Audibility of nonlinear distortion

[Pan]

If we could see the spectrum of the distortion from the test, then we would most probably see strong 2nd and 3rd harmonic which should be relevant to most loudspeakers.

Either I get it wrong or there IS a strong corellation between THD and listening experience, if you take into account that this THD figure is dominated by 2nd and 3rd harmonic THD is about the simplest number that can let us compare two loudspeakers. I do not believe that there are many woofers with higher order harmonics in the distortion. 1 % THD is -20 dB, 0.1 % THD is -40 dB, right? I could easily hear -30 dB THD with their model speaker - and I would bet it was mostly 2nd and 3rd harmonic. Nobody in the world can persuade me that distortion does not matter.

Or the test is not relevant and contains more higher order harmonics

1% is -40dB
0.1% -60dB

Please note that the figures that we scored are not absolute levels, it's the loudpseaker distortion SUBTRACTED with the dB reading. That means that if the speaker has 1% dist (of whatever type) than if you scored -30dB it means that this specific dist needs to be lowered down from-40dB (which is the same as 1%) to -70dB. Few speakers has that good performance.

The readings would likely be different if the same driver was high passed to a decent 12" woofer though but the test still shows that nonlinear distortion is a real problem.



/Peter

 

[Pan]

I agree - THD can be measured (AFAIK) with just a sinewave at a certain level - but I think a series of measurements like this can give a hint about total distortion performance / nonlinearity. You can see what I mean for example in this datasheet: http://www.seleniumloudspeakers.com/site2004/catalogo/pdf/12W10P.pdf

Exactly! THD numbers plotted as a graph thru the whole audio band or from low to higher amplitudes tells a lot about the device behaviour.

You are right about IMD - with two tones, I could easily hear the modulation products (kind of a tremolo effect). Guitarist use this to tune a guitar - you play the same harmonic on two strings - the faster the sound pulsates, the more the strings are out of tune.

What we hear is both the beating from the two tones but also teh IMD products. I play the guitar btw.

By the way, have you noticed that in the octave and two tone test the distorted one seems as it is "out of tune", a bit lower than the other?

Yes, there are many such phenomena going on. Pitch changes with spectral content and also with amplitude. Therefore small amounts of distortion can have strange effects on most every audible parameter on the audio passing thru a nonlinear device.


/Peter

 

[poptart]

Pan,

So are you saying there could not be a case where one speaker sounds less distorted than another even though it has a higher THD measurement? I can't point to a pair of speakers that meets these criteria offhand, but it seems to me that this would be possible. This is all I meant by my post about THD, even in a simplified case like this where only low order distortion is produced looking at THD numbers still might not tell us which speaker sounds better.

Also I play the guitar and while the analogy to tuning may help describe beat frequencies to some people I need to point out you can't actually tun a guitar with this method. People try, I know, but the pitches produced when you play those harmonics are not the correct ones for an even tempered scale.

 

[jcx]

there may be unintentional "clues" in some of Klippel test files:

http://www.diyaudio.com/forums/showthread.php?postid=1413127#post1413127

have these problems been fixed and the statistics reset?

bimodal results with a peak at the test floor likely points to test implementation errors

 

[Pan]

Pan,

So are you saying there could not be a case where one speaker sounds less distorted than another even though it has a higher THD measurement?

The sounds (as we all know) depends on many things for ex. both linear and nonlinear distortion and I wouldn't say it's impossible but IMO not very likely either. Speakers that are improved for example with copper in the gap tend to sounds better as HD+IMD are decreased with the decreased inductance.

I can't point to a pair of speakers that meets these criteria offhand, but it seems to me that this would be possible. This is all I meant by my post about THD, even in a simplified case like this where only low order distortion is produced looking at THD numbers still might not tell us which speaker sounds better.

Looking at THD graphs at various levels might tell us a whole lot of the audible performance IMO/IME.

Also I play the guitar and while the analogy to tuning may help describe beat frequencies to some people I need to point out you can't actually tun a guitar with this method. People try, I know, but the pitches produced when you play those harmonics are not the correct ones for an even tempered scale.

I suggest a new thread about guitar tuning. That said it depends on but I usually tune each string against the high E.


/Peter

 

[Pan]

have these problems been fixed and the statistics reset?

bimodal results with a peak at the test floor likely points to test implementation errors

I did not hear any clues in any of the tests files.. well other than the distortion of course.

The statistics looked a little funny, I agree.

Guess I have to apologize to the board for not running a search on this one, didn't know that a thread allready did exist on the Klippel test.


/Peter

 

[poptart]

I don't think we need a thread for the guitar tuning, it's a fact that dividing an octave into 12 equal sized steps as we have done in western music means we no longer have simple integer ratios for things like thirds, fourths and fifths. Look up the difference between just and equal temperament if you have doubts. The harmonics maintain the simple integer relationships of vibrating strings and just intonation, the frets do not. They are not supposed to match. The only exception is using an octave harmonic on a low string to compare to the same note on a high string.

 

[Pan]

Pan,

So are you saying there could not be a case where one speaker sounds less distorted than another even though it has a higher THD measurement?

The sounds (as we all know) depends on many things for ex. both linear and nonlinear distortion and I wouldn't say it's impossible but IMO not very likely either. Speakers that are improved for example with copper in the gap tend to sounds better as HD+IMD are decreased with the decreased inductance.

