"Synthesizer" mode for the Surround Master?

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jsrstereo

Senior Member
Since 2002/2003
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Jan 22, 2003
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Tucson, formerly Oklahoma City
We all know that the Sansui VarioMatrix decoders include a "Synthesizer" mode for stereo sources along with "QS" decoding. What's the chance of future SM units also including a Synthesizer mode? Desirable or not?

For me (a certifiable non-techie), this raises the question: just how do these two modes differ in operation from each other?
 
We all know that the Sansui VarioMatrix decoders include a "Synthesizer" mode for stereo sources along with "QS" decoding. What's the chance of future SM units also including a Synthesizer mode? Desirable or not?

For me (a certifiable non-techie), this raises the question: just how do these two modes differ in operation from each other?

You've touched on a subject near & dear to me. This question of a synthesizer mode to Chucky has been brought up before. Basically he feels "there's enough psycho-acoustic goodness baked into the Surround Master that it doesn't need it." And that it would just add to consumer confusion if offered. My own opinion is that the synth mode brings a lot of value added choice to decoding & it's less confusing, more useful than the TSS mode.

Anyways, whether it's Sansui Variomatrix or the Involve implementation they both decide where a sound is located the same way. Any direction L/R is determined by the amplitude level difference between the input chs. Whether it is in the front half or rear is determined by phase difference between the chs. In phase it is in front, opposite phase it is in rear. Where there is a left only (right only) input there's zero phase difference but large level difference. So that would be decoded as center left (center right).

In the Sansui synth mode the 2 input chs are mixed opposite phase at ~-7dB level. That is the left ch is polarity inverted and mixed into the right input ch 7 dB lower. Same thing for right mixed into left.

In practical terms this means a bass guitar panned hard left to right in the Involve QS decode will start center left, move to center front, and continue to center right.

In a Sansui synth mode that bass guitar would start in left back, move to center left, then left front, center front, right front, center right, & end up in right back.

Under those conditions it can be said that the Involve offers 180 deg decoding while with synth you have 270 deg decoding. The latter really opens up the soundfield. Of course there can be any combination of phase/amplitude combinations on a stereo recording & the Involve will pick up on this & if it meets the requirements certainly you get independent sounds popping up in the rear .s.

If/until the option is integral to the Surround Master there is no easy non-techie way to do this. There is no available outboard box to add on either. I have posted multiple times about the value of pre-synth encoding & if you care I'll link to them.
 
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I brought the synthesizer mode to Chucky a long time ago when they were starting
But as you said he was not very interested in it
I used to use it a lot on Stereo
But a number of times i had to lower the rear channels as the level was too high
It was easy for me to do but I slowly went back to QS for decoding stereo
 
But a number of times i had to lower the rear channels as the level was too high
It was easy for me to do but I slowly went back to QS for decoding stereo
Yes that seems exactly correct. If the synth mode moves more direct sounds into the rear, then it will be louder than before. Drop the rear chs a bit & all falls into place.

The Sansui Hall mode put undecoded stereo in the front chs & mixed in phase blending into the rear chs. This made for sometimes a front balanced soundfield ideal for concerts & such. I would push the level up a few dB in the rear & again it melded into a very nice soundfield.
 
I brought the synthesizer mode to Chucky a long time ago when they were starting
But as you said he was not very interested in it
I used to use it a lot on Stereo
But a number of times i had to lower the rear channels as the level was too high
It was easy for me to do but I slowly went back to QS for decoding stereo
Sansui should not of called it synthesized, it doesn't synthesize anything it just extracts whatever is in the mix by stretching it over more speakers. It's the only way to listen to stereo!
 
"If/until the option is integral to the Surround Master there is no easy non-techie way to do this. There is no available outboard box to add on either. I have posted multiple times about the value of pre-synth encoding & if you care I'll link to them." - Sonic Wiz

Please do post the link.

Thanks, John R
 
Sansui should not of called it synthesized, it doesn't synthesize anything it just extracts whatever is in the mix by stretching it over more speakers. It's the only way to listen to stereo!

Is this method (Sansui's Synthesizer) of wrapping the mix 270 degs around the sound field similar to Penteo's "Panorama Slicing"?
 
