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Audible results from measurements
Yahzi
post Feb 23 2013, 06:08
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Hi there,

The claims I hear for audible differences existing for different electronics amount to frequency response, noise and distortion.

These distortion graphs are between the two I/V stages of a DAC :



And :



The claim is that these DACs measure flat, but the measurements show the effects of certain filters at play. Looking at the distortion components, is this enough of a difference to cause gross audible differences? The claims I hear are that different filters used in DAC design can result in audible differences irrespective if that DAC measured perfectly flat.

What do you think?
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splice
post Feb 23 2013, 13:11
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QUOTE (Yahzi @ Feb 22 2013, 21:08) *
... the claim is that these DACs measure flat, but the measurements show the effects of certain filters at play. Looking at the distortion components, is this enough of a difference to cause gross audible differences? The claims I hear are that different filters used in DAC design can result in audible differences irrespective if that DAC measured perfectly flat.

What do you think?



It is definitely not "enough of a difference to cause gross audible differences". Any amplifier manufacturer with aspirations to audiophile quality would be very pleased to attain such low THD+noise figures - in other words, the amplifier you play these DACs through will likely sound worse than the DACs.


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Yahzi
post Feb 23 2013, 14:09
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QUOTE ("splice")
It is definitely not "enough of a difference to cause gross audible differences".


What makes you think this?

This post has been edited by Yahzi: Feb 23 2013, 14:09
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DonP
post Feb 23 2013, 16:31
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QUOTE (Yahzi @ Feb 23 2013, 08:09) *
QUOTE ("splice")
It is definitely not "enough of a difference to cause gross audible differences".


What makes you think this?


How about that the biggest harmonic is 100 dB less than the primary signal?

Even if you filtered out the 1 khz signal, you wouldn't be able to hear the distortion unless you are gaming the volume control.
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Yahzi
post Feb 23 2013, 16:42
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I was having a debate with a DAC designer who cited these graphs as reasons for his sonic preferences, especially the first graph. He claimed that the harmonic distortion was the reason why he preferred the sound. But you are saying that the harmonic components are so far down, 100 dB's down and therefore inaudible.

Here are the impulse response graphs, respectively :



and :



Is this an example of a false positive result?

This post has been edited by Yahzi: Feb 23 2013, 16:54
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Wombat
post Feb 23 2013, 17:29
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QUOTE (Yahzi @ Feb 23 2013, 17:42) *
Is this an example of a false positive result?

What result? I see 2 pics with different post and pre-ringing. This proofs nothing for real audibility with a correctly working DAC. You also may try to visualize at what frequencies this ringing happens.
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Yahzi
post Feb 23 2013, 17:42
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The claim is that the harmonic distortion components in the first graph match the sonic preference of the lister .. the claim is that the added distortion makes things sound "nicer". His claim is that science agrees with his claim, because harmonic distortion makes things sound "nice".

If you saying that because the harmonic components are 100 dB down which no human could possibly perceive under any circumstances then the audible experience was based on a false positive result or conclusion. Correct?

Just wanted to ask : can different filters possibly affect sound staging or timbre? Or are those qualities determined by other metrics?

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julf
post Feb 23 2013, 18:09
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QUOTE (Yahzi @ Feb 23 2013, 17:42) *
If you saying that because the harmonic components are 100 dB down which no human could possibly perceive under any circumstances then the audible experience was based on a false positive result or conclusion. Correct?


Correct.

QUOTE
Just wanted to ask : can different filters possibly affect sound staging or timbre? Or are those qualities determined by other metrics?


They *can* definitely affect timbre, if the effects of the filter reach down into audible frequencies, but no properly designed filter should do that. On the other hand, there is a lot of "audiophile" gear where the rule book has been thrown out of the window and bad design is justified with voodoo.
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Yahzi
post Feb 23 2013, 18:23
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QUOTE
They *can* definitely affect timbre, if the effects of the filter reach down into audible frequencies, but no properly designed filter should do that. On the other hand, there is a lot of "audiophile" gear where the rule book has been thrown out of the window and bad design is justified with voodoo.