I can't point to a pair of speakers that meets these criteria offhand, but it seems to me that this would be possible. This is all I meant by my post about THD, even in a simplified case like this where only low order distortion is produced looking at THD numbers still might not tell us which speaker sounds better.

Looking at THD graphs

 

[pelanj]

Poptart, technically speaking, you can never tune a guitar right, even if the octaves are in tune (change in pitch with fretting the string due to lenghtening the string, etc.). Most of the time I just use a tuner, but these harmonics work wery well with distortion for a quick check, thats why I use them time from time.

Peter, 1 % is -40 dB, of course! (my fault ) Relative to 100 %. It was already too late I know the levels are relative to the tested woofer, we have quite similar results and the comment you made in one of the first posts applies to me too.

 

[Pan]

poptart,

I see you assume that I have not studied music theory which is wrong.

Check link for one solution to the "impferfect" standard guitar neck; http://www.truetemperament.com/site/index.php

Again I suggest a new thread for that or leave it here. Guitar tuning is a big and complex matter.


/Peter

 

[Pan]

The sounds (as we all know) depends on many things for ex. both linear and nonlinear distortion and I wouldn't say it's impossible but IMO not very likely either. Speakers that are improved for example with copper in the gap tend to sounds better as HD+IMD are decreased with the decreased inductance.



Looking at THD graphs

Some text dissapeared in cyberspace it seems.

What I think I wrote was:

Looking at THD vs frequency graphs at different levels and also THD vs level is useful and tells a lot about performance.


/Peter

 

[poptart]

it's not complex it's extremely simple. We dont't need some new tuning system either, equal temperament is the correct way to build a fret board just as it is the correct way to tune a piano.

Pelanj, use the harmonics method to "check" two strings are in tune. Now check with an electronic tuner. If you eliminated the beats between those harmonics the higher string is now several cents flat. Those two harmonics are supposed to beat a little when the strings are tuned correctly, that's the point. It's not a mistake or something that needs fixing, it's the difference between equal and just temperament. You will only prove you have not bothered to educate yourself on the difference between the two by denying this.

 

[Pan]

Please stop it. I know all of that and you are assuming things without any basis. I have ten guitars and I have played for 15-20 years, I have worked and modified my guitars + built other instruments from scratch.

I repeat myself, I do not wish this thread to be about guitar tuning which is a big and complex thing. If you can not accept this I will ask the moderators to lock this thread.


/Peter

 

[jeroen_d]

This was my result for the first test. You can imagine that I always have felt that non-lineair distortion in drivers is very important.

However, I have never heard a real driver sound so dreadfully distorted as the 'real' 6.5" driver used in this test. So I find the test of limited value. I'd rather see this test based on a nice modern driver with max 1% K2 and max 0.3% K3 harmonic distortion.

 

[Pan]

Perhaps we can get some info from Klippel about the driver used for modeling the test and also at which levels. Maybe that can add to the value of this thread/discussion.

I have done blind bypass tests on class A amps with about 0.5%THD at 1W and found them to be easily picked out as coloring the music. Class A topologies have some similarities to speaker distortion.


/Peter

 

[poptart]

You must have the last word on the subject or the thread gets locked huh? It's a basic technical discussion not a religious debate, relax. I too have been playing for more than fifteen years and do all my own work on my guitars and build my own amps but none of that expertise is needed, even a non guitar player can spend five minutes researching this and learn the truth. Also the simple experiment I described in my last post can be done by anyone with a guitar and a tuner and they will instantly see the harmonic method does not work. But since you seem dead set on proving it does, here you go, educate us mere mortals guitar wizard: http://www.diyaudio.com/forums/showthread.php?s=&threadid=134307

 

[Pan]

You must have the last word on the subject or the thread gets locked huh?

Absolutely not BUT it is common manners on the internet to respect the thread starters wish. I don't wish to talk about western music scales in this thread and I can not understand why you have such a hard time understanding that. Im not fanatic about staying on topic and often sway away myself, but can you please read what I write and try to understand it without inserting things that only exists in your imagination and not in the real world or in this thread?

It's a basic technical discussion not a religious debate, relax. I too have been playing for more than fifteen years and do all my own work on my guitars and build my own amps but none of that expertise is needed,

Of course not.. but perhaps someone in that position do know something about instruments right? Something you assume I did not (and still does for some unknown reason).

Also the simple experiment I described in my last post can be done by anyone with a guitar and a tuner and they will instantly see the harmonic method does not work.

And even though you state the above, you believe I'm clueless about it after decades of playing? Wow, what a compliment on my intelligence.. *LOL*

But since you seem dead set on proving it does, here you go,

Oh my you need to wake up, I NEVER SAID ANYTHING ABOUT IT!!

You really need to think more and write less. Get into the game will you!

And I try once more.. if you wish to discuss music scales and guitar tuning, start a thread becasue I do not wish to have it here!!


/Peter

 

[poptart]

I did start the thread you asked for. And where did I insult your intelligence or experience? I posted a one sentence comment containing a simple fact. You dispute this fact and in my opinion quite arrogantly claim to know more about the subject than anyone else. If you know something that contradicts hundreds of years of debate about equal temperament then by all means post it, but please stop acting like you are being assaulted simply because someone disagrees with you on a technical, non-emotional point. We're all adults here, we can disagree without needing to call the judge.