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Question About the Front Channels in the SM...and others

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Wagonmaster_91

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I may have asked this question before in a general sense, but since we have someone who actually works for a manufacturer on the QQ I figure I might get a better informed answer. The question is: In surround synthesizer mode(s) (or when a stereo signal is run through the SM and it creates additional channels), does it alter in anyway the original front left and right channels?

I ask this because I use separate amps for my front, rear and surround channels. For that reason, I don't run the front L&R feeds from a decoder back to the front channels amp since that amp is already receiving the front L&R signal from the original source. I figure the fewer devices a signal has to run through, the less chance of signal loss, colorization, distortion, etc. Plus, I like being able to control volume and tone for each pair of channels because as we all know surround mixes can vary widely in their balance of front to rear to surround to height/overhead.

OK, so for those of you who have deep knowledge of the legacy decoders - Tate, Sansui QSDs, AS&IC, Lafayette L or W, EVX-44, Sonys, Fosgates, etc: Do any of those change, add or subtract anything from the front channels when processing a stereo signal to "fake surround" ?

I don't think so. Correct?
 

chucky3042

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Hi Wagonmaster_91

Yes we and most good stereo to surround processors do change the front left and right outputs. In our case we actually remove any rear content from the front signals so if you just wired the fronts direct from the source the net result is a reduced front to rear separation and a reduced surround image. Early simple surround techniques such as the old Halfer Dynaco left the fronts alone and subtracted L-R for the rear content.

I also note for those who insist on the silly center channel that we also remove any center content from the left and right channels and stick it in the wretched center (stupidly under the TV!)

Regards

Chucky
 

Sonik Wiz

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I may have asked this question before in a general sense, but since we have someone who actually works for a manufacturer on the QQ I figure I might get a better informed answer. The question is: In surround synthesizer mode(s) (or when a stereo signal is run through the SM and it creates additional channels), does it alter in anyway the original front left and right channels?

I ask this because I use separate amps for my front, rear and surround channels. For that reason, I don't run the front L&R feeds from a decoder back to the front channels amp since that amp is already receiving the front L&R signal from the original source. I figure the fewer devices a signal has to run through, the less chance of signal loss, colorization, distortion, etc. Plus, I like being able to control volume and tone for each pair of channels because as we all know surround mixes can vary widely in their balance of front to rear to surround to height/overhead.

OK, so for those of you who have deep knowledge of the legacy decoders - Tate, Sansui QSDs, AS&IC, Lafayette L or W, EVX-44, Sonys, Fosgates, etc: Do any of those change, add or subtract anything from the front channels when processing a stereo signal to "fake surround" ?

I don't think so. Correct?
Well, firstly the Surround Master does not have a dedicated synthesizer mode in the classic sense. When you set it to Involve 4.1 for example it functions as a QS decoder. Your set up as described is very close to Sansui's Hall mode where 2 ch material, stereo or quad, was sent un-decoded to the front speakers & the only decoded content was sent to the rears. I found this useful for some classical recordings or ssome live rock redcordings that were marginally done.

Your set up as described will not decode QS/SQ correctly or fully benefit stereo enhancement on the SM. You would probably do as well to use an old timey EV decoder.

Yes, the Sansui's, Fosgate, etc all modify the front chs in different ways to achieve the manufacturers desired goals.
 
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Wagonmaster_91

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Thanks for the info, Chucky. Actually, my system is wired both ways - I can listen to all channels through a decoder OR the way I described in my post.

The Dynaco method was my first experience with 'surround' sound way back in late 60's. That's where my journey started oh so many years ago.
 

Soundfield

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In our case we actually remove any rear content from the front signals so if you just wired the fronts direct from the source the net result is a reduced front to rear separation and a reduced surround image. Early simple surround techniques such as the old Halfer Dynaco left the fronts alone and subtracted L-R for the rear content.
I wondered if I should remove the rear channel signal from the fronts in the latest version of my line level Hafler Decoder. But doing the algebra shows that if you subtract the Hafler rear difference (L-R) signal from the stereo pair, all you have done is swapped left and right:

L-(L-R) = L-L+R = R

R-(L-R) = R-L+R = L

which there are easier ways of doing!
 

Sonik Wiz

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I wondered if I should remove the rear channel signal from the fronts in the latest version of my line level Hafler Decoder. But doing the algebra shows that if you subtract the Hafler rear difference (L-R) signal from the stereo pair, all you have done is swapped left and right:

L-(L-R) = L-L+R = R

R-(L-R) = R-L+R = L

which there are easier ways of doing!
In a passive decoder the rear chs (opposite phase) would be reduced in the fronts by doing simple mixiing in phase between the speakers. This has the obvious side effect of reducing separation up front which doesn't win any popularity contests.
 

chucky3042

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Thanks for the info, Chucky. Actually, my system is wired both ways - I can listen to all channels through a decoder OR the way I described in my post.

The Dynaco method was my first experience with 'surround' sound way back in late 60's. That's where my journey started oh so many years ago.
The Halfer Dynaco was my first method way back in the 70's also!
 

quadsearcher

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Hi Wagonmaster_91

Yes we and most good stereo to surround processors do change the front left and right outputs. In our case we actually remove any rear content from the front signals so if you just wired the fronts direct from the source the net result is a reduced front to rear separation and a reduced surround image. Early simple surround techniques such as the old Halfer Dynaco left the fronts alone and subtracted L-R for the rear content.

I also note for those who insist on the silly center channel that we also remove any center content from the left and right channels and stick it in the wretched center (stupidly under the TV!)

