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Speaker Testing: why mono is better

whazzup

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I think channel matching is an important metric for speaker quality, since we do tend to buy them in pairs. I'm not sure how best to test channel matching or what would be an adequate test short of doing the Klippel scan twice, but it does require obtaining a matched pair.

Isn't that more to do with the consistency of individual channel amplification (of the amp)? And the manufacturing tolerance for each speaker?

And remember that a lot of studio monitors are sold per piece....
 

Daverz

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Isn't that more to do with the consistency of individual channel amplification (of the amp)? And the manufacturing tolerance for each speaker?

And remember that a lot of studio monitors are sold per piece....

The idea is to test manufacturing tolerance for the samples. You can at least discover a poor match. You could use the same amp channel for testing (though I'm sure Amir can also verify the consistency of his amplification channels). Some manufacturers do do QC on each pair. I know Vandersteen does this.
 

Vaskis

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I think channel matching is an important metric for speaker quality, since we do tend to buy them in pairs. I'm not sure how best to test channel matching or what would be an adequate test short of doing the Klippel scan twice, but it does require obtaining a matched pair.
As far I understand, quality control of speaker production are on play here, it means all units must have the same qualities/ FR properties. I actually think that some of not so good results here are because of possible quality issues with QC (high/low tolerances). Which again is good, because any consumer can buy "defected" unit. This is also reason why every unit which is sent from manufacture and preform perfect, better that everyone expected could be carefully prepared, so I'm thankful that @amirm always states from where comes test unit. Example with cheap Sony headphones in shop line, perfect, everyone could be in his place and make the same purchase.
If you have ever heard sport equipment reviewer/ tester - https://www.dcrainmaker.com/, he always buys his test units by himself, except for pre-production/prototype units. All normal units received from manufactures are sent back. It's always are mentioned in reviews.
Returning to audio, of course, there are variables up the stream in amplification, dac's and so on. As we can see on @amirm test graphs both channels rarely show exact the same results, yes, differences are mandatory but in extreme cases when all elements in chain tent to one side this could be a problem. It's a guess anyway.
Thanks to @hardisj meassurments sooner or later we will see possible "batch" problems, if there are some. And I believe that in real world there are.
 
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ROOSKIE

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How would 2 speakers make imaging, phase issues, distortion, etc any different than a single speaker? If anything wouldn't comparing the speaker in mono make any of these issues easier to discern than in stereo where they may be masked?

Is there some sort of interaction between identical speakers that only exists when listening to 2 of them? And why is 2 the magic number? I personally listen to my front 3 speakers for music and many people listen in 5.1/7.1/atmos, using this logic we will only spot these differences when listening this way.
I have had many speakers in my space. All of the stereo pairs image, it is stereo after all. (I am using a 2 channel stereo set-up)
I would say there are very distinct differences that are quite meaningful in the way that imaging is presented.
All my "good" speakers image well but they don't all image in the same way in my set-up, some are more diffuse and others more pinpoint. Some speakers do disappear for me more than others, some speakers have a large sweet spot and others narrower.
The number of variables than can affect this part of listening is large, so outside of listening for oneself in ones own room, I see no way to associate a test for it here. It is very subjective. Some people value imaging above all else and others think it is uninteresting.

It seems mono testing gets one ready to buy a low distortion, well made, tonally correct speaker with directivity as measured. Then one simply has to try the pair on their own to see if other factors come into play in the final push. (soundstage, imaging, room interactions, subjective preferences, ect) Obviously a lot of the data here can give you a good idea of what might happen when listening in stereo.

I think 2 channels is the lowest whole number above one - that is why stereo. Back in the day managing the extra channels was harder than now and getting folks on board to buy was an issue. Most musical recordings are still designed for 2 channels or less.
I suppose that as you add extra channels the variables are still there but maybe masked more due to the extra sources and complex interactions. Someone mentioned car tires, if one tire is bad on an 18 wheeler you can still drive across the country but on a motorcycle one bad tire and game over until it is fixed.
You read stories of someone realizing mid movie that their R rear channel wasn't working and not as many stories about some realizing halfway into an album in a 2 speaker stereo set-up that their L channel wasn't working.

For myself there is just something elegant about the imaging that 2 speakers create.
 