I always assumed that perceptions of sound staging were related to SPL, the source, physical positioning of speakers and the acoustical profile of the room. How would a digital filter affect sound staging? Assuming the DAC had a flat response and harmonic components 100 dB below the musical signal, how could that possibly be?

I've heard at least 5 times now in the past two days that the filter options on DACs can *definitely* affect timbre and sound staging. The article cited in support of this can be found here :

http://www.audiostream.com/content/what-ar...ence-labs-techn

Now I'm no EE, so I'm not qualified to make objective statements concerning this, but I would like to know from those experienced in the relevant fields what their take on this issue is. Thank you very much in advance!

This post has been edited by Yahzi: Feb 23 2013, 18:28
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Yahzi
post Feb 23 2013, 18:27
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Sorry, just to add : looking at those graphs, the THD was 0.0013 and 0.0026 respectively. That is ridiculously - no, extraordinarily low distortion. Are there any perceptual studies that show what our threshold of audibility is to harmonic distortion?
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greynol
post Feb 23 2013, 18:31
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Can and do are two different things. Personally, I'm only interested in the "do" and only when it can be proven through double blind experimentation. That said I wouldn't bother engaging people who can't satisfy this criteria.

This post has been edited by greynol: Feb 23 2013, 18:46


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Arnold B. Kruege...
post Feb 23 2013, 19:56
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QUOTE (Yahzi @ Feb 23 2013, 00:08) *
Hi there,

The claims I hear for audible differences existing for different electronics amount to frequency response, noise and distortion.

These distortion graphs are between the two I/V stages of a DAC :



And :



The claim is that these DACs measure flat, but the measurements show the effects of certain filters at play. Looking at the distortion components, is this enough of a difference to cause gross audible differences? The claims I hear are that different filters used in DAC design can result in audible differences irrespective if that DAC measured perfectly flat.

What do you think?


This might be a trick question because nobody I know can tell much about linear distortion by looking at an impulse response. What little I can discern from it says that it is probably fee of audible artifacts.

The FFT of its output spectrum shows nothing that could be audible All spurious responses sum to about 97 dB down.

Ask about the results of a level-matched, time-synched DBT. ;-)

The author's name looked familiar.

http://www.stereophile.com/writer/185

This post has been edited by Arnold B. Krueger: Feb 23 2013, 20:00
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Arnold B. Kruege...
post Feb 23 2013, 20:09
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QUOTE (Yahzi @ Feb 23 2013, 12:27) *
Sorry, just to add : looking at those graphs, the THD was 0.0013 and 0.0026 respectively. That is ridiculously - no, extraordinarily low distortion. Are there any perceptual studies that show what our threshold of audibility is to harmonic distortion?


The audibility of nonlinear distortion varies tremendously depending on the musical context and the SPL of the sounds you are auditioning. For music that has maximum masking potential, even a percent or two of first or second order distortion can go undetected.

I've done some work contriving musical sounds that maximize the audibility of nonlinear distortion and came up with something that would enable detection with some effort of less than 0.1 % (-60 dB) nonlinear distortion. Someplace around 0.03% nonlinearity, even that wouldn't work. That is -70 dB.

The audibility of nonlinear distortion is generally maximized with SPLs that are around 75-85 dB. Increasing the SPL so that it is above 80-90 dB appears to make the ear more nonlinear and its own nonlinearity masks the distortion in the source.

