Speaker Testing: why mono is better

[MerlinGS]

So if a manufacture thought they don't need to put a tweeter in a speaker and it should only play to 5 kHz, you would be assuming that is the right thing to do?

Well, there is that contingent of audiophiles that swears by the use of single, full range drivers, powered by SE low wattage tube amps.

 

[Blumlein 88]

Well, pink noise is more effective for assessing tonal balance than music.

The problem is that we listen to music not pink noise, and we listen in stereo not mono so perhaps tonal balance may not be all that matters.

Unless you’re lazy.

But does evaluating frequency response with pink noise cause us to pick speakers that sound wrong when listening to music? I not aware of that being the case. So for quick evaluations of FR pink noise seems okay to me. You could even do it in stereo if you wish. Might want to use non-correlated noise to help with the comb filtering.

One real problem with music, is some deviations flatter some types of music and not others. Maybe if you listen to only the one flattered music that is better than flat FR. But usually for good results on multiple types of sources a good flat FR seems to be a good thing if you ask me.

 

[DonH56]

Hmph. I only skimmed a few counter arguments, which seem to be along the lines of "I didn't watch the video, but I know it's wrong. And so is Toole, though I didn't really read his research." Fortunately speaker testing ages ago proved to me the benefit of mono testing, but I never wrote a paper about it, so it didn't happen. And you wouldn't care anyway.

 

[richard12511]

Although I agree with many of the assumptions and conclusions in Toole's (and by extension Amirm's) argument regarding speaker testing, if memory serves, there is a problem with his methodology. Imaging was not a variable listeners were trained to evaluate. In this context, a speaker with excellent frequency response, constant directivity, and wide dispersion would be advantaged against a speaker with excellent frequency response, controlled directivity and somewhat wide dispersion. Assuming no serious performance problems with either speaker, the wide dispersion speaker would be preferred if the emphasis is placed in a sense of "broad space"; however, if the emphasis is placed on imaging, the speaker with controlled directivity would be preferred since it should image better. Yes, there are many assumptions here, but they are being used to highlight the presumed bias against imaging.

Imaging was included as part of "Spatial Quality". Spacial Quality is essentially imaging and envelopment grouped together, which makes a lot of sense when usually you have to trade one for the other. The speaker with higher spatial quality is the speaker with the better balance of soundstage width and image precision/clarity. I like it better than having having three different categories.

 

[pozz]

One real problem with music, is some deviations flatter some types of music and not others. Maybe if you listen to only the one flattered music that is better than flat FR. But usually for good results on multiple types of sources a good flat FR seems to be a good thing if you ask me.

Bingo.

 

[Coach_Kaarlo]

Victor/JVC SX-1000 Laboratory (the model name is printed at the bottom of the speaker, so no points).

Every speaker has a point far enough away where the drivers will sum. You have to sit at least that far away and face the speaker. The test procedure doesn't really change to accommodate.

In this case, if measuring the speaker using a full polar plot the "handedness" will force the listener into a very narrow position where the FR is most even, which points to a certain weakness in design. And of course will show up while auditioning just one speaker.

Is it the left or the right speaker shown? (they are obviously mirrored). Glad you can however read the text on the speaker - but that wasn't my question ; )

Further away from the speaker the more the testing room becomes involved right? And would the drivers sum on axis or would it be slightly off axis?

And if I understand correctly, the head in a vice analogy is what you are referring to, but once in the sweet spot (as measured on axis) the speaker will sound good right?


So, translating this good mono result into a successful stereo result would require further testing in stereo to work out toe-in etc needed to create a decent frequency response and timbre for the LP. And adjust for the narrow position / response directivity etc - which is only possible to resolve in stereo.

So mono get's us FR timbre and tonality, and now we have these clues, we then revert to stereo to further investigate and resolve.

 

[Todd74]

So if a manufacture thought they don't need to put a tweeter in a speaker and it should only play to 5 kHz, you would be assuming that is the right thing to do?