ROOSKIE

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Exactly.
With poorly matched loudspeakers, a solo instrument or speaker will drift about left to right depending on the frequenc(ies) being reproduced and not form a solid image. Close matching, and the image will be stable, and won't drift about. The accuracy of timbre will be dependent on the frequency response of the pair, but the pair matching is what determines stereo phantom imaging. Manufacturers in the past used to quote pair-matching accuracy as part of the specification, but I don't see that as common any more.

One might remember that one aspect of BBC licenses for loudspeaker manufacturers was that the BBC could buy a quantity of loudspeakers, put them into stores, then users could take any two, didn't need to be concerned about serial numbers or date of production, and use them as a stereo pair with the pair matching being good enough.
S.

It may not be as much of an issue with modern manufacturing tolerances being so exact. (barring a defective part of course)

I have checked several pairs of speakers recently as part of normal testing and they were all so close.

I just tested a pair of Infinity R152 monitors, $129.99. The pair has almost no variance. They are less than +/- 0.5db. The slight potential variation in how I set them on the measuring stand could be affecting them more than anything. Is this a better than average pair or the new normal, I don't know. Really impressive though for such cheap speakers.

Even measuring them on the Kipple, if they were not exactly aligned the same, that variation may affect the test more than the manufacturing variances - who knows.

Obviously I can not speak for the whole industry or even anywhere close at all.
I can say the variation on all the pairs of speakers I have tested recently has seemed tight enough to be a non-factor. Even my DIY stuff is so close.
 

Spocko

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Because in real life, people don’t listen to one speaker. The interaction between two speakers—in essence, their ability to convey the space of the recording, commonly called imaging—is something important to most consumers and cannot be evaluated using one speaker. In essence, people don’t listen that way, and the subjective component to any review should be at least a little bit useful. By listening to only one speaker, your subjective review is completely useless to the consumer.
It’s not only “bonkers,” as you said, it’s just silly.
And this goes to the very heart of the Mono vs Stereo debate. TLDR: The core premise and the true value of mono speaker reviews is that the virtues and deficiencies audible in mono is more important than the additional qualities that can only be heard in stereo because those stereophonic virtues alone cannot save a speaker that sounds terrible in mono.

Mono is not "better" per se but rather mono represents the most important stack whereas stereo layers additional qualities to consider. Let's break it down into the virtues of each and why one can co-exist with the other, but more importantly, why mono is a bit better than stereo in predicting listener preferences: (1) Listening in mono offers a pure assessment of what listeners HATE about a speaker - the highs are too sibilant, screeching, "etched", etc. But this assessment does not detract from (2) your sentiment about the unique qualities of stereo listening and how "in real life people don't listen to one speaker" but the "interaction between two speakers... their ability to convey space, etc." So let's discuss these 2 issues separately in order to avoid conflating the benefits and shortcomings of each.
  1. Mono is the best way to evaluate the flaws and virtues of the frequency response curve and audible distortions of a speaker design. We can all agree that listening in mono allows us to compare and isolate each speaker's individual deficiencies without worrying about stereophonic speaker interaction like soundstaging, imaging, depth, etc. Additionally, mono listening is not limited to on-axis only, but can also be done off-axis at various angles in order to create a fuller assessment of the speaker because speakers are often adjusted for toe-in to improve the sound - old school approach to equalization.
    1. Mono can fairly determine the subjective appeal of a speaker's FR fingerprint, its signature sound.
    2. A speaker that ranks highly in mono will have a similar FR curve in stereo. Again, not talking about soundstaging or imaging, just the subjective rating of these qualities that are available in mono: FR, decay, distortion, etc.
    3. The controversial part: people place more importance on the appeal of these qualities that are audible in mono over the unique qualities only audible in stereo. Let's talk about that next.
  2. Real life requires the interaction of 2 speakers to convey space, imaging, soundstage, etc. because music sources were mastered for stereo, so therefore 2 speakers are required to assess the "stereo experience". I completely agree that the manner in which two speakers interact offers yet another layer for listener enjoyment not offered by the mono speaker experience (soundstage, imaging sweet spot, depth, etc.). However, the core issue we must discuss is whether these unique stereo qualities are so good that they can overcome the speaker flaws identified in #1 above? Perfect example is the HSU Research CCB8 co-axial speakers which were designed to be listened off-axis (extreme toe-in) because on-axis the highs are unbearably sibilant. The FR curve bears this out:

ccb8 FR.PNG


However, this was designed intentionally because in order to get the widest phantom channel sweet spot possible, it must be toed in between 15 and 25 degrees which requires that they raise the high frequencies a bit to offset this toe-in so that it sounds flat when listened with this extreme toe-in. But the question is this: would the mono assessment of this speaker have been wrong to conclude that it sounded too sibilant and etched? How many consumers would listen to this speaker without proper toe-in? More importantly: is the value proposition offered by the larger phantom sweet spot greater than that of an alternative pair of speakers with a smaller sweet spot but more pleasant sounding FR at most any position? Given the large selection of $700 speakers, I dare say there are at least 2 others that measure better, sound better in mono, and despite the smaller sweet spot, would be preferred by most people with the exception of the edge case that requires the wide sweet spot.
 

sergeauckland

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It may not be as much of an issue with modern manufacturing tolerances being so exact. (barring a defective part of course)

I have checked several pairs of speakers recently as part of normal testing and they were all so close.

I just tested a pair of Infinity R152 monitors, $129.99. The pair has almost no variance. They are less than +/- 0.5db. The slight potential variation in how I set them on the measuring stand could be affecting them more than anything. Is this a better than average pair or the new normal, I don't know. Really impressive though for such cheap speakers.

Even measuring them on the Kipple, if they were not exactly aligned the same, that variation may affect the test more than the manufacturing variances - who knows.

Obviously I can not speak for the whole industry or even anywhere close at all.
I can say the variation on all the pairs of speakers I have tested recently has seemed tight enough to be a non-factor. Even my DIY stuff is so close.

My experience has been rather different. Variations of several dB when measured on-axis, mostly around crossover frequencies, but also elsewhere. Very good loudspeakers manage to be within 1dB from 100Hz to 15kHz, but many more are likely to have variances of several dBs.

If current loudspeakers are normally within 0.5dB variation, then indeed, it's no longer an issue, but how would we ever know unless we see the graphs?

S
 

bennybbbx

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in speaker tests on other pages the testers tell if the stereo width is width or not and they hear depth of field good or not. I hear lots diffrence in stereo width depend on the speaker size i have. And my tests show it happen that slow speakers in mid range reduce the room size feeling and stereo width. all sound smaller as hear thru a door when you can hear ITD. when people not hear ITD, then i think it doesnt matter if mid range fast or not. if you can hear ITD can check in this video
Now i have order a Monacor RBT-35SR ribbon tweeter.
https://www.monacor.com/products/pa...and-speaker-building/hi-fi-tweeters/rbt-35sr/


This reach 85 db at 500 hz seem because it look as a ribbon tweater horn. so enough volume for me and i do crossover at 600 hz when i have. it. maybe this give even more stereo width and reach headphone transients. i hear whats happen in stereo.
 
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amirm

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It seems to me if you're using music you're familiar with on a stereo system, downmixing would be preferable because potentially you're a) losing information you're used to hearing and b) the apparent balance of the mix would be off?
As long as the channel you are using has the content you want to test with, it doesn't matter what the other channel has in it. The content is just a "test signal." There was a time when heavy panning of instruments were used but these days, both channels more or less have the same spectrum of content in them.
 

Midwest Blade

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Would mirror image laid out loudspeakers have any affect? I have two pair of bookshelf speakers from the same maker, same drivers but different enclosures, the better ones are mirror image, the second pair not, they pretty much sound identical.
 
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amirm

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By listening to only one speaker, your subjective review is completely useless to the consumer.
??? That was the whole purpose of the research I showed in the video. That no ranking changed from mono to stereo testing and so results absolutely apply to the end consumer. Seeing how Harman testing these days are in mono, your logic would say that they have been building the wrong speakers and no consumer would like them. We know that is not true.

Just like measurements are a shortcuts to get more accurate results, mono listening tests allow humans to be better evaluators of speakers. The only reason then to ask for stereo listening evaluation is to like less accurate information about how good a speaker is!
 
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amirm

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Would mirror image laid out loudspeakers have any affect? I have two pair of bookshelf speakers from the same maker, same drivers but different enclosures, the better ones are mirror image, the second pair not, they pretty much sound identical.
I place such speakers in the location they need to go. So left speaker gets listened to in the left position. Other than that, no, there is no difference. We listen for proper tonality, dynamic range, etc. that we can determine with one speaker very well.
 
