Hi guys,
I've started a blind test on distortion over on head-fi that you can do. I would appreciate your feedback as you guys are probably more knowledgeable about this sort of thing.
To sum up things so far. (copy and paste from head-fi)
Here are the files
Free File Hosting Made Simple - MediaFire
I've done something to the files that will shed light on to something that is mentioned a lot but I have never seen any evidence on. I'm not going to tell you what the differences are but it's not compression related or any special effects etc. If you do the test I would like you to PM me which ones you think sound the best, in order too if you can. If you can't tell the difference say that too. Once I get 20 results or so I'll tell you what I've done.
The song is the first 25s of Chan Chan by the Buena Vista Social Club but if someone can suggest a good reference song for this test I can apply the same thing to that song too.
Thanks for your help.
Edit: Added first 35s of Evil Ways by Santana
Edit: Added the songs in zip files
Well I've got about 10 results now and they're fairly consistent so I'll tell you what I did. I have added 5% harmonic distortion in the different harmonics from 2nd to 5th plus there is the original. The general consensus so far in best to worst sounding is
original -> 3rd -> 2nd -> 5th -> 4th
about 25% can't distinguish any difference (I suspect it may be more because I've had a lot more downloads than results) 50% can distinguish only the 4th and 5th and 25% can just distinguish between the rest also.
This is how I did it, please tell me if it was wrong.
Took the original flac I had and upsampled to 24 bit wav.
Imported to matlab and added harmonic distortion by using the Chebyshev n polynomial of the original waveform to create nth order harmonic distortion.
multiplied the by 0.05 and added it to the original wave form.
converted to 24bit flac so I could use replay gain
downsampled to 16 bit wav applying replay gain and dithering.
So far the results seem to indicate that the odd harmonics are favoured to even ones isn't that the opposite of what we're told?
I've started a blind test on distortion over on head-fi that you can do. I would appreciate your feedback as you guys are probably more knowledgeable about this sort of thing.
To sum up things so far. (copy and paste from head-fi)
Here are the files
Free File Hosting Made Simple - MediaFire
I've done something to the files that will shed light on to something that is mentioned a lot but I have never seen any evidence on. I'm not going to tell you what the differences are but it's not compression related or any special effects etc. If you do the test I would like you to PM me which ones you think sound the best, in order too if you can. If you can't tell the difference say that too. Once I get 20 results or so I'll tell you what I've done.
The song is the first 25s of Chan Chan by the Buena Vista Social Club but if someone can suggest a good reference song for this test I can apply the same thing to that song too.
Thanks for your help.
Edit: Added first 35s of Evil Ways by Santana
Edit: Added the songs in zip files
Well I've got about 10 results now and they're fairly consistent so I'll tell you what I did. I have added 5% harmonic distortion in the different harmonics from 2nd to 5th plus there is the original. The general consensus so far in best to worst sounding is
original -> 3rd -> 2nd -> 5th -> 4th
about 25% can't distinguish any difference (I suspect it may be more because I've had a lot more downloads than results) 50% can distinguish only the 4th and 5th and 25% can just distinguish between the rest also.
This is how I did it, please tell me if it was wrong.
Took the original flac I had and upsampled to 24 bit wav.
Imported to matlab and added harmonic distortion by using the Chebyshev n polynomial of the original waveform to create nth order harmonic distortion.
multiplied the by 0.05 and added it to the original wave form.
converted to 24bit flac so I could use replay gain
downsampled to 16 bit wav applying replay gain and dithering.
So far the results seem to indicate that the odd harmonics are favoured to even ones isn't that the opposite of what we're told?
I would not necessarily be surprised to learn people favour odd (or high order) harmonic distortion in a short passage such as your test.
Higher orders tend to introduce artifacts that often are interpreted as sounding "cleaner", brighter and/or more detailed by some, especially over the short term. Recording engineers have a vast arsenal, and they use it, to deliberately introduce distortions in music.
So, it's a fallacy to assume everyone naturally gravitates to the lowest order distortion version of a music recording. I would only expect a trained ear to immediately recognize the distortion signature in the files you've created.
Although it would be much harder, I think a better test would be to create two otherwise identical amplifiers with two different feedback loops, and match the gain. In this way you could create two devices that would always add mostly low order or mostly high order harmonic distortion while (hopefully) limiting each to the identical total harmonic distortion figure.
This would give an opportunity to introduce listener fatigue to counteract the preference for artificial detail added by the introduced higher order harmonics.
Higher orders tend to introduce artifacts that often are interpreted as sounding "cleaner", brighter and/or more detailed by some, especially over the short term. Recording engineers have a vast arsenal, and they use it, to deliberately introduce distortions in music.
So, it's a fallacy to assume everyone naturally gravitates to the lowest order distortion version of a music recording. I would only expect a trained ear to immediately recognize the distortion signature in the files you've created.
Although it would be much harder, I think a better test would be to create two otherwise identical amplifiers with two different feedback loops, and match the gain. In this way you could create two devices that would always add mostly low order or mostly high order harmonic distortion while (hopefully) limiting each to the identical total harmonic distortion figure.