So no, we are not here to listen to manufacturer's aims unless they can show research that what they are doing is more correct than nearly 40 years of research into what is correct.

Really, that is what we do in this forum. We are guided by body of research. Anything else is back to random assumptions and unfounded ideas. There are a million of them when it comes to speakers. No way we should bend in the wind depending on its direction. Manufacturers need to demonstrate the efficacy of their approach with controlled listening tests. If none exists, then they are going to be subjected to science that is based on that.

To which I would respond- if the manufacturer has a specific sound signature, and a large enough following of people covet that signature to make the company profitable, then I’d say they’re doing it correctly. “One man’s preferred curve is another man’s headache”.

To me, more attention needs to be paid to context, but that’s probably a pretty tall order and would require a shit ton more work.

 

[Blumlein 88]

In the video the point is made that a speaker with poor frequency response sounds closer to "better" speakers in stereo than mono, therefore mono testing is better at judging speakers. That doesn't necessarily follow, as that speaker could actually have pretty good stereo imaging which overcomes its frequency response deficiencies enough to raise it's score.

Stereo imaging is quite important to how I judge a speaker, and the differences between speakers in imaging are not subtle to me. Some people may prefer a speaker which images well to one with flatter response that does not image well.

From the video: "...the brain gets so much enjoyment out of that spatial quality..." - exactly!

So what part of an uneven response on or off axis makes a speaker image better if it isn't good otherwise? Maybe it is so, I can imagine the possibility, but Harman hasn't run across such a thing, and I'm not aware of others in my own experience where it was true.

 

[richard12511]

So what part of an uneven response on or off axis makes a speaker image better if it isn't good otherwise?

Narrower dispersion, though it will come at the expense of perceived spaciousness. Or maybe I don't understand your question.

 

[Thunder22]

Second, you all are relying on my assessment of a speaker. Don't you want my assessment to be more accurate?

I Yes, 100% agree with mono testing; thank you. Question: who's relying on your assessments? Me? All of us? I enjoy the site, but honestly , with the amount of speakers/equipment available ,in comparison to what YOU have tested, are we all really relying on that .0001 of speakers/equipment?

 

[NTK]

I Yes, 100% agree with mono testing; thank you. Question: who's relying on your assessments? Me? All of us? I enjoy the site, but honestly , with the amount of speakers/equipment available ,in comparison to what YOU have tested, are we all really relying on that .0001 of speakers/equipment?

Eh.... Which other site has comprehensive measurements of over 100 different models of speakers?

 

[pozz]

Further away from the speaker the more the testing room becomes involved right? And would the drivers sum on axis or would it be slightly off axis?

And if I understand correctly, the head in a vice analogy is what you are referring to, but once in the sweet spot (as measured on axis) the speaker will sound good right?

So, translating this good mono result into a successful stereo result would require further testing in stereo to work out toe-in etc needed to create a decent frequency response and timbre for the LP. And adjust for the narrow position / response directivity etc - which is only possible to resolve in stereo.

So mono get's us FR timbre and tonality, and now we have these clues, we then revert to stereo to further investigate and resolve.

No idea if it was the left or the right. I think even if the manufacturer indicated the handedness (would "chirality" be the appropriate word to use here?), we would need measurements to show which angle provides the most even response. Trust but verify, after all.

Yeah, head in a vice thing is what I was talking about, though the uneven left/right radiation would have definite consequences for spatial qualities. I couldn't say what those would be in advance. Likely the biggest issue would be difficult setup.

The rest of the procedure is as you said, including the fact that the further away you sit, the more the room is involved. At this point, when you start building the stereo setup, you start judging the room/speaker/listener interaction rather than just speaker itself.

 

[MerlinGS]

Imaging was included as part of "Spatial Quality". Spacial Quality is essentially imaging and envelopment grouped together, which makes a lot of sense when usually you have to trade one for the other. The speaker with higher spatial quality is the speaker with the better balance of soundstage width and image precision/clarity. I like it better than having having three different categories.

