Is Jay talking about Amir?

[redshift]

Let’s see if we can define the framework.

Multiple choice:
a. I came to this forum to complain about the quality of the measurements (i.e. I believe they are not accurate)
b. I came to this forum to complain about the quantity of the measurements (i.e. I believe they are not enough)
c. I came to this forum to complain about the rules of the forum
d. I came to this forum to complain because no other forum will accept me
e. I came to this forum to show off my technical background by belittling others (by the way many people in here could do this in their area of expertise, but choose not to)
f. I am from Finland, a superior country with superior engineers
g. I came to this forum to contribute to the scientific discussions about speaker measurements and help others make better choices.
h. None of the above.

Please select one. Thx.

A quiz; I love quizzes.

f. Of course.

Finnish engineers are superior. Take a normal human being, strip away all touchy feels and shove them through a STEM program. How could it possibly end in another way?

 

[Trell]

Ok, let’s give the audience some context to how things work in the eastern region of Scandinavia. Remember to not mention the Swedes and ice hockey.

(Runs for cover)

View attachment 141549

Finland is not part of Scandinavia but is one of the Nordic countries.

 

[redshift]

Finland is not part of Scandinavia but is one of the Nordic countries.

Damn right these Finns aren’t welcome in our club of mutual admiration in Scandinavia.

(I’m just verifying that you guys still are on the mark )

We mostly use Finns to keep those pesky Russkies and Poles at arms length distance when SHTF. (for the obvious reasons)

 

[amirm]

For a while I thought this is not North Korea where dictator decides what data people need to see and what is important or just interesting for them. But of course you have every right to keep others deaf, idiots or minors under your guardianship. I can't tolerate such arrogance so hopefully someone with moderator rights is able to erase me if you can't.

If you go to a restaurant and don't like the food, you leave. You don't shout profanity so they throw you and then you can cry victim and that they are the problem. You don't need any permission from anyone to stop posting.

Be here to constructively contribute to technical topics. Learn how to make persuasive technical arguments. Plenty of your peers here do that day in and day out. If you can't learn this, then that is the reason you are saying there is no forum for you. No one invites you to a party if all you are going to do is spit in the direction of the host and condemn the food.

 

[amirm]

You are talking about single wide band systems such as amplifiers. That kind of simplified assumption is not whole truth with multiway loudspeakers having both mechanical and acoustical links between different ways/bands.

We listen to the whole speaker which acts as a system. It cannot get past the basic mathematics that says the distortion it applies to one tone, is the same as it does to two tones. Mathematically you can drive the IMD from THD (with phase) of individual tones.

The thing IMD does which was useful in the days we did not have FFT and such, is that it simultaneously tests a device at a low and high frequency. With a single tone test we don't have this. So this is why it became popular. It is a myth that it produces new data. It cannot.

Already mentioned few mechanisms such as cone of conventional hifi coaxial (Kef, Seas etc) which acts like wave guide vibrator causing IMD products at HF. That is completely different than result of non-linearities of individual radiators, and can be higher and more audible than harmonics - especially in 2-way applications. PA coaxials usually have some kind of wave guide for tweeter which isolates wavefront of tweeter from vibrating cone so sound clarity could be significantöy better than with hifi coaxial.

Said with a wet thumb in the air to detect air temperature. You want to tell me what is audible, present psychoacoustic research or controlled listening tests. Don't tell me a perceptually blind test like IMD tells you this and that. It does not at all by itself. You have to decompose the problem, apply masking and threshold of hearing to arrive at possibility of audible problems. Here is an example for you:

SubwooferPerformancefor Accurate Reproduction of Music*
LOUIS D. FIELDER
Dolby Laboratories, /nc., San Francisco, CA 94103, USA
AND
ERIC M. BENJAMIN

On Audio Eng. Soc., Vol.36,No.6, 1988 June (peer reviewed paper):

Now this research was about IMD distortion of subwoofers not whole speaker. The point is to show you that there is a proper way to make an argument in the forum, and then there is the hand waiving one that says, "I know more than you so shut up and listen." That would be what N. Korea dictators might do.