"If/until the option is integral to the Surround Master there is no easy non-techie way to do this. There is no available outboard box to add on either. I have posted multiple times about the value of pre-synth encoding & if you care I'll link to them." - Sonic Wiz

Please do post the link.

Thanks, John R

The most detailed post I've made on doing the synthesis mode on a PC is here.

Sometime back I moved to a real time hardware solution & details on my DIY project is here.

The harware set up is now what I use almost exclusively. However there are still benefits & more control doing it on a PC. And someone is more likely to do it that way than pick up a soldering gun like I did.
 
Sansui should not of called it synthesized, it doesn't synthesize anything it just extracts whatever is in the mix by stretching it over more speakers. It's the only way to listen to stereo!
Haha well of the many things we agree on I will beg to differ on that 1st sentence. I'd say that the basic QS/Involve decoding is honestly the purist approach. It doesn't add anything just decodes the audio according QS coefficients. The synth mode definetly strays from that because it is what it is: added out of phase bleneding between the input chs.

I'd say Sansui should have just had a stereo decode mode that included a +- phase balance pot along with the usual L/R level balance. You could adjust freely adjust forward or rear phase blending to suit the material. When it sounds right, it is right!
 
Haha well of the many things we agree on I will beg to differ on that 1st sentence. I'd say that the basic QS/Involve decoding is honestly the purist approach. It doesn't add anything just decodes the audio according QS coefficients. The synth mode definetly strays from that because it is what it is: added out of phase bleneding between the input chs.
I would still have to disagree about the QS/Involve approach being more pure. Using that approach a hard panned left signal appears equally from both left side speakers and a the same from the right. QS Surround on the other hand places the hard panned signal to the respective back speaker only. I would call that a more pure approach. The only real negative of in phase and out of phase blending of the stereo signals is a slight reduction in the level of a centre front or centre rear signal. Circle Surround music mode operates similarly to QS and would likely benefit from pre-synth as well. I'll post more on that topic as I do more listening experiments with CS decoding. I do find Circle surround to sound more active than QS or Involve but QS is more natural; apparently CS uses gain riding logic (similar to old SQ) but dual or more bands to minimize pumping effects, I think that vario-matrix decoding is better.
 
Umm err dunno
Its really against our philosophy but if we get a free moment it really is not very hard to program it as an optional mode (say in replacement to TSS ). Issues are more to do with my other post later tonight re whats happening. But yeah - could do it for Rustyandi as a sample for and see where it goes..
 
Haha well of the many things we agree on I will beg to differ on that 1st sentence. I'd say that the basic QS/Involve decoding is honestly the purist approach. It doesn't add anything just decodes the audio according QS coefficients. The synth mode definetly strays from that because it is what it is: added out of phase bleneding between the input chs.

I'd say Sansui should have just had a stereo decode mode that included a +- phase balance pot along with the usual L/R level balance. You could adjust freely adjust forward or rear phase blending to suit the material. When it sounds right, it is right!

I have built exactly that, except that the front pair gets adjustable + blend and back channels get adjustable - blend. I use it to recover hall ambiance from classical records.
 
Umm err dunno
Its really against our philosophy but if we get a free moment it really is not very hard to program it as an optional mode (say in replacement to TSS ). Issues are more to do with my other post later tonight re whats happening. But yeah - could do it for Rustyandi as a sample for and see where it goes..

IIRC you had extensive seperation measuments posted at one time comparing the Surround Master to a QSD-1. Again IIRC that QSD-1 was defective & you couldn't compare stats for all channels. That makes me wonder if you have ever properly heard the synth mode on a Sansui product?
It was ultra-simple for Sansui to do this in analog mode but it might be more involved (no pun intended) to do it on the SM. However it is easy simple quick to do on a PC. Just use a channel mixer to create the out of phase blending. Technically this should be at -7dB but the few Sansui units I actually measured had the blend closer to -10dB. They probably figured there was already x amount of rear ch information on a record mix so too much synth blend would certainly be worse than too little.

