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Stereo vs mono - what is the ideal frequency response?

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Thomas_A

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So if something is have highest preference in mono (which is flat in anechoic conditions), is has the highest preference also in stereo. But since it sounds different from the mono, it means that there is something better for stereo?
 

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So if something is have highest preference in mono (which is flat in anechoic conditions), is has the highest preference also in stereo. But since it sounds different from the mono, it means that there is something better for stereo?
No I think you are connecting dots which may not be there.

Can you explain what you define as "different"?
 
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No I think you are connecting dots which may not be there.

Can you explain what you define as "different"?

See Shirley et al and Toole. He also admits hearing the effects which starts with a dip in the 1-2 kHz region. Surely that is "different" from a flat response.
 

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Why not, since it gives a timbral effect between 1-10 kHz?
The specific acoustic conditions of any room will affect any speaker. That doesn't mean that a good speaker suddenly becomes bad or a bad one becomes good. The preference remains.

Watch the lecture :)
 
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The specific acoustic conditions of any room will affect any speaker. That doesn't mean that a good speaker suddenly becomes bad or a bad one becomes good.

Watch the lecture.

Agreed about that, but that is not the issue here. The problem is not the room or speaker-room relation, it is purely geometrical due to the stereo vs mono setup.
 

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Agreed about that, but that is not the issue here. The problem is not the room or speaker-room relation, it is purely geometrical due to the stereo vs mono setup.
As I said that will be the case for any speakers, but also an effect specific to layout and the room. It won't suddenly make a bad one good or a good one bad or invalidate the fundamental principle of having a flat anechoic response, even if there is a small degree of timbral change when used stereo, or caused by the room size, shape or other acoustic properties.

Also if you change the response of a speaker to account for any specific stereo timbral effect you are just entering the circle of confusion. Change the position, change the room and you require a different change. You just chase your tail.

Look, you don't have to take my word for it. Please watch the video and note the part where Toole specifically states that stereo does not affect peoples fundamental preference.
 
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As I said that will be the case for any speakers, but also an effect specific to layout and the room. It won't suddenly make a bad one good or a good one bad or invalidate the fundamental principle of having a flat anechoic response, even if there is a small degree of timbral change when used stereo, or caused by the room size, shape or other acoustic properties.

Also if you change the response of a speaker to account for any specific stereo timbral effect you are just entering the circle of confusion. Change the position, change the room and you require a different change. You just chase your tail.

Look, you don't have to take my word for it. Please watch the video and note the part where Toole specifically states that stereo does not affect peoples fundamental preference.

I have read about this already; they are using mono since it is much more revealing. Occasionally they made tests in stereo and there was no preference difference between between which speakers that were preferred. However, the specific experiment has not been adressed. You must take the perfectly flat (preferred one in mono) and make the stereo tests with and without the specific EQ correction in mind, and then make the preference test. Toole avoids this specific question and refers to that stereo is flawed - and suggest to use multichannel instead. That multichannel is a solution is true, but it is not an answer to the specific question.
 

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I have read about this already; they are using mono since it is much more revealing. Occasionally they made tests in stereo and there was no preference difference between between which speakers that were preferred. However, the specific experiment has not been adressed. You must take the perfectly flat (preferred one in mono) and make the stereo tests with and without the specific EQ correction in mind, and then make the preference test. Toole avoids this specific question and refers to that stereo is flawed - and suggest to use multichannel instead. That multichannel is a solution is true, but it is not an answer to the specific question.

He doesnt avoid it he is explicit. To conclude that mono was more revealing they would have had to do plenty of test work with stereo as an alternative.

From the video here:


"without exception", "every time" the mono preference was the stereo preference.

So this tells us that any timbral change from mono to stereo is not significant enough to change the preference.

OK, so what if you have a set up with a 2m x2m x2m triangle and you apply some EQ (whatever that might be). What happens when you change to a 3m x 3m x 3m triangle? The required EQ will be different. So considering the potential variation of set up and room you could have an infinite number of appropriate EQ settings.

However we know from the testing Toole has performed that it doesnt actually matter what room or setup you configure, the preferred speakers remain preferred. Again form the video


So it is clear that the fundamental sound coming from the speaker is the important bit, even though this may get changed by room or set up, mono or stereo.

He talks about how the listener separates the timbral sound of the speaker from the room etc.
 
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He doesnt avoid it he is explicit. To conclude that mono was more revealing they would have had to do plenty of test work with stereo as an alternative.

From the video here:


"without exception", "every time" the mono preference was the stereo preference.

Again, this is done testing various speakers with their individual responses. You need to have explicit control of the specific EQ required to adjust for the mono- to stereo-errors.
 
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He doesnt avoid it he is explicit. To conclude that mono was more revealing they would have had to do plenty of test work with stereo as an alternative.

From the video here:


"without exception", "every time" the mono preference was the stereo preference.

So this tells us that any timbral change from mono to stereo is not significant enough to change the preference.

