THD has a much bigger effect on sound than you think

[peng]

I am talking about "cumulative" bass distortions. Not a single tone distortion. For example, add all distortions from the bass notes, for example 20 to 200 hz,

I am not sure what you meant by "cumulative" bass distortions. THD is already the "cumulative" in a sense, so if at 1000 Hz, THD is 0.005%, that 0.005% would represent all of the harmonic distortions, i.e. 1000,2000,3000,4000,5000,6000,7000,8000,9,000,10,000...........................20,000 Hz and higher.. When you say "for example 20 to 200 Hz", that really doesn't apply to amplifiers because the amplifier will see whatever voltage is applied to its input at any particular instant and amplifies it. The signal may represent many tones but to the amplifier it still one varying voltage, one value at a time, and the total harmonic distortions in dB or % represents the distortions reference to the magnitude of the fundamental frequency, one frequency at a time, not over a range of frequency. THD 0.08%, 20 to 20,000 Hz simply means THD over the 20 to 20 kHz range does not exceed 0.08%. I am sure you know that but again I just want to understand more clearly what do you mean by "add all distortions from the bass notes, for example 20 to 200 hz". May be you can clarify it with a numerical example?

If you look at the FFT of the AVR-X3700H to see the individual harmonic distortion instead of the "Total/cummulative" harmonic distortions, the 2nd harmonics + noise was the highest but still only -95 dB vs the Total harmonics distortion plus noise of about 88 dB if you plug that into solderdude's calculations you will see that it would hardly be a factor. As he said, in his example he picked the amp with the worst THD+N on the ASR chart.

 

[mike7877]

OP here, it occurred to me we need to take into account the average to peak level (crest factor) of music - pop/rock etc. Which is 10-20db in modern music.

It makes sense to subtract 15db from the level you're measuring from for masking.

Edit: I'm pretty sure I can hear my furnace at less than 30db running when I've got music on at 105db, so this -50db threshold thing makes no sense to me

People seem to be forgetting that the treble is 20-30db lower in level than the bass/mid bass most of the time, sometimes with periods of silence in between. It's that level which you use to subtract from, not the bass (you hear through the bass). If the harmonic is at -50db and the treble is at -30db? 20db difference. If it's during a break? It's all there is.

 

[solderdude]

I'm pretty sure I can hear my furnace at less than 30db running when I've got music on at 100db (LOUD)

That's logical because there is no relation to the music. When you add 30dB of noise into a mix which has music with peaks of 100dB and average levels of 85dB then non correlated sounds like the noise (which is in many frequency bands) is merely 55dB difference which you can hear because they are not related.
However, when you have harmonics that are down 55dB which are related to the music you can't hear them.

So yes, of course you can hear sounds that low because they are constant and wide band and not related to the signals.
This is noise and not distortion.

 

[mike7877]

That's logical because there is no relation to the music. When you add 30dB of noise into a mix which has music with peaks of 100dB and average levels of 85dB then non correlated sounds like the noise (which is in many frequency bands) is merely 55dB difference which you can hear because they are not related.
However, when you have harmonics that are down 55dB which are related to the music you can't hear them.

So yes, of course you can hear sounds that low because they are constant and wide band and not related to the signals.
This is noise and not distortion.

Third harmonic is NOT (!) related to the music. It is like a wrong note. It is a clash, more intrusive than white noise. It isn't generally heard as a tone, it's just present and interferes with your ability to hear detail of the actual signal - it makes things less clear. Like having people talking around you while you're trying to talk to someone

 

[peng]

Golden ears should get their hearing checked here regularly.

Distortion Listening Test

Ran into this interesting listening test by Klippel with regards to how much distortion you can hear. This is the link: http://www.klippel.de/listeningtest/lt/ Just casually wanting to see the test, I went with the defaults and for some reason, the levels were exceptionally low. I had to set...

www.audiosciencereview.com

Or Archimago's.

INTERNET BLIND TEST: Is high Harmonic Distortion in music audible? (plus Pet Shop Boys' newest, HRA needs HDR)

A blog for audiophiles about more objective topics. Measurements of audio gear. Reasonable, realistic, no snakeoil assessment of sound, and equipment.

archimago.blogspot.com

 

[Pdxwayne]

I am not sure what you meant by "cumulative" bass distortions. THD is already the "cumulative" in a sense, so if at 1000 Hz, THD is 0.005%, that 0.005% would represent all of the harmonic distortions, i.e. 1000,2000,3000,4000,5000,6000,7000,8000,9,000,10,000...........................20,000 Hz and higher.. When you say "for example 20 to 200 Hz", that really doesn't apply to amplifiers because the amplifier will see whatever voltage is applied to its input at any particular instant and amplifies it. The signal may represent many tones but to the amplifier it still one varying voltage, one value at a time, and the total harmonic distortions in dB or % represents the distortions reference to the magnitude of the fundamental frequency, one frequency at a time, not over a range of frequency. THD 0.08%, 20 to 20,000 Hz simply means THD over the 20 to 20 kHz range does not exceed 0.08%. I am sure you know that but again I just want to understand more clearly what do you mean by "add all distortions from the bass notes, for example 20 to 200 hz". May be you can clarify it with a numerical example?

If you look at the FFT of the AVR-X3700H to see the individual harmonic distortion instead of the "Total/cummulative" harmonic distortions, the 2nd harmonics + noise was the highest but still only -95 dB vs the Total harmonics distortion plus noise of about 88 dB if you plug that into solderdude's calculations you will see that it would hardly be a factor. As he said, in his example he picked the amp with the worst THD+N on the ASR chart.

So, in that worse case amp, the multitones test basically telling us the harmonics added to all freq is at about -50db?