Another already mentioned mechanism is pressure leak to rear side of the radiator. Leak biases operating point of the motor causing intermodulation products. This happens if designer assumes that tweeter is sealed while it's actually not (enough). This is not all.
Measurement as harmonics is also limited to bandwidth of output port/stage so you cannot measure non-linearities as harmonics in acoustical domain above ca. cone break-up freq. / 2 without multi-tone.

You are talking about old measurement systems. We can measure harmonic distortion well past the audible limit with high sample rate ADC. And indeed I do this now. It is not needed in real life though as the energy at 20 kHz is so low in music that what intermodulation or harmonic distortion it generates is of no value. Test tones are run at full amplitude which is not at all representative of what happens in reality. We keep the volume down in these tests or we would instantly blow up the tweeter! Such of course doesn't happen with real music.

Let me finish by saying any measurement has value if you are designing something and are chasing a specific problem. Indeed often you create custom measurements for certain problem. In that regard, if you are troubleshooting some problem like you mention, maybe IMD output is more intuitive to you than THD graph. Indeed, the "ESS DAC IMD Hum" problem I found with DACs was far more easily visible in IMD graph. Later however, I managed to show the same with THD although it took some work. So I am not dismissive of these tests in general but rather, in the context of doing a review and measurements being compared across a range of speakers.

I actually tried to quantify the IMD "problem" with coaxial drivers but could not. Whether it was due to large variations between coaxial speaker and another, noise, etc., it simply did not turn out that the measurements showed a problem there. Even if it had, then the next challenge would have been to show audibility of such which would be super challenging.

As you see, the complexity of the topic is fully understood. Your view is simply too myopic to have value in the context of what we do here.

 

[amirm]

S&R posts the FR for comparison and measure the difference; basically measuring in %. I

??? This is an example from their latest test: https://www.soundandrecording.de/equipment/psi-audio-a14-ms3-nahfeldmonitor-im-test/

The amplitudes of the multitone are clearly modulated by the frequency response of the speaker. Where are you seeing the normalization or percentage?

 

[q3cpma]

??? This is an example from their latest test: https://www.soundandrecording.de/equipment/psi-audio-a14-ms3-nahfeldmonitor-im-test/

View attachment 141669

The amplitudes of the multitone are clearly modulated by the frequency response of the speaker.

Huh? Where? Or you just mean that the distortion level tracks the output level? That's quite logical, and the signal is supposed to represent typical music.

Where are you seeing the normalization or percentage?

Basically, they display the red curve as "what you're actually getting" as opposed to the input signal (green). You can then "measure" the distance between blue and red. I didn't communicate this very well, though.
You could limit this to mostly flat speakers, too; kind of a "bonus" measurement for stuff that has already low linear distortion.

Anyway, this exchange just helps my point: it (just) needs discussion.

 

[amirm]

A bit like the CSD spectrogram, where S&R's is very useful because it uses the same scales every time.

I use the same scale all the time now and have been for quite a while. CSD as I have explained many times either only tells you what you already know from other measurements, or spits out information because of the way it is run. I have yet to see it add much value to the assessment of the speaker.

I suggest reading Dr. Toole's writing in this regard from his book:

You know it is trivial for me to post CSD graphs. I run it for every speaker by the way even though I don't post it. Putting it in the review will surely make it look for technical and fancy. But I resist that temptation because it not only doesn't add value, it can subtract.

As I said for IMD, CSD can have uses in chasing specific problem. But in the context of filtering out what is or is not a good speaker, in 99% of the cases it does not do that.

Here is Dr. Toole again:

 

[q3cpma]

I use the same scale all the time now and have been for quite a while. CSD as I have explained many times either only tells you what you already know from other measurements, or spits out information because of the way it is run. I have yet to see it add much value to the assessment of the speaker.