That highlights the problem. By burying imaging within spatial quality then a sense of space can obscure the variable of imaging. They are not the same thing. I have dipole and omnipolar speakers, they provide a great sense of space, but their sense of imaging is poor when I compare them to my speakers with high CD. They each have their strengths and weaknesses. But a measure that highlights a sense of spatial quality rather than differentiating the categories would be biased in favor of the dipoles and omnipolars vs CD.

 

[PeteL]

Playback through speakers is artificial from the outset. Note that, in nature, it is impossible to have two of the same sounds coming from two different locations. But two channel stereo routinely plays sounds in just that manner to produce the phantom center. And on top of that takes all of the ambient directional reverberation information and confounds it to emanate from two frontal points.

What you are describing is not regular stereo, but binaural audio, which has to be individually tailored to a specific person with microphones at their eardrums (or synthesized as such), not any general collection of intensity/timing differences. True soundfield accuracy is found by using spatial sampling, which is reproduced in playback through wavefield synthesis systems, which aren't commercially available (they exist as research projects in certain universities).

Localization refers to your innate ability to perceive sounds in a space. The fact that the source is a single speaker does not in any way impede your ability to localize them to that speaker. If you are interested you can look up work on monaural vs. binaural localization. Your ability to perceive height for example is mostly monoaural.

You sure put a lot of tought into it, Yes I understand what is a binaural recording and no, it’s not what i’m reffering to. what are you trying to say, that the concept of stereo image and soundstage is nothing else than a myth? that the fact of panning an element does not move where it’s percieved as coming from? Of course I know the perception of height, or to some extent depth, has not much to do with having two speakers, but it’s not sufficient is it, you’re never gonna get wwidth in mono!

 

[maverickronin]

That’s not how science works, Speaker 3 here is a control.

The Quad is not a proper control for answering the question people are asking. The radiation pattern is far too different. This leaves multiple ways to interpret the data.

It is just as equally valid to interpret the data as showing that the narrower the directivity the more disadvantaged a speaker is in mono.

To find out which is correct we would need tests which held frequency response more or less constant and varied directivity.

The Harman/Toole research was mostly conducted with conventional forward firing hi-fi cone and dome speakers with broadly similar directivity patterns. You can't can just throw in a few omnis, panels, and/or narrow beamwidth horns and assume the same conclusions apply to them as well. It may or may not.

 

[Arc Acoustics]

If you had a loudspeaker that sounds "bad (I mean bad, not just less pleasant.)" in mono, that is definitely a bad loudspeaker, it's basically hopeless.
(Probably dedicated toe-in design does not matter other than mild tilting of frequency response because if you had that bad response in the frontal axis next to the "designed (or intended)" axis, it's a bad loudspeaker.)
But If you had a loudspeaker that sounds good in mono, that is not necessarily good enough in stereo (at least for me).
This is my humble simplest statement and the difficulty I currently have as a complete novice loudspeaker designer.

I did make "a" prototype just because it's a tight budget.
Obviously, the mono test does not reveal the stability or depth of the sound image, cos it's a phantom, fake thing, and I'm trying to make be a good faker.
My prototype sounds good enough in mono because I designed it to have a good measured performance and subjective impression in mono, I know how to do it, it's basically a piece of cake.
But I didn't design to have good characteristic in stereo because I just don't know the proper target.

So I still can't have absolute confidence in the stereo performance.
At the stereo performance, I'm completely relying on the measurement, comparison to very few well-designed monitors, and my intuition, luck, who knows.

 

[pozz]

You sure put a lot of tought into it, Yes I understand what is a binaural recording and no, it’s not what i’m reffering to. what are you trying to say, that the concept of stereo image and soundstage is nothing else than a myth? that the fact of panning an element does not move where it’s percieved as coming from?