OK, so what if you have a set up with a 2m x2m x2m triangle and you apply some EQ (whatever that might be). What happens when you change to a 3m x 3m x 3m triangle? The required EQ will be different. So considering the potential variation of set up and room you could have an infinite number of appropriate EQ settings.

However we know from the testing Toole has performed that it doesnt actually matter what room or setup you configure, the preferred speakers remain preferred. Again form the video

Well it is somewhat related to the angle of the speaker hitting you, not so much the size of the triangle. As all things this is an average deviation of +/- 2 dB in a normally reflected room for the phantom centre, and will be compromised to even less adjustment so for pure left-right signals. EQ is between 1-2 dB between 1-2 kHz, and dip of 1-2 dB between 2-5 kHz and 7-8 kHz
 
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Below is the specific answer to the stereo dilemma from Floyd Toole:

"Ah, the dilemma of stereo. It is a fundamentally flawed delivery system and no amplitude panned phantom image created by sounds radiated by both loudspeakers can sound the same as, or as "accurate" as, sound radiated by a single loudspeaker. This is discussed at length in my book, starting with the obvious 2 kHz octave wide cancellation dip caused by acoustical crosstalk. When stereo is compared to mono listening - see section 7.4.2 in the 3rd edition - people were much more sensitive to loudspeaker faults in mono, but interestingly enough simple pop music was similarly revealing in that there were two "mono" sound sources - the hard panned left and right images. Classical music and pop with high production values generate enough spatial information to distract from many common small timbral faults. Spatial effects rank with timbral accuracy in our evaluations of sound quality. Obviously, one should start with neutral loudspeakers and let the chips fall where they may.

Even at my age, with accumulated hearing degradations, I can hear these effects and although I still derive pleasure from the music it grieves me that in 2019 we still are listening to the first improvement on mono - from the 50s! Will it never end?"
 

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Well it is somewhat related to the angle of the speaker hitting you, not so much the size of the triangle. As all things this is an average deviation of +/- 2 dB in a normally reflected room for the phantom centre, and will be compromised to even less adjustment so for pure left-right signals. EQ is between 1-2 dB between 1-2 kHz, and dip of 1-2 dB between 2-5 kHz and 7-8 kHz
So, as I have already alluded to you cannot come up with definitive EQ for a speaker. You just end up chasing your tail. Circle of confusion.

Rooms and set up can have a big effect on the sound but regardless the preferred speakers, ones that have flat anechoic response with smooth off axis response remain preferred.
 
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So, as I have already alluded to you cannot come up with definitive EQ for a speaker. You just end up chasing your tail. Circle of confusion.

Rooms and set up can have a big effect on the sound but regardless the preferred speakers, ones that have flat anechoic response with smooth off axis response remain preferred.

Well yes, I just gave you the EQ figures which are based on the timbral errors given in Shirley et al.
 

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Below is the specific answer to the stereo dilemma from Floyd Toole:


Obviously, one should start with neutral loudspeakers and let the chips fall where they may.

This doesnt contradict what I have said. All it does is confirm that stereo is flawed, it screws things up to a degree. It doesnt mean that trying to EQ the generated flaws is a good idea or will lead to better sound, in fact his final comment says dont mess with it.
 
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This doesnt contradict what I have said. All it does is confirm that stereo is flawed.

It does not contradict what you said, agreed. But again Toole admits that the stereo speaker setup cannot sound the same as the mono speaker, but avoids the question whether it can be partly compensated for. The compromise in his opinion is to start a neutral speaker and leave the errors as they are. The alternative way, start with a neutral speaker and adjust the small errors is another solution. Scientifically, there is no definitive answer since the experiment has not been performed.
 

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It does not contradict what you said, agreed. But again Toole admits that the stereo speaker setup cannot sound the same as the mono speaker, but avoids the question whether it can be partly compensated for. The compromise in his opinion is to start a neutral speaker and leave the errors as they are. The alternative way, start with a neutral speaker and adjust the small errors is another solution. Scientifically, there is no definitive answer since the experiment has not been performed.
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.
 
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Well he is explicit elsewhere that messing up a good fundamental 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.

Still, the specific experiment has to my knowledge not been performed or published. The dip is partly filled in by room reflections; and the peaks between 2-5 kHz and around 8 kHz should not be difficult to EQ.

You can even infer that the Revel M106 and M116 speakers have such a stereo compensation already. A coincidence or intended?
 

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Still, the specific experiment has to my knowledge not been performed or published. The dip is partly filled in by room reflections; and the peaks between 2-5 kHz and around 8 kHz should not be difficult to EQ.

You can even infer that the Revel M106 and M116 speakers have such a stereo compensation already. A coincidence or intended?
You don't need to do the experiment to know you can't rectify a cancellation. Also it's a moot point because as you allude to, room reflections affect the situation. You can't define a specific correction as it would need to be different in every single room and every listening position, as I mentioned previously.

The only thing to do, and correct thing to do, is have a neutral speaker. You shouldn't mess the speaker up because stereo creates problems
 
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