 

[solderdude]

Third harmonic is NOT (!) related to the music. It is like a wrong note. It is a clash, more intrusive than white noise. It isn't generally heard as a tone, it's just present and interferes with your ability to hear detail of the actual signal - it makes things less clear. Like having people talking around you while you're trying to talk to someone

O.K. so the guitar note in the following plot does NOT have odd harmonics and just even ones ?

 

[mike7877]

O.K. so the guitar note in the following plot does NOT have odd harmonics and just even ones ?
View attachment 160793

That's all chopped up! I'm sure there's some third harmonic present, but it's not dominant. There seems to be a lot of HF energy with one root note

Point is, more often than not. Actually, most often not, the third harmonic is out of place if artificially introduced after the fact

 

[solderdude]

So, in that worse case amp, the multitones test basically telling us the harmonics added to all freq is at about -50db?

View attachment 160792

You are misinterpreting this plot.
1: The frequencies you see are all the same amplitude which won't be the case with music.
2: The actual signal is near 0dB which won't be the case with music.
3: You see harmonics + IM products of all frequencies at high amplitudes which won't be the case with music as amplitudes vary and some of the grass will be masked and lower in reality.

 

[mike7877]

So, in that worse case amp, the multitones test basically telling us the harmonics added to all freq is at about -50db?

View attachment 160792

Those are all the harmonics of the multiple tones. It gets thicker at the top because there are more root notes earlier (lower)

 

[solderdude]

That's all chopped up! I'm sure there's some third harmonic present, but it's not dominant. There seems to be a lot of HF energy with one root note

Point is, more often than not. Actually, most often not, the third harmonic is out of place if artificially introduced after the fact

What does dominant have to do with it. In the worst case amp 3rd harm distortion of the amp generated by the fundamental will be much lower than the one from the guitar. It will be masked and even when it would be slightly higher it would barely change the sound of the tone.

 

[mike7877]

What does dominant have to do with it. In the worst case amp 3rd harm distortion of the amp generated by the fundamental will be much lower than the one from the guitar. It will be masked and even when it would be slightly higher it would barely change the sound of the tone.

The 250hz snare up at -3db introducing harmonics around 1-2khz (speech intelligibility range) is more what we're talking about. Don't accidentally confuse the issue!


See my post #102 and address what's there, no point talking if youre not taking what I said there into account

 

[solderdude]

Here's another one for you:

As you can see the oboe and clarinet have 3rd harmonics higher than the fundamental. It's why it sounds different from other instruments.
In case of the oboe harmonics are high even up to the 8th harmonic where in 'audiophool' amps their Harmonics usually only go as high up as 4th or 5th and then are below noise levels.

 

[mike7877]

Here's another one for you:

View attachment 160796

As you can see the oboe has 3rd harmonics higher than the fundamental. It's why it sounds different from other instruments.

The 250hz snare up at -3db introducing harmonics around 1-2khz (speech intelligibility range) is more what we're talking about. Don't accidentally confuse the issue

See my post #102 and address what's there, no point talking if youre not taking what I said there into account

The oboe's 4th harmonic is dominant, not third. An even harmonic

 

[solderdude]

it was addressed in post # 103

 

[solderdude]

The oboe's 4th harmonic is dominant, not third. An even harmonic

I said the 3rd harm is higher than the fundamental. I did not say it was the highest in amplitude nor used the word dominant. You claim 3rd harmonics sound bad. In that case the oboe and clarinet sound bad as well as they have lots of harmonics incl. odd ones.
Don't accidentally or purposely confuse the issue

 

[mike7877]

It occurred to me we need to take into account the average to peak level (crest factor) of music - pop/rock etc. Which is 10-20db in modern music

People seem to be forgetting that the treble is 20-30db lower in level than the bass/mid bass most of the time, sometimes with periods of silence in between. It's that level which you use to subtract from, not the bass (you hear through the bass). If the harmonic is at -50db and the treble is at -30db? 20db difference. If it's during a break? It's all there is.




So, subtract 15db for the crest factor and 20-30db for treble being that much quieter. You're at -35 to -45db now. If harmonic distortion is at -60, it's 15-25db down. Audible, easily audible

 

[Pdxwayne]

You are misinterpreting this plot.
1: The frequencies you see are all the same amplitude which won't be the case with music.
2: The actual signal is near 0dB which won't be the case with music.
3: You see harmonics + IM products of all frequencies at high amplitudes which won't be the case with music as amplitudes vary and some of the grass will be masked and lower in reality.

It is for 5 watts.....

 

[Killingbeans]

Again, I am talking about overall. All the distortions from bass regions should be able to increase the sense of treble by 2db?

I think I get what you're trying to say. But the thing is, you would only get an increase in amplitude in the frequencies where the harmonics exactly overlap? And even then it's not: Distortion1 + Distortion2 = DistortionTotal, it's: SQRT(Distortion1^2 + Distortion2^2) = DistortionTotal. Meaning that the biggest contributor will by far be the dominating one. You would need a crapload of distortion over a wide frequency range to get anywhere remotely close to a 2dB increase?

 

[mike7877]

I said the 3rd harm is higher than the fundamental. I did not say it was the highest in amplitude nor use the word dominant. You claim 3rd harmonics sound bad. In that case the oboe and clarinet sound bad as well as they have lots of harmonics incl. odd ones.
Don't accidentally or purposely confuse the issue

If it's part of the instrument, fine, it's adding to its character.
If you change the amount (add to or subtract) some of the harmonics, the instruments no longer sound natural. This is one reason why you can't tell if something is real or synthesized with cheap stereos with higher THD. eg trumpet


You still haven't addressed what I've said twice now...