The usual rule of thumb is that if all spurious responses due to nonlinear distortion are >=80 dB down, then nobody is going to detect it, no matter what kind of nonlinearity and no matter what kind of music, speech or sound effects your source is. If you are really conservative use 100 dB down, and then you are totally safe.
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Yahzi
post Feb 23 2013, 20:44
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One of these days I'll book a flight to the States where I would love to meet some of you guys. Go through a few DBTs as well.... drinks on me. emot-3.gif
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Yahzi
post Feb 23 2013, 20:48
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QUOTE ("Arnold B. Kreuger")
I've done some work contriving musical sounds that maximize the audibility of nonlinear distortion and came up with something that would enable detection with some effort of less than 0.1 % (-60 dB) nonlinear distortion. Someplace around 0.03% nonlinearity, even that wouldn't work. That is -70 dB.


But with typical music content 0.1% nonlinear distortion is not going to be noticed?
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julf
post Feb 23 2013, 22:05
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QUOTE (Yahzi @ Feb 23 2013, 18:23) *
QUOTE
They *can* definitely affect timbre, if the effects of the filter reach down into audible frequencies, but no properly designed filter should do that. On the other hand, there is a lot of "audiophile" gear where the rule book has been thrown out of the window and bad design is justified with voodoo.


I always assumed that perceptions of sound staging were related to SPL, the source, physical positioning of speakers and the acoustical profile of the room. How would a digital filter affect sound staging? Assuming the DAC had a flat response and harmonic components 100 dB below the musical signal, how could that possibly be?


Again, what I said was "they *can* definitely affect timbre, if the effects of the filter reach down into audible frequencies, but no properly designed filter should do that". As in the filter will only affect timbre if it's cutoff frequency or slope is low enough to affect audible frequencies - something easily visible on a frequency response plot (but not on an impulse plot or intermodulation/distortion plot).

QUOTE
Now I'm no EE, so I'm not qualified to make objective statements concerning this, but I would like to know from those experienced in the relevant fields what their take on this issue is. Thank you very much in advance!


Well, I studied EE before moving into CS, and have since then worked on both audio and embedded signal processing...
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Arnold B. Kruege...
post Feb 24 2013, 14:24
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QUOTE (Yahzi @ Feb 23 2013, 14:48) *
QUOTE ("Arnold B. Kreuger")
I've done some work contriving musical sounds that maximize the audibility of nonlinear distortion and came up with something that would enable detection with some effort of less than 0.1 % (-60 dB) nonlinear distortion. Someplace around 0.03% nonlinearity, even that wouldn't work. That is -70 dB.


But with typical music content 0.1% nonlinear distortion is not going to be noticed?


True.


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Yahzi
post Feb 25 2013, 13:36
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This may be a silly question, but in terms of harmonic distortion (the "nice" kind) what would be a typical figure that one would expect to cause audible differences? 1%, 5% etc? I realise that one can't get a complete picture from a single THD measurement, but I would like to try and put things to perspective by comparing the miniscule harmonic distortion in the graphs to real world tube amps that people claim make the sound so lovely to listen to.

I realise the answer is probably going to be "it depends on ..." but any input on this would be appreciated. Thanks!
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Arnold B. Kruege...
post Feb 25 2013, 14:37
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QUOTE (Yahzi @ Feb 25 2013, 07:36) *
This may be a silly question, but in terms of harmonic distortion (the "nice" kind) what would be a typical figure that one would expect to cause audible differences? 1%, 5% etc?


Its not a silly question, and that applies to all honest questions no matter how basic.

The audibility of nonlinear distortion as you guessed is very dependent on the order of the nonlinear distortion and the sound being distorted.

The myth that even order distortion is more euphonic odd order distortion probably due to a number of facts:

(1) The first even order is second and the first odd order is third and as we all know 3>2. This relates to masking. Any frequency component that is closer to the fundamental is more likely to be masked by it. The second harmonic is always closer to the fundamental than the third harmonic and therefore it is more likely to be effectively masked. Note that push-pull amplifiers are inherently resistant to generating even-order distortion.