I suggest reading Dr. Toole's writing in this regard from his book:

View attachment 141670

You know it is trivial for me to post CSD graphs. I run it for every speaker by the way even though I don't post it. Putting it in the review will surely make it look for technical and fancy. But I resist that temptation because it not only doesn't add value, it can subtract.

As I said for IMD, CSD can have uses in chasing specific problem. But in the context of filtering out what is or is not a good speaker, in 99% of the cases it does not do that.

Here is Dr. Toole again:

View attachment 141671

I completely agree with you that we have no psychoacoustic facts of worth to analyze thel. But it's still very interesting when you can see some strange behaviours like with the Ones.

But this is really "no data", which isn't the same as "data that proves that it doesn't matter", as this Olive paper reports.

 

[amirm]

Anyway, this exchange just helps my point: it (just) needs discussion.

But it doesn't. These are all perceptually blind measurements. Having one or two as I post for good measure is fine. But loading up the review with tons of graphs, none of which tell you visually what the audible problem is, is not good. Once you consider that people will only tolerate looking at a handful or measurements before moving on and you see why I am loathe to add to the list.

The current THD comparison at a glance tells you how uncomfortable a speaker is getting:

Beyond that, we would just be measureabating and that is something I don't want to do.

Yes, I realize a tiny percentage of you want all the measurements in the world. You will read and examine them all and maybe get more insight. I am just not your man for that. I get challenged on everything I post and *I* have to defend them. I can defend the above graph. I can't defend that convoluted measurement from S&R. 10% THD? Crest factor? What the heck???

 

[q3cpma]

But it doesn't. These are all perceptually blind measurements. Having one or two as I post for good measure is fine. But loading up the review with tons of graphs, none of which tell you visually what the audible problem is, is not good. Once you consider that people will only tolerate looking at a handful or measurements before moving on and you see why I am loathe to add to the list.

The current THD comparison at a glance tells you how uncomfortable a speaker is getting:

Neumann showed with a KH120A/KH310A comparison that you cannot rely on THD only.

Beyond that, we would just be measureabating and that is something I don't want to do.

Yes, I realize a tiny percentage of you want all the measurements in the world. You will read and examine them all and maybe get more insight. I am just not your man for that. I get challenged on everything I post and *I* have to defend them. I can defend the above graph. I can't defend that convoluted measurement from S&R. 10% THD? Crest factor? What the heck???

I respect your position, honestly, but my view is that you're doing a very important work and won't measure the same speaker again (except for degenerate cases), so getting all the necessary information the first time could be very important. Now that I'm thinking about it, doesn't the Klippel already store phase information, anyway? It must have it, at some point, no?

About IMD, the "more ways and lower driver excursion better" rule of thumb should be enough for most cases, but there are some surprises, sometimes (cf Focal Trio11 by S&R, quite high IMD compared to Genelec/Neumann). In the end, it's just beggars trying to choose, so don't mind us.

(and if I were to play the "avocat du diable" for you, I'd say that using SINAD, an unweighted metric, instead of just showing the FFT might have very low psychoacoustic value too; if only AP and Klippel did implement Geddes' metric)

 

[Sal1950]

I will save you watching the whole video, at the end he says the measurements (of a speaker) that matter are done with a tape measure. Use it to measure the distance to each speaker and there you have it! Incredible....

Thanks, I've wasted more that enough time in my life on airheads like this.

 

[dfuller]

About IMD, I don't even care about its measurement, since I don't need more than "2-ways are worse than 3-ways, even at similar THD levels" (even if S&R shows some suprises, sometimes, like the Focal Trio11 which has quite high IMD compared to the 8361A or KH420A). In the end, it's just beggars trying to choose, so don't mind us.

What I find particularly interesting about the Trio11 is that it's got very low harmonic distortion, much lower than the KH420s especially in the bass region, but the IMD is relatively high. That said the tests don't entirely seem to match. The Trio is at 123dB SPL peak at 1m, the KH420 is 101dB SPL peak at 4m. Evening that out, that's 110dB SPL at 4m for the Trio. So yeah, of course it's higher distortion - it's tested at a way higher volume.

