CHANGSTAR: Audiophile Headphone Reviews and Early 90s Style BBS
Main Deck => Discussion for Registered Members Only => Topic started by: Marvey on June 28, 2012, 01:22:46 AM
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I will experimenting with measuring harmonic distortion... I have wanted to do these graphs for the longest time!!!
Measurements were taken with headphones calibrated to 87db A-weighted SPL with white noise. D2 - D5 in the below graphs represent 2nd to 5th harmonics at each frequency. Short primer: ideally when a certain tone is played, say a 100Hz sine wave, the headphone should only reproduce the 100Hz tone, and nothing else. However, in the real world, when we play a 100Hz sine wave, we will see all sorts of garbage (distortion). Any extraneous tones being reproduced which are multiples of the original tone are called harmonic distortion. For a 100Hz tone, 2nd order distortion is 200Hz (100x2). For a 500Hz tone, 4th order distortion is 2000Hz (4x5).
Below is the HP1000 harmonic distortion graph. It measures fairly flat in the bass, but yet it sounds quite bassy. This is because of the high level of 2nd harmonic distortion. The second harmonic amounts to another bass tone being played (less loudly) exactly one octave higher to augment the original tone. I will post post other headphones for comparison. BTW heavy 3rd order harmonics in the bass tends to make it sound one-note, undefined, or indistinct. Lots of overall harmonic distortion makes bass sound muddy. There is no such thing as "good" distortion.
Finally, note that the lines below represent specific orders of harmonic distortion, not THD or total harmonic distortion. I think it's fair to say that 1% or even 0.5% is easily audible.
(http://www.changstar.com/images/distortion/hp1000.jpg)
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Yes! Now I'll be able to figure out which headphones I shouldn't try to get and EQ up the sub-bass on.
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Exactly, you totally understand the concepts behind this.
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There is no such thing as "good" distortion.
Are you sure?!
I read on head-fi that it depends on what you like. :D
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DT1350 Harmonic Distortion
(http://www.changstar.com/images/distortion/dt1350.jpg)
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W3000ANV harmonic distortion
(http://www.changstar.com/images/distortion/w3000.jpg)
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TH900 Harmonic Distortion
(http://www.changstar.com/images/distortion/th900.jpg)
Low distortion in the bass (best so far.) 2nd order < 1%. Everything else < ~0.1%. But what's going on at 3-3.5kHz? This actually makes sense since there is ringing ~7kHz (as seen on the CSD), thus the 2nd harmonic spike near 3.5k. There are some other inter-relationships going on with the CSD too if you examine it and can do some simple multiplication.
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Would it be possible to compare Harmonic Distortion of certain modded vs. un-modded headphones? (KSC-75 vs StratoKOSSter, or T50RP vs Paradox) I have a feeling that those mods would likely bring up sub-bass and fix some other FR issues in the pass-band without amplification of non-linear distortion (a limitation that digital/analog equalization faces)
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yes, later.
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STAX SR007mk2 harmonic distortion
(http://www.changstar.com/images/distortion/SR007mk2.5.jpg)
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So purrin completes the triumvirate: FR, CSD, HD. Well done sir! If I might only indulge upon you to add a THD line.
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*raises hand*
Sir, I still don't quite understand what to make of the graphs. Or rather, the y-axis and how that relates with frequency range.
P.S., do I need to reintroduce myself in the appropriate section?
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Since these charts are log based I would like see the 0.5 tick between each major interval.
Looking nearer at the charts I see each line as I should have noticed before....now I can see it.
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Well done!
What does the 6k spike on the O2 2nd harmonic translate to in listening?
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Just means that a 6kHz tone will result in another 12kHz tone (2nd harmonic) about -24db down. I checked the CSD - no ringing at 12kHz. Probably benign because it's high up and just in a narrow area.