(2) Musical instruments are themselves generators of harmonics. The motion of the sound generators in musical instruments such as reeds, lips and strings produce varying amounts of nonlinearity. Plucking strings produces a sharp-edged stimulus that is something like an impulse, and a true impulse contains all frequencies. The commonly-used resonantors usually respond to harmonics as well. The natural harmonics in the music thus mask any harmonics that are created by failings of the equipment. It is possibly ironic that some musical instruments deliver much more energy as harmonics than as the fundamental component of the musical note.

The counterpoint is that any nonlinearity that produces harmonics also produces intermodulation. Intermodulation tends to produce component frequencies at frequencies that are not harmonically related to the fundamental. Note that most musical instruments have individual mechanisms for producing (different strings, different pipes, different resonators) each note. That tends to minimize intermodulation products and makes them more noticeable when produced by electronic or acoustic equipment.

QUOTE
I realize that one can't get a complete picture from a single THD measurement, but I would like to try and put things to perspective by comparing the miniscule harmonic distortion in the graphs to real world tube amps that people claim make the sound so lovely to listen to.

I realise the answer is probably going to be "it depends on ..." but any input on this would be appreciated. Thanks!


Under ideal conditions for masking, up to 10% or more THD can be masked by the music.

For example 10% THD is commonly used as a performance limit for subwoofers. This probably has a lot to do with the fact that bass notes then to be played one at a time and that most bass-producing musical instruments produce more energy as harmonics than fundamentals.

So there are your common limits of audibility for nonlinear distortion - from 0.1% to 10%. Current accepted practice seems to be to get under 0.1% by a factor of 2 or 3 wherever possible. Getting under 0.001% is always done for the purpose of inventorying and displaying leading zeroes! ;-)
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Yahzi
post Feb 25 2013, 17:54
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So if I told the DAC designer that his distortion graphs show harmonic products a 100 dB below the fundamental that basically invalidates his graphs as evidence of his user preference? You reckon 70 dB down is enough for distortion to be largely inaudible given the masking effects of music.
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Yahzi
post Feb 25 2013, 17:57
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Sorry Arnold, how do you work out the harmonic percentages in terms of how far below the signal is from the fundamental? I noticed 0.1 would be -60 below the fundamental and 0.03 would be -70. Please explain how that works. Thanks!
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Jplus
post Feb 25 2013, 18:30
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The dB scale is logarithmic. 20 dB means a difference by a factor 10. So 60 dB is a thousandfold difference and 70 dB is approximately three times that.
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julf
post Feb 25 2013, 18:31
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QUOTE (Yahzi @ Feb 25 2013, 17:57) *
Sorry Arnold, how do you work out the harmonic percentages in terms of how far below the signal is from the fundamental? I noticed 0.1 would be -60 below the fundamental and 0.03 would be -70. Please explain how that works. Thanks!


Wikipedia: Decibel
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DonP
post Feb 25 2013, 18:49
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QUOTE (Arnold B. Krueger @ Feb 25 2013, 08:37) *
The myth that even order distortion is more euphonic odd order distortion probably due to a number of facts:


One factor for it not being a myth is that the 2nd and 4th harmonics are the same note as the fundamental, just 1 and 2 octaves up. The 3rd isn't. Neither is the 6th, but by the time you get to the 6th harmonic the level is usually pretty far down.

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Arnold B. Kruege...
post Feb 26 2013, 02:04
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QUOTE (DonP @ Feb 25 2013, 12:49) *
QUOTE (Arnold B. Krueger @ Feb 25 2013, 08:37) *
The myth that even order distortion is more euphonic odd order distortion probably due to a number of facts:


One factor for it not being a myth is that the 2nd and 4th harmonics are the same note as the fundamental, just 1 and 2 octaves up. The 3rd isn't. Neither is the 6th, but by the time you get to the 6th harmonic the level is usually pretty far down.


While that is a fact, it might not keep the claim from being a myth.

While the case for the ugliness of aharmonic spurious responses seems pretty clear, the fact that the transposition doesn't end up at the same note seems to have a far weaker case.
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