You said:

I don’t disagree with testing in mono, but your rationale for doing so does not apply (nor make sense) In the “natural world” sound can come from anywhere, 360 degree x 360 degree. Listening in mono means not being able to localise the source in space. Stereo, along with various miking techniques and fx allows to create a space where you can localise various sources. It’s based on the fact that you have two ears. There is nothing natural to listen in mono.

I think there's a vocabulary difference here and maybe some misunderstanding of what mono, stereo and localization are.

The difference between stereo and mono is not necessarily two loudspeakers vs. one loudspeaker. Mono is produced in stereo circumstances when channels play the same signal simultaneously. That's what phantom center is: a mono signal. Stereo happens when there is any set of intensity or timing differences between channels. It does not have to refer to two channel audio either: 5.1 and 7.1 multichannel work on a stereo principle to shift sound from speaker to speaker (and there are other principles for multichannel; my favourite example is WFS).

What stereo produces does not match the natural circumstances of sound at all (think directivity of natural sound sources and instruments). So out goes your nature argument when talking about the merits of mono vs. stereo.

Localization in psychoacoustics refers to the ability to pinpoint direction and to some extent distance of sound sources. You can't turn this off. This is an innate ability, and it doesn't matter what you are hearing. If you are listening to one loudspeaker you will localize the sound coming out of it. What you were probably talking about is what most people would call imaging. Well, a single speaker produces images too. It's just that they are anchored to the speaker, not to a phantom reference point.

 

[pozz]

The Quad is not a proper control for answering the question people are asking. The radiation pattern is far too different. This leaves multiple ways to interpret the data.

It is just as equally valid to interpret the data as showing that the narrower the directivity the more disadvantaged a speaker is in mono.

To find out which is correct we would need tests which held frequency response more or less constant and varied directivity.

The Harman/Toole research was mostly conducted with conventional forward firing hi-fi cone and dome speakers with broadly similar directivity patterns. You can't can just throw in a few omnis, panels, and/or narrow beamwidth horns and assume the same conclusions apply to them as well. It may or may not.

Isn't it enough to rank tonal and spatial qualities separately?

 

[whazzup]

Are there any scientific reasons for it, though? Like, could these hidden defects be heard in certain material? The studies would have been much more useful by trying to ascertain this, instead of forgetting this "small" philosophical detail being that if you can't hear it it doesn't matter.

That seems to be the case for the Elac Uni-Fi 2.0 review, where Amir identified an issue (with an Eva Cassidy track) which many refuted, until Andrew Jones reproduced the issue, and finally JoeNTell retested and narrowed it to a 585hz resonance on his own unit.

 

[Coach_Kaarlo]

No idea if it was the left or the right. I think even if the manufacturer indicated the handedness (would "chirality" be the appropriate word to use here?), we would need measurements to show which angle provides the most even response. Trust but verify, after all.

Yeah, head in a vice thing is what I was talking about, though the uneven left/right radiation would have definite consequences for spatial qualities. I couldn't say what those would be in advance. Likely the biggest issue would be difficult setup.

The rest of the procedure is as you said, including the fact that the further away you sit, the more the room is involved. At this point, when you start building the stereo setup, you start judging the room/speaker/listener interaction rather than just speaker itself.

FYI Terminals are handed (inside corners of speakers), as are the speakers (marked left and right), and the manual even illustrates correct handedness. Right hand speaker has tweeter outset, mid driver inset, left speaker is opposite. Swapping them changes the image and space in stereo considerably.

Looking at the frequency response red has mid range driver closer to mic, blue has tweeter closer to mic. Measurements of the speaker were about 1,000mm away, and then about 600mm either side, with mic roughly the height of the tweeter.

So in mono, you can determine quite a lot of useful information, but not enough to understand the true performance of that speaker in a room in stereo.

FWIW - I have been listening to my F208's compared to these SX-1000 Labo's - in MONO. Definitely a useful way to experience the differences between speakers, but also incomplete and inconclusive until the next steps you describe are completed in stereo (room / speaker / listener etc).