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amirm

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That also applies to headphones why is headphone testing done in stereo then?
The interaction between speakers does not exist with headphones as the sound is isolated in each cup. That said, at some point I do plan on testing in mono to see if it works better. So far, I find them very easy to characterize compared to speakers in stereo so the need has not been there.
 
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amirm

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I think channel matching is an important metric for speaker quality, since we do tend to buy them in pairs.
There is no way to determine slight channel mismatch in stereo listening. Instrumentation is the only useful tool here. Of course, with different positioning -- even if it is an inch or two -- you create your own mismatch. Auto-EQ systems correct for these (both levels and distance).

Also, many speaker companies match to 0.5 dB their higher end lines.

Finally, even if I tested for matching, how would that apply to your pair?
 

ashegedyn

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And this goes to the very heart of the Mono vs Stereo debate. TLDR: The core premise and the true value of mono speaker reviews is that the virtues and deficiencies audible in mono is more important than the additional qualities that can only be heard in stereo because those stereophonic virtues alone cannot save a speaker that sounds terrible in mono.

Mono is not "better" per se but rather mono represents the most important stack whereas stereo layers additional qualities to consider. Let's break it down into the virtues of each and why one can co-exist with the other, but more importantly, why mono is a bit better than stereo in predicting listener preferences: (1) Listening in mono offers a pure assessment of what listeners HATE about a speaker - the highs are too sibilant, screeching, "etched", etc. But this assessment does not detract from (2) your sentiment about the unique qualities of stereo listening and how "in real life people don't listen to one speaker" but the "interaction between two speakers... their ability to convey space, etc." So let's discuss these 2 issues separately in order to avoid conflating the benefits and shortcomings of each.
  1. Mono is the best way to evaluate the flaws and virtues of the frequency response curve and audible distortions of a speaker design. We can all agree that listening in mono allows us to compare and isolate each speaker's individual deficiencies without worrying about stereophonic speaker interaction like soundstaging, imaging, depth, etc. Additionally, mono listening is not limited to on-axis only, but can also be done off-axis at various angles in order to create a fuller assessment of the speaker because speakers are often adjusted for toe-in to improve the sound - old school approach to equalization.
    1. Mono can fairly determine the subjective appeal of a speaker's FR fingerprint, its signature sound.
    2. A speaker that ranks highly in mono will have a similar FR curve in stereo. Again, not talking about soundstaging or imaging, just the subjective rating of these qualities that are available in mono: FR, decay, distortion, etc.
    3. The controversial part: people place more importance on the appeal of these qualities that are audible in mono over the unique qualities only audible in stereo. Let's talk about that next.
  2. Real life requires the interaction of 2 speakers to convey space, imaging, soundstage, etc. because music sources were mastered for stereo, so therefore 2 speakers are required to assess the "stereo experience". I completely agree that the manner in which two speakers interact offers yet another layer for listener enjoyment not offered by the mono speaker experience (soundstage, imaging sweet spot, depth, etc.). However, the core issue we must discuss is whether these unique stereo qualities are so good that they can overcome the speaker flaws identified in #1 above? Perfect example is the HSU Research CCB8 co-axial speakers which were designed to be listened off-axis (extreme toe-in) because on-axis the highs are unbearably sibilant. The FR curve bears this out:

View attachment 119918

However, this was designed intentionally because in order to get the widest phantom channel sweet spot possible, it must be toed in between 15 and 25 degrees which requires that they raise the high frequencies a bit to offset this toe-in so that it sounds flat when listened with this extreme toe-in. But the question is this: would the mono assessment of this speaker have been wrong to conclude that it sounded too sibilant and etched? How many consumers would listen to this speaker without proper toe-in? More importantly: is the value proposition offered by the larger phantom sweet spot greater than that of an alternative pair of speakers with a smaller sweet spot but more pleasant sounding FR at most any position? Given the large selection of $700 speakers, I dare say there are at least 2 others that measure better, sound better in mono, and despite the smaller sweet spot, would be preferred by most people with the exception of the edge case that requires the wide sweet spot.

Sorry - maybe I missed something.
"And this goes to the very heart of the Mono vs Stereo debate. TLDR: The core premise and the true value of mono speaker reviews is that the virtues and deficiencies audible in mono is more important than the additional qualities that can only be heard in stereo because those stereophonic virtues alone cannot save a speaker that sounds terrible in mono.
...."
Doesn't the data for preference show the opposite. The stereo pair sounds better than mono. Isn't the point that mono testing allows one to distinguish the flaws more easily? Stereo apparently masks or makes things harder to distinguish. The bad speakers sound better in stereo no? That was shown in one of the slides.
 

