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Speaker Testing: why mono is better

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amirm

amirm

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Here is the problem with stereo testing with the aim of opining on its ability to image well: to the extent there is no objective measurement or even research that backs any such opinion, the stated assessment is simply unreliable. With mono listening with the intent to assess tonality, we have the solid, super reliable frequency response measurements to analyze it. No such thing exists for spatial qualities and as such, you have to believe the reviewer on faith.

On that front, I find the most random commentary on any audio system to be imaging. Folks even say when they change a cable imaging improves! One can't even describe properly what good or great imaging is. If said that "imaging is precise," what is precise to you and the reviewer? And per above, how do you know the assessment is even correct?

Worse yet, it seems to be the height of fashion for a reviewer to comment on imaging. They think if they get this right, it shows they are great listeners. They go on and on about imaging as if it is a sign of authority. Truth and evidence be damned.

I bet you can get any opinion of imaging about any speaker. Mathew commented on this with regards to panel speakers and wide their dispersion is. Myths abound in this area.

For all of these reasons, I completely ignore any subjective remarks when it comes to imaging of speakers. It such an abused and misguided assessment that it does not pay to put any attention on it.

Yes, for headphones I make a binary comment about whether there are, or aren't spatial qualities. But that is about it. I have found some cause and effect there that I hope to develop more but that is about all one can do there. With speakers, even if I did stereo testing, I have no idea how I would address any challenges to my opinion of something imaging well or not.
 

pma

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One may have similar objections to your subjective impressions from listening of female vocals. Once we go subjective we go subjective, period.
 
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amirm

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One may have similar objections to your subjective impressions from listening of female vocals. Once we go subjective we go subjective, period.
So you didn't read my post....
 

Thunder22

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Recently I listened to one speaker. It was a single broken Paradigm active 20 (circa 1998) I bought on Ebay and repaired. While listening I immediately thought of this post. I was amazed at what this one speaker, for it's size, was able do. I'm excited to try some of my other speakers in single (mono) format. It is clear that this would be the best way to audition speakers; wish I would have known about this concept 25 years ago.

Common sense tells us that mono testing is the correct way. Oh wait that's not a thing anymore. I just never knew about the auditioning factor.,

So I say to the "but ya gotta test in stereo, bro" , " we need to know the spatial quality dude" Why do you even come to this site? It has been explained over and over.

Two ears and a brain are more sophisticated than a microphone; at least I used to think so.

Twenty three pages . :facepalm: .
 

dfuller

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Mono is going to tell you much more of the story accurately than stereo will, but am I right or wrong in thinking that dispersion/directivity qualities could affect how we perceive the stereo image?

It certainly seems that way to me in my (very much sighted) listening that narrower dispersion speakers in stereo are a bit more "pinpoint" as to where things are than wider dispersion designs which are a bit more "diffuse". In mono the narrow dispersion speakers seem small vs the wider ones which directly ties in with the narrower beamwidth, but it seems to be less of an issue in stereo... Maybe I'm crazy, I don't know.
 
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amirm

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Mono is going to tell you much more of the story accurately than stereo will, but am I right or wrong in thinking that dispersion/directivity qualities could affect how we perceive the stereo image?
Fifty things contribute to that. Your room, speakers, position, frequency response, exact nature of directivity, content, especially content. This is why no research has come up with good answers to this.
 

JustIntonation

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Mono is going to tell you much more of the story accurately than stereo will, but am I right or wrong in thinking that dispersion/directivity qualities could affect how we perceive the stereo image?

It certainly seems that way to me in my (very much sighted) listening that narrower dispersion speakers in stereo are a bit more "pinpoint" as to where things are than wider dispersion designs which are a bit more "diffuse". In mono the narrow dispersion speakers seem small vs the wider ones which directly ties in with the narrower beamwidth, but it seems to be less of an issue in stereo... Maybe I'm crazy, I don't know.

