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Stereo vs mono - what is the ideal frequency response?

Duke

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Except for pure 2-microphone stereo recordings, having a center channel feed/speakers removes from the L/R speakers most of the center information that would otherwise be mixed into them. That mixing is never perfect and the most obvious improvement on going from 2channel to 3channel is usually an increase in soundstage width and clarity due to the deletion of that material.

I can see soundstage clarity being enhanced by having the center channel information removed from the left and right front speakers, but how is soundstage width increased? Does it now extend laterally beyond the left and right speakers, whereas before it did not? And if so, what causes that?
 

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In such a case, why did not the Harman blind tests of stereo recordings using a single mono speaker notice this?

The goal of the blind tests was to determine if measurements could predict listener preferences. The model is not perfect, but it worked well enough for the questions that they wanted to ask. Results did not change between mono vs. stereo listening.
 

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Well he is explicit elsewhere that messing up a good fundamental on axis frequency response is a bad idea.

Also referring to a "cancellation dip" implies that no it cant be compensated for. Crank up the amplitude at the affected frequencies and they will still cancel.

For a cancellation dip to imply it can't be compensated for, there must be perfect cancellation. Measurements show that it is not perfect cancellation. Therefore you can compensate for it.
 
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Thomas_A

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The goal of the blind tests was to determine if measurements could predict listener preferences. The model is not perfect, but it worked well enough for the questions that they wanted to ask. Results did not change between mono vs. stereo listening.

This has been stated previously. Still there is an audible difference between the mono and stereo situation. So there is room for more experiments here.
 

Kal Rubinson

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I can see soundstage clarity being enhanced by having the center channel information removed from the left and right front speakers, but how is soundstage width increased? Does it now extend laterally beyond the left and right speakers, whereas before it did not? And if so, what causes that?
I don't have any answers for you. Aside from my speculation that the effects are possibly due to the removal of center channel info from the L/R speakers, these are only observations, albeit from a number of listeners. Try it.
 

Fitzcaraldo215

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I can see soundstage clarity being enhanced by having the center channel information removed from the left and right front speakers, but how is soundstage width increased? Does it now extend laterally beyond the left and right speakers, whereas before it did not? And if so, what causes that?
I have been a frequent Mch listener over more than the past decade. I greatly prefer it.

With a proper center channel, it Is my impression that the center or the soundstage fills from the inside out rather that the outside in for stereo. The Floyd Toole HRTF differences from speakers may give you an insight when he speaks of a center channel.
 
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Fitzcaraldo215

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I don't have any answers for you. Aside from my speculation that the effects are possibly due to the removal of center channel info from the L/R speakers, these are only observations, albeit from a number of listeners. Try it.
Kal -

That‘s the impression I have. I love it.
 

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For a cancellation dip to imply it can't be compensated for, there must be perfect cancellation. Measurements show that it is not perfect cancellation. Therefore you can compensate for it.
Even with partial cancellation you end up chasing your tail pumping higher amplitudes in and not getting very far. Also the nature of the cancellation will change with small movements in position of the listener. You will also start changing the off axis sound if you do so.
 
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Duke

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I don't have any answers for you. Aside from my speculation that the effects are possibly due to the removal of center channel info from the L/R speakers, these are only observations, albeit from a number of listeners. Try it.

With a proper center channel, it Is my impression that the center or the soundstage fills from the inside out rather that the outside in for stereo. The Floyd Toole HRTF differences from speakers may give you an insight when he speaks of a center channel.

Thank you both.

I'm familiar with Toole's position on the benefits of a center channel, which aside from the obvious (dialog anchoring for off-center listeners) includes not having that 2 kHz dip.

What I'm trying to understand is, how the soundstage becomes wider when the center channel information is removed from the left and right speakers. Kal, could the soundstage widening be attributable to side and/or rear channel contributions? Or have you heard it in the absence of the surround channels?
 

Kal Rubinson

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What I'm trying to understand is, how the soundstage becomes wider when the center channel information is removed from the left and right speakers. Kal, could the soundstage widening be attributable to side and/or rear channel contributions? Or have you heard it in the absence of the surround channels?
Exactly, this is a comparison of a two-channel recording made from a 3(+) channel source and a 3channel recording from the same source. The only difference is that the center feed is not apportioned and mixed into the L/R channels.

As I said, try any of the RCA Living Stereo SACDs.
 

Duke

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Exactly, this is a comparison of a two-channel recording made from a 3(+) channel source and a 3channel recording from the same source. The only difference is that the center feed is not apportioned and mixed into the L/R channels.

Very interesting! Thanks!
 

Kal Rubinson

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Exactly, this is a comparison of a two-channel recording made from a 3(+) channel source and a 3channel recording from the same source. The only difference is that the center feed is not apportioned and mixed into the L/R channels.
As I said, try any of the RCA Living Stereo SACDs.
Very interesting! Thanks!
Please note that many of these particular recordings still are regarded as representative of the Golden Age of Stereo. We are not talking about crummy recordings or ones that cried out for remastering although these are remasters. I was fortunate to spend a day up at SoundMirror where the remasters were done and sit in with Mark Donohue as he worked on them. I learned a lot about listening.
 

test1223

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Hello,

interesting discussion!
In such a case, why did not the Harman blind tests of stereo recordings using a single mono speaker notice this?
From my point of view all such small deviations aren't properly researched, yet. They are over-shadowed by much bigger deviations form different speaker designs.

As you stated correctly there are changes in preference, if you listen in mono or stereo, but these changes are over-shadowed by other issues. There are much more flaws with testing only in mono like a wider DI is preferred and some qualities are not represented properly. And fixing the issue with an eq is most of the time wrong, since you change the direct and reflected sound at the same time and the mastering engineer should already adjust the overall tonality right (in an ideal world). You can experiment with such compensation in the speaker design by changing the direct sound only. But since everything is room related you need the right room for the speaker...

There are plenty other stereo related issues which make it hard to build a very good sounding system e.g. how to create a sense of space or "surrounding sound" with stereo...

Best
Thomas
 

Soniclife

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In such a case, why did not the Harman blind tests of stereo recordings using a single mono speaker notice this?
You would need to know the exact test material used to be sure, but based on Dr T knowing stuff my guess is this was factored into the mono and the stereo test signals used.
 
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