possible.

The BMX equations are derived from the equations in "Discrete-Matrix Multichannel Stereo" D.H. Cooper & T. Shiga, Journal of the Audio Engineering Society 06/1972 V 20 pp. 346-360. The article does not directly give 4-corners coefficients. If you have different BMX equations, I would like to see them.

BMX is not QS. It is the baseband of UD-4. But Denon also had an early system called QM with regular-matrix properties. Don't confuse them. QS decoders play a faux version of BMX because sounds in BMX in between mics comes out at the QS and RM front.

My info about UMX, BMX, and UD-4 are from "A Geometric Model for Two Channel Four Speaker Matrix Stereo Systems" Michael Gerzon, Journal of the Audio Engineering Society 03/1975 V 23 pp. 98-106. Notice how BMX and UMX are recorded at right angles to QS in Gerzon's diagrams.

My CD-4 writings come from experience. I have NEVER heard a CD-4 recording that worked properly. But at the time I had CD-4 equipment (that was given to me by my employer as an evaluation sample), I was a college student and bought used records. I was using a PE 2038 with low capacity cables, an AT-12 cartridge, and a JVC demodulator. But I never heard a demonstration of CD-4 that worked right either. I always heard at least one of these:

1. The loud snapping from dust on the record
2. The demodulator kicking in and out (probably improper cartridge installation)
3. The background hiss from having played the same record over and over

I decided early on that CD-4 was not worth the effort.

Your mention of Trump is irrelevant.
 

MidiMagic

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Actually, those were the QS equations (not Scheiber), except that they were normalized to produce a unity resultant (as all of my coefficients are). With the normalized coefficients, all linear resultant vectors have the length 1.

Sansui published the following decode equations:
lf = 1.0L + .414R
rf = .414L + .1.0R
lb = -.1.0Lj + .414Rj
rb = -.414Lj + .1.0Rj

The normalized Sansui equations:
lf = .92L + .38R
rf = .38L + .92R
lb = -.92Lj + .38Rj
rb = -.38Lj + .92Rj

Notice that the second set is the first set multiplied by .92 - Sansui had just turned the volume up by 1.08 (and the original EV equations were not normalized and turned up the back channels more than the front).
 

gene_stl

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The Auroran was banned because of being a troll. A review of his three pages of posts shows that HE knows everything and all of the rest of us know nothing.
It is a shame that we no longer have the benefit of his superior knowledge. Then again we aren't really worthy of it.

I find MidiMagic's web pages , useful and informative. In another life (gemology) I have had exposure to the Poincare' sphere.
 
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