Yes you're right in thinking wider dispersion designs are more "diffuse" as they radiate more sound into the room.
I personally prefer wide dispersion speakers in a good room. And there has been a slight preference for wide dispersion speakers found in blind testing as well. (and the opposite is clearly true for surround systems)
I think the reason for this is that stereo is a limited format and sound coming from more than two spots is preferred (room reflections) for stereo.
This is also noted in the Audioholics livestream that VintageFlanker posted above.
What was also mentioned in that stream is that in high RT open rooms (like the one Amir auditions in) you'll usually want narrow dispersion speakers as not to excite the room too much. Combine this with the tonal balance effects of listening to mono speakers and I think this explains why in Amir's subjective listening tests he seems to prefer narrow directivity speakers over wide dispersion speakers even when the scoring of these speaker would suggest otherwise. (my small critique of Amir's otherwise fantastic work and reviews)
 

richard12511

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Here is the problem with stereo testing with the aim of opining on its ability to image well: to the extent there is no objective measurement or even research that backs any such opinion, the stated assessment is simply unreliable. With mono listening with the intent to assess tonality, we have the solid, super reliable frequency response measurements to analyze it. No such thing exists for spatial qualities and as such, you have to believe the reviewer on faith.

On that front, I find the most random commentary on any audio system to be imaging. Folks even say when they change a cable imaging improves! One can't even describe properly what good or great imaging is. If said that "imaging is precise," what is precise to you and the reviewer? And per above, how do you know the assessment is even correct?

Worse yet, it seems to be the height of fashion for a reviewer to comment on imaging. They think if they get this right, it shows they are great listeners. They go on and on about imaging as if it is a sign of authority. Truth and evidence be damned.

I bet you can get any opinion of imaging about any speaker. Mathew commented on this with regards to panel speakers and wide their dispersion is. Myths abound in this area.

For all of these reasons, I completely ignore any subjective remarks when it comes to imaging of speakers. It such an abused and misguided assessment that it does not pay to put any attention on it.

Yes, for headphones I make a binary comment about whether there are, or aren't spatial qualities. But that is about it. I have found some cause and effect there that I hope to develop more but that is about all one can do there. With speakers, even if I did stereo testing, I have no idea how I would address any challenges to my opinion of something imaging well or not.

I agree with you in that I basically disregard imaging/soundstage comments when reading/watching reviews(except for a few exceptions).

That said, I definitely do know that dispersion width affects image clarity and precision, and I also have suspicions that wider dispersion becomes more advantageous as the number of channels decreases. Toole even says this himself. He also admits that the Harman stereo tests favor wider dispersion(since they don't toe in the speakers), but he says this is ok because it highlights a real advantage that wider dispersion has(which I completely agree with). This may not translate 100% though for those of us who have complete position/toe-in freedom.

My current opinion is that if you have to choose between mono or stereo, mono should be preferred. However, I also believe there is insufficient evidence to say that stereo and mono preference will always be the same, particularly when the only thing that differs is dispersion width.

*Edit: Haven't watched the Audioholics video yet, so not sure if I agree/disagree with what they have to say.
 
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Tom Danley

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There are aspects about a loud speaker that are audible,you can hear clearly yet do not show up as "something" in measurements.
Some of these are easier to single out in mono or at least that's when the light went on for me at work and I said "wait a second".

Imagine two pairs of speakers, they sound essentially the same if you listen to each one, one at a time.

You play a soft voice AND close your eyes. It is easy to point at the speaker and with one pair of speakers it's easy to guess how far away the speaker is but with the other, it is hard to localize the depth.

If you play a recording that "sounds like" its very far away, it sounds like it's far away or a dry up close voice is in your face. One speaker has a strong spatial identity, the other not so much.
One pair of speakers has simple radiation pattern, the other has complex features that produce differences between the right and left ear that allow your brain to easily localize the depth "as the source". The other speaker with simple radiation presents the same signal where the right and left ears are and so there is no loudspeaker related location information in the sound. In the latter case, the speakers may not even be noticeable in the stereo image where the others are always there in the image, your brain correctly identifying them as sources.
Hope that makes sense
Tom Danley
 

Purité Audio

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Tom great to see you here, when will see is your new Hyperion!
Excuse the off-topic.
Best,
Keith
 
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AdamG

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There are aspects about a loud speaker that are audible,you can hear clearly yet do not show up as "something" in measurements.
Some of these are easier to single out in mono or at least that's when the light went on for me at work and I said "wait a second".

Imagine two pairs of speakers, they sound essentially the same if you listen to each one, one at a time.