Daverz

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There is no way to determine slight channel mismatch in stereo listening.

I'm not making an argument for stereo listening. Anyway, I think the YT cranks are making everyone feel quarrelsome, so I don't see any point in pressing the issue.
 

Mnyb

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Thankyou for the nice educational video :) btw i doubt that all naysayers in this tread actually watched it ? have ordered Dr Floyds Tooles book to read more about it .
Btw if someone does not know how teams work it's not only toole olive and harman there is a bunch of people in such teams and the "spinorama" seems to have been elevated to a standard.

As can be seen here on ASR speaker brands that are directly in fierce competing with "harman brands" also build speakers close to this research.
There are choices to be made and for example genelec and KEF and many others have their own slant to it. But its a kind of convergent evolution that tells me that these ideas have a real strength .
 

Vasr

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And this goes to the very heart of the Mono vs Stereo debate. TLDR: The core premise and the true value of mono speaker reviews is that the virtues and deficiencies audible in mono is more important than the additional qualities that can only be heard in stereo because those stereophonic virtues alone cannot save a speaker that sounds terrible in mono.
That is only one half of the evaluation. Let us say you have two speakers that don't sound terrible in mono. What can you say about how they sound while used in stereo as they typically are? Will both sound the same or very different in a way that cannot be inferred from a mono evaluation. This is the crux of the question.

So, it depends on the goal. Are you trying to detect "anomalies" in a speaker or are you trying to objectively measure/quantify the audible qualities of a device? This is why I keep saying that you can take a review here as a spectator sport of relative grading (former goal) or as a buying guide based on measurements (latter goal). Two entirely different goals that cannot be conflated with each other or assume one necessarily implies the other.

Moreover, I am not even sure the bolded portion above is necessarily true. There is no binary of "terrible" and "not terrible". There are various grades of deviations in multiple dimensions. So, the "stereo" effect may mask some degree of "terrible" but not some other degree of terrible. Unless you quantify and establish a threshold for the latter, you cannot assume any degree of terrible isn't masked by stereo.

(1) One can say measuring stereo is difficult or that there is no standardized way to set up and test a stereo speaker. That may be so but it doesn't imply the testing in stereo isn't necessary or useful.
(2) One can say that two speakers that measure the same in mono (which is entirely theoretical since no two speakers will ever measure the same) won't sound any different in stereo. While, there may be some justification for this in electronics, it becomes a lot more tenuous in evaluating speakers since there is no such thing as a perfect/transparent speaker.

So the whole argument for the case of mono testing boils down a very flawed and artificial constraint on the speaker behavior.

A speaker so terrible that stereo won't save it (and so stereo isn't necessary) but not so terrible that only mono measurement can expose it (and so mono is necessary).

At best, that seems like a self-serving rationale for (1) above. :D
 

Spocko

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Sorry - maybe I missed something.
"And this goes to the very heart of the Mono vs Stereo debate. TLDR: The core premise and the true value of mono speaker reviews is that the virtues and deficiencies audible in mono is more important than the additional qualities that can only be heard in stereo because those stereophonic virtues alone cannot save a speaker that sounds terrible in mono.
...."
Doesn't the data for preference show the opposite. The stereo pair sounds better than mono. Isn't the point that mono testing allows one to distinguish the flaws more easily? Stereo apparently masks or makes things harder to distinguish. The bad speakers sound better in stereo no? That was shown in one of the slides.
It's not so much that the bad speakers sound "better" in stereo, but in stereo you are adding stereophonic qualities not available to the mono listening experience: soundstage, stereo imaging, depth, etc. The bad sounding speaker in mono still sounds bad in stereo, but the additional stereophonic effects serves as a distraction that mutes the bad qualities with amazing realistic imaging. How many reviews have we read where the author says something like, "Soundstage was amazing, imaging was so real, but after a while the sound was fatiguing." This gets to the heart of why mono is the better way to review speaker performance. You can identify the qualities the make a speaker fatiguing or "bright" or "dark" in mono, and it is these qualities that give the speaker lasting value rather than its stereophonic affects when paired up.
 
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