Regards

Chucky
Maybe this needs its own thread, but I've wondered how the original SM can be used in 4.0. I've been using center just so I'm not missing out on anything, but is there some kind of switch or sensor so that when nothing is plugged into center, the center content is then returned to L/R?
 

chucky3042

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Maybe this needs its own thread, but I've wondered how the original SM can be used in 4.0. I've been using center just so I'm not missing out on anything, but is there some kind of switch or sensor so that when nothing is plugged into center, the center content is then returned to L/R?
On the old SM V1 look at the rear RCA panel, the correct left front/ right front outputs are in 2 groups depending on if you are using 4.1 or 5.1. For 4 channel you use the left hand side "front" group.
 

Wagonmaster_91

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In a passive decoder the rear chs (opposite phase) would be reduced in the fronts by doing simple mixiing in phase between the speakers. This has the obvious side effect of reducing separation up front which doesn't win any popularity contests.
Didn't one of the speaker manufacturers back in the late 60's to mid-70's do that very thing (for a stereo pair - had nothing to do with any quad) claiming it actually improved the stereo separation and "3D" imaging? Add some out of phase left signal to the right speaker and vice-versa. KEF? Polk?
 
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Sonik Wiz

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Didn't one of the speaker manufacturers back in the late 60's to mid-70's do that very thing (for a stereo pair - had nothing to do with any quad) claiming it actually improved the stereo separation and "3D" imaging? Add some out of phase left signal to the right speaker and vice-versa. KEF? Polk?
They did not do "that very thing". You were talking about removing rear ch information from the front chs. Polk had a method of expanding 2 ch stereo to wide 180 deg souundfield. Nothing to do with real surround sound or quad as you said . Nothing to do with the in phase blending I mentioned. They have new updated speakers for that today:
Polk L800.
Better off using Involve TSS.
 
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Wagonmaster_91

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I meant the speaker maker design was to feed some out of phase left info to the right speaker (in a stereo only set up) and right out of phase to the left speaker. You had to hook up both speakers with left and right speaker output feeds from your amp. (Sorry for the confusion.)
 

MidiMagic

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I may have asked this question before in a general sense, but since we have someone who actually works for a manufacturer on the QQ I figure I might get a better informed answer. The question is: In surround synthesizer mode(s) (or when a stereo signal is run through the SM and it creates additional channels), does it alter in anyway the original front left and right channels?

I ask this because I use separate amps for my front, rear and surround channels. For that reason, I don't run the front L&R feeds from a decoder back to the front channels amp since that amp is already receiving the front L&R signal from the original source. I figure the fewer devices a signal has to run through, the less chance of signal loss, colorization, distortion, etc. Plus, I like being able to control volume and tone for each pair of channels because as we all know surround mixes can vary widely in their balance of front to rear to surround to height/overhead.

OK, so for those of you who have deep knowledge of the legacy decoders - Tate, Sansui QSDs, AS&IC, Lafayette L or W, EVX-44, Sonys, Fosgates, etc: Do any of those change, add or subtract anything from the front channels when processing a stereo signal to "fake surround" ?

I don't think so. Correct?
Yes, they do.

Most of the fake quad systems were similar to the EV-4 decoder
Sansui partially blended the front.
The "composer" mode in the Lafayette decoders partially blended the front.
The EV matrix (both kinds) had a 20% front blend

Dynaquad is the only system I know of that did not blend or gain-ride the front.

Bose was the manufacturer that had an out-of-phase crossfeed.
 

Soundfield

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The Halfer Dynaco was my first method way back in the 70's also!
It would be good if the Super Surround PreAmp had Hafler as one of its decode options (really simple to do L-R in software - no nasty complex matrix equations to worry about with this one!). I still find its ambience extraction surprisingly effective for a lot of classical music recordings, especially those recorded live. The level controls and rear delay facilties of the preamp would make it useful feature (well for me anyway!). How about it Chucky?
 

chucky3042

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It would be good if the Super Surround PreAmp had Hafler as one of its decode options (really simple to do L-R in software - no nasty complex matrix equations to worry about with this one!). I still find its ambience extraction surprisingly effective for a lot of classical music recordings, especially those recorded live. The level controls and rear delay facilties of the preamp would make it useful feature (well for me anyway!). How about it Chucky?
Interesting thought, I have passed it onto Dave the Bitch
 

3.0

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In a passive decoder the rear chs (opposite phase) would be reduced in the fronts by doing simple mixiing in phase between the speakers. This has the obvious side effect of reducing separation up front which doesn't win any popularity contests.
what if you put the phase only contend to the side of the fronts? would that make any sense?

the idea would be to widen traditional stereo. hearing sound behind me is not my intrest

(the speakers would obviously be towed in)
 

J. PUPSTER

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what if you put the phase only contend to the side of the fronts? would that make any sense?

the idea would be to widen traditional stereo. hearing sound behind me is not my intrest

(the speakers would obviously be towed in)
You would need a stereo decoder for that.
 

Soundfield

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....the idea would be to widen traditional stereo.
You don't need extra speakers to widen the stereo image if that's all you want to do. You just need to mix a little anti-phase crosstalk into each channel. People have been doing that since the sixties! Lots of simple circuits out there (just Google "stereo width control" if you want to build one yourself) - or you can get a kit if you are lazy(!) - for example: Width controller kit.
The only problem is they tend to sound a bit artificial, particularly as the more you widen the image, a greater hole in the centre appears.
 
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