This would give an opportunity to introduce listener fatigue to counteract the preference for artificial detail added by the introduced higher order harmonics.
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I listened to the first one and said "what happened to the high end' ? Then I pulled out my Santana from a CD and played it and mine is as I expected. So where did you get that copy? I'm not sure how to get you a copy of mine to compare but I think you'd be surprised. Mine was not any special version, just the Columbia Santana's Greatest Hits.
G²
G²
It should be very good it's an MFSL UDCD, Santana - Santana Ultradisc II™ 24 KT Gold CD - Mobile Fidelity Sound Lab, Inc.,
I downloaded it from the net though, (cough), so maybe it's not.
You can email me your version at jagduley at gmail.com if you like.
Cheers,
James
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Extremely clever test! And one that I'd generally encourage except for a major caveat: if this is illegally downloaded and distributed material, anyone participating is at risk, especially in the US. Many record companies are extremely aggressive about copyright enforcement and the penalties are very, very high. I won't touch it, much as I'm curious to give it a spin.
It's not the downloading that gets the record companies legal mavens excited, it's distribution. That's why the favorite victims of record company action are kids and non-computer-savvy people who 'share' their entire music collection to the P2P networks.
So, we're probably OK in downloading the files (downloading is still legal in Canada, not in USA) but the Portshill should check his situation in Oz about the legality of distributing.
I do think the Fair Use thing would apply in any case.
And with millions of illegal downloads every day, this would be a stupid target for action...not that that gives me any reassurance- just look around....
So, we're probably OK in downloading the files (downloading is still legal in Canada, not in USA) but the Portshill should check his situation in Oz about the legality of distributing.
I do think the Fair Use thing would apply in any case.
And with millions of illegal downloads every day, this would be a stupid target for action...not that that gives me any reassurance- just look around....
What he said.
Fair Use (USA) and Fair Dealing (everywhere else) would protect you when the intent is research or study.
In some jurisdictions the brief length of your tests alone would be sufficient to dismiss any allegation of copyright infringement since many places hold that a fraction of one song simply cannot be infringement under any conditions.
If that didn't apply, you can offer the research defence, and I don't see anything in your post or your process that would negate that.
The RIAA and the MPAA in the US have shown they are very reluctant to sue anyone that might actually have a defence. The US's SONY Betamax decision still stings 30+ years later. They were sure they would win that one (and the law said they should) but instead the Justices gave them the concept of "Fair Use", which that court more-or-less invented as a defence to VTR infringement (since home taping of TV was not previously considered fair use; it was actually prohibited by statute), and ruled for the defendant.
Bonus would be the free legal team ... too many universities would have an interest in you prevailing for them to risk you losing; a judgement against you would be also a judgement restricting them. ;-)
If it really bothers you, I'm sure we could find a performance by some musicians who actually own the copyrights (ie original composition, not signed by a label, since the labels always demand all the copyrights when they take you on) who would grant you rights to use for the purpose.
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Metallica doesn't actually believe that, or at least they sure want their own lawyers to be exempt.
We can go to Shakespeare, though:
King Henry the Sixth, Part II, on or about 1591 A.D.
"The first thing we must do is kill all the lawyers," - (Act IV, Scene II).
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Added another song
I've added In the water by Annie and the Beekeepers from mastersfromtheirday.com which is available as a free download so should be legit.
In-the-water.zip
I've added In the water by Annie and the Beekeepers from mastersfromtheirday.com which is available as a free download so should be legit.
In-the-water.zip
Interesting results. Could you be more specific (detailed) on processing that you've done?
sure here is my matlab code
Code:
function hd(filename)
l = 35; %length used in seconds
[or,fs,N] = wavread(filename,[1 44.1e3*l]); %import first l seconds from wav
hd2nd5p = or + 0.05*(2*or.^2 - 1); %adds 5% 2nd harmonic distortion
hd3rd5p = or + 0.05*(4*or.^3 - 3*or); %adds 5% 3nd harmonic distortion
hd4th5p = or + 0.05*(8*or.^4 - 8*or.^2 + 1); %adds 5% 4nd harmonic distortion
hd5th5p = or + 0.05*(16*or.^5 - 20*or.^3 - 5*or); %adds 5% 5nd harmonic distortion
n=length(filename);
wavwrite(hd2nd5p,fs,N,[filename(1:n-4) 'hd2nd5p.wav']) %exports to wav with the same filename with hd2nd5p on the end
wavwrite(hd3rd5p,fs,N,[filename(1:n-4) 'hd3rd5p.wav'])
wavwrite(hd4th5p,fs,N,[filename(1:n-4) 'hd4th5p.wav'])
wavwrite(hd5th5p,fs,N,[filename(1:n-4) 'hd5th5p.wav'])
wavwrite(or,fs,N,[filename(1:n-4) 'or.wav']) %exports the original (first l seconds)it's pretty simple basically I just applied the Chebyshev polynomials - Wikipedia, the free encyclopedia that for a full scale pure sine wave give the harmonic of the order of the polynomial (in practice with a non fullscale sine wave you get some of the lower order harmonics as well and with multiple sine waves (ie music) you get intermodulation non harmonics).
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