 

[q3cpma]

What I find particularly interesting about the Trio11 is that it's very low harmonic distortion, much lower than the KH420s especially in the bass region

Not really. The Trio11 is only better under 100 Hz, otherwise it's very inferior (max ~10 dB difference) in the MF and slightly inferior in the HF (with a distortion peak from Focal at 5 kHz). What's too bad is that we only get THD from S&R, and not detailed components like Amir shows.

but the IMD is relatively high. That said the tests don't entirely seem to match. The Trio is at 123dB SPL peak at 1m, the KH420 is 101dB SPL peak at 4m. Evening that out, that's 110dB SPL at 4m for the Trio. So yeah, of course it's higher distortion - it's tested at a way higher volume.

Indeed, I was (implicitely) talking more about the spectrum than level. For me, a 3-way speaker shouldn't have as much IMD after 1 kHz (because sensitivity is greater here).
Always found it strange that they measure at different levels everytime; they should just do 85 dB SPL average at the listening position with 1 m for nearfield speakers, 2 for midfield and 3 or 4 for farfield.

 

[Blaspheme]

But it doesn't. These are all perceptually blind measurements. Having one or two as I post for good measure is fine. But loading up the review with tons of graphs, none of which tell you visually what the audible problem is, is not good. Once you consider that people will only tolerate looking at a handful or measurements before moving on and you see why I am loathe to add to the list.

The current THD comparison at a glance tells you how uncomfortable a speaker is getting:

Beyond that, we would just be measureabating and that is something I don't want to do.

Yes, I realize a tiny percentage of you want all the measurements in the world. You will read and examine them all and maybe get more insight. I am just not your man for that. I get challenged on everything I post and *I* have to defend them. I can defend the above graph. I can't defend that convoluted measurement from S&R. 10% THD? Crest factor? What the heck???

The graphs depicted in this post are pretty ordinary, as we've discussed, so doing more like that won't help much. Your waterfalls also. When you get better at visualisation, maybe. Have you read Tufte?

 

[Blaspheme]

If you go to a restaurant and don't like the food, you leave. You don't shout profanity so they throw you and then you can cry victim and that they are the problem. ....

The restaurant analogy is weak. These wide-ranging forums are more like a smorgasbord where everyone is encouraged to bring their own to share.

 

[Trell]

The restaurant analogy is weak. These wide-ranging forums are more like a smorgasbord where everyone is encouraged to bring their own to share.

Sorry, resistance is futile!

 

[Wes]

The restaurant analogy is weak. These wide-ranging forums are more like a smorgasbord where everyone is encouraged to bring their own to share.

smorgasbord?? more pro-Swede an anti-Finn comments eh?

 

[Trell]

smorgasbord?? more pro-Swede an anti-Finn comments eh?

I dunno, but to Swedes Norway and Finland have only temporary escaped them, but they'll come back some day and own us! Or not So Swedes "think" they've invented everything, or something to that effect. The realities is that once upon a time Norway offered the Swedes 10% of the North Sea oil and gas for 10% in Volvo, but in the end the deal was broken by the Swedes. Thankfully! Dumb Swedes

 

[Jim Shaw]

If he is talking about me, he has no idea who I am . At one point he says to ignore a guy who measures speakers in his room at 1 meter. Well, that ain't me.

I will save you watching the whole video, at the end he says the measurements (of a speaker) that matter are done with a tape measure. Use it to measure the distance to each speaker and there you have it! Incredible....

I tuned out Jay after he once compared 2 amplifiers' outputs according to the volume knob setting. Sort of -- this one is louder at volume 3 than that one at 7. At the time, I estimated he couldn't quality as a Best Buy salesman. Or, maybe he could....

Some of these guys are like country preachers: they don't want any smart folk in the pews.