What headphone?

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Distortion comes mostly from source / improper volume control / replaygain screw-up / bitrate mismatch etc.
 
Every headphone on earth will distort if you turn the volume to unsafe values. Note that they all have a "maximum input power", which is well beyond what is needed to make you deaf.

I'm fairly certain that the distortion from the source / amp will be at least a whole order of magnitude, possibly even two, lower than the distortion from the headphones. I think a similar topic to this appeared in the sound science forums a short while ago, and that was the conclusion. Typical amplifiers may have a THD + noise of 0.05%, whereas most headphones will have THD between about 0.5% and 1% in the midrange.
 
To the OP, I suggest you have a look through the resources page over at Inner Fidelity, where Tyll has put together various measurements for a fairly large range of headphones.
 
Quote:

jerg said:

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Distortion comes mostly from source / improper volume control / replaygain screw-up / bitrate mismatch etc.
 
Every headphone on earth will distort if you turn the volume to unsafe values. Note that they all have a