You play a soft voice AND close your eyes. It is easy to point at the speaker and with one pair of speakers it's easy to guess how far away the speaker is but with the other, it is hard to localize the depth.

If you play a recording that "sounds like" its very far away, it sounds like it's far away or a dry up close voice is in your face. One speaker has a strong spatial identity, the other not so much.
One pair of speakers has simple radiation pattern, the other has complex features that produce differences between the right and left ear that allow your brain to easily localize the depth "as the source". The other speaker with simple radiation presents the same signal where the right and left ears are and so there is no loudspeaker related location information in the sound. In the latter case, the speakers may not even be noticeable in the stereo image where the others are always there in the image, your brain correctly identifying them as sources.
Hope that makes sense
Tom Danley
Welcome Aboard @Tom Danley.
 

Duke

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One pair of speakers has simple radiation pattern, the other has complex features that produce differences between the right and left ear that allow your brain to easily localize the depth "as the source". The other speaker with simple radiation presents the same signal where the right and left ears are and so there is no loudspeaker related location information in the sound. In the latter case, the speakers may not even be noticeable in the stereo image where the others are always there in the image, your brain correctly identifying them as sources.

Hi Tom, I agree that we don't want the speakers doing things which draw attention to themselves as the sound source, and ime such things are often (if not always) easier to pick out in mono than in stereo. But beyond that I'm not totally clear about what you mean.

What are these "differences between the left and right ear" that you refer to? Is this in the first-arrival sound, or in the reflections (in which case room acoustics comes into play), or both?

Can you provide an example (general or specific) of a speaker which "has complex features that produce differences between the right and left ear that allow your brain to easily localize the depth "as the source""?

And, can you provide an example of the sort of desirable "simple radiation pattern" which enables the speakers to "not even be noticeable in the stereo image"?

Thanks!
 

Tom Danley

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Hi Tom, I agree that we don't want the speakers doing things which draw attention to themselves as the sound source, and ime such things are often (if not always) easier to pick out in mono than in stereo. But beyond that I'm not totally clear about what you mean.

What are these "differences between the left and right ear" that you refer to? Is this in the first-arrival sound, or in the reflections (in which case room acoustics comes into play), or both?

Can you provide an example (general or specific) of a speaker which "has complex features that produce differences between the right and left ear that allow your brain to easily localize the depth "as the source""?

And, can you provide an example of the sort of desirable "simple radiation pattern" which enables the speakers to "not even be noticeable in the stereo image"?

Thanks!
Hi Duke
This issue opens a can of worms and there is more to it than i alluded to.

A friend and former co-worker Doug Jones was involved with research in the 80's that revealed more about how we hear and localize sounds.
The result of that work was a set of recordings which capture / mimic our localization. To be clear this Head Related Transform Function and our ears unique Pinna responses are a key part of localization, it is more than just loudness and precedence in time.

Our outer ears shape produce a frequency response which changes with direction and elevation AND there are two notches which move in frequency with those changes in source direction.

When Doug and friends place tiny microphones deep inside people's ears they saw this comb filtering and plotted it. We do not hear that "combing" as a flaws as it appears to measurement minded, we associate this stuff with source direction.

Here are some recordings Doug Made in the day which exploit this additional aural cue.

https://www.audiocheck.net/audiotests_ledr.php

Unlike an amplitude panned stereo image, these signals can extend well outside the normal speaker coverage as they trick your brain into associating that sound with a location in space. The better your speakers are at preserving stereo information, the more real this sounds.
Funny, now days you even hear TV commercials which exploit this effect, sounds that "sound like" they are floating above or outside your speakers.

While popular lore says we can't hear very fine combing (combing is what you get when you add a delayed signal to an un- delayed signal), THAT kind of combing can "mimic" or interfere with the location combing your ears need to identify locations in space and can create the kind of new radiation that makes it easy to hear or localize the physical depth (with eyes closed).

A few years ago Doug and I taught a class at Avixa / Infocomm, the challenge I was given was make two pairs of speakers that looked and sounded "the same" (even used the same drivers) but radiated and sounded very differently when in stereo. In the class demo, one pair made an ambiguous but appealing "wall of sound" out of Diana Krall and with the other, she was right there in front of you like you could walk up to her.