Just today in my bathroom library I was reading an article from April '74 Pop Electronics reviewing a Sansui QRX-3500 receiver. The concluding paragraph read:
"We most appreciated the QS Synthesizer that gave better "4 ch sound" from 2 ch programs than we have gotten from 4-ch records played through ordinary matrix decoders. Any matrix decoder can create an abient enhancement from 2 ch records but that is lacking in solid directionality. In contrast the Variomatrix Synthesizer mode creatwes 4 distinctly different chs from 2 and does it most of the time that doesn't sound awkward or artificial."

With all the other craziness you posted elsewhere happening I'm sure this isn't at the top of your to do list. But when you get a chance I suggest taking PF's Money in stereo & play it through the SM with/with out the phase blend. I had the stereo LP & Played it through the Sansui synth mode many times before I had the SQ LP. I was relived that my new SQ purchase sounded almost as good played through SQ full logic as the stereo through QS synth!
 
IIRC you had extensive seperation measuments posted at one time comparing the Surround Master to a QSD-1. Again IIRC that QSD-1 was defective & you couldn't compare stats for all channels. That makes me wonder if you have ever properly heard the synth mode on a Sansui product?
It was ultra-simple for Sansui to do this in analog mode but it might be more involved (no pun intended) to do it on the SM. However it is easy simple quick to do on a PC. Just use a channel mixer to create the out of phase blending. Technically this should be at -7dB but the few Sansui units I actually measured had the blend closer to -10dB. They probably figured there was already x amount of rear ch information on a record mix so too much synth blend would certainly be worse than too little.

Just today in my bathroom library I was reading an article from April '74 Pop Electronics reviewing a Sansui QRX-3500 receiver. The concluding paragraph read:
"We most appreciated the QS Synthesizer that gave better "4 ch sound" from 2 ch programs than we have gotten from 4-ch records played through ordinary matrix decoders. Any matrix decoder can create an abient enhancement from 2 ch records but that is lacking in solid directionality. In contrast the Variomatrix Synthesizer mode creatwes 4 distinctly different chs from 2 and does it most of the time that doesn't sound awkward or artificial."

With all the other craziness you posted elsewhere happening I'm sure this isn't at the top of your to do list. But when you get a chance I suggest taking PF's Money in stereo & play it through the SM with/with out the phase blend. I had the stereo LP & Played it through the Sansui synth mode many times before I had the SQ LP. I was relived that my new SQ purchase sounded almost as good played through SQ full logic as the stereo through QS synth!


Whats/ Whos IIRC???
 
Whats/ Whos IIRC???
????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????........................
 
????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????........................
If I Remember Correctly - A constant challenge for us old farts! o_O
 
IIRC= If I Recall Correctly

And I did. Post 136 on page 7 shows tests done on the QSD-1 compared to the SM. there it was said

During the testing it was discovered that both the right output channels of the Sansui QSD-1 decoder unit were faulty so only the left channels could be used in the testing and comparison of the two decoder units. It is highly unlikely that the fault in the right channels would affect the performance of the left channels in any way which would not be immediately noticeable in the tests.

I agree it didn't invalidate the testing so much as I was trying to say you may not have ever heard the classic Sansui Synthesizer mode because of this. I dunno... maybe you've got loads of Sansui quad gear laying around & know exactly what the synth mode sounds like. Maybe you don't. It's worth a listen
 
IIRC= If I Recall Correctly

And I did. Post 136 on page 7 shows tests done on the QSD-1 compared to the SM. there it was said



I agree it didn't invalidate the testing so much as I was trying to say you may not have ever heard the classic Sansui Synthesizer mode because of this. I dunno... maybe you've got loads of Sansui quad gear laying around & know exactly what the synth mode sounds like. Maybe you don't. It's worth a listen
See, what'd I tell ya!
 
I used to enjoy the synthesizer mode on my Audionics Space and Image Composer. Then it started malfunctioning. So, I started playing the stereo records in the SQ mode. I got to where I liked the SQ mode better than the stereo enhance mode. The stereo enhance mode had started working again later. So when I get my Involve decoder, I will try the stereo records in SQ and QS mode and see which I like better. I could see that it might even depend on the material being presented to the decoder. We will see how it does.
 
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