One pair had as many things as i could think of to make combing in this time / frequency range the other had as little as possible with the same drivers.

There are too many things to list here that can cause these image disrupters but the idea is that until the expanding wave is "large enough" to be self supporting (like how a baffle or horn can confine the angle and project it at more or less the same angle per Keele's pattern loss thumb rule), until that point, it can re-radiate at any point there is an abrupt change in the rate of expansion.

In a typical small speaker this would often be the transition around the tweeter, the edges, the near by drivers and often non-pistonic behavior where some parts are moving one way while others are going the other way etc.. In many multi-way speakers, you have to be far away enough to not localize separate sources but often enough the separate sources make the depth easier to hear as the source .

The up side is that if you want to hear speakers that do a better than average job disappearing into the stereo image, you can do this yourself.
Obtain a pair of these drivers (I know these are good drivers and work for this);

https://faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=401000100

Then cut out a mounting hole in the center of a baffle (use 1/2 inch plywood) at least 2 feet square.

Cover the front side of the baffle with 1/2 inch foam padding (or actual acoustic foam) stuck on with super77 or other casual adhesive.
Then mount the driver from the front side so that it sits in a slight recess of compressed foam around it.

This unusually good 3 inch full range driver is small enough to radiate like a simple piston from a single location in time and space all the way up to several Khz, above that it is a mixed mode (traveling wave something like a soft dome).
The driver mounted this way and eq'd flat up high is more free than most of this "spatial identity" as I think of it and can produce a VERY compelling stereo image without standing out in it....up to the SPL runs out of gas or LF extension. Up close these are very good and at times one is hardly aware of loudspeakers.
You can enclose the back and calculate an "alignment" but if you like them and want to add a subwoofer / bass speaker, use a sealed box for these. Also, there is a 3 element RLC network that takes care of a rising hf although i don't see that in this newer computer. If i run across it I will post the values
At work, these same radiation related aspects of radiation on SQ apply even more so, I believe and I think some of our large systems show it is mostly these radiation / interference issues and not as much driver limitations that limits the effective range and fidelity of large arrays.
Best
Tom
 

Duke

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There are too many things to list here that can cause these image disrupters but the idea is that until the expanding wave is "large enough" to be self supporting (like how a baffle or horn can confine the angle and project it at more or less the same angle per Keele's pattern loss thumb rule), until that point, it can re-radiate at any point there is an abrupt change in the rate of expansion.

In a typical small speaker this would often be the transition around the tweeter, the edges, the near by drivers and often non-pistonic behavior where some parts are moving one way while others are going the other way etc.. In many multi-way speakers, you have to be far away enough to not localize separate sources but often enough the separate sources make the depth easier to hear as the source .


Thank you very much Tom for taking the time to craft an educational reply. I somehow overlooked it until just now.

The up side is that if you want to hear speakers that do a better than average job disappearing into the stereo image, you can do this yourself. Obtain a pair of these drivers (I know these are good drivers and work for this);

https://faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=401000100


Small world - I make several bass guitar cabs which use that little Faital "fullrange" cone for the top end! Here's one of them:

Changeling112.Front.JPG


For the sake of power handling my crossover point is higher than ideal for imaging, but then these are 500-watt bass cabs, not cork-sniffer mini-monitors. A fair number of my customers use them for amplifying upright bass, which is an application in which fidelity matters somewhat. The dispersion of that little cone seems to be a welcome improvement, arguably making it a bit less obvious that you're listening to a box.
 
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Bullwinkle J Moose

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There has been plenty of research into imaging since the 1980's

I would know since it was my research

The problem with great imaging is that it would require a special mic technique and speaker methodology to achieve great results

You will never get great imaging when mastering from a mixing console in a studio, then played through "ANY" pair of speakers

Recording, and playback must be a matched system for realistic imaging

Crosstalk and comb filtering MUST be eliminated for the best results

Mono information must NEVER be reproduced from two or more locations

Omnidirectional speakers also give the best results

Every commercial song you play has a different playback requirement for imaging and width which makes marketing a perfect system impossible

I can create an unbelievably realistic image, but mass production from record to playback is simply not feasible

Every single pair of speakers available are wrong for great imaging as are the recording techniques

They are "good enough" for consumer mass marketing and nothing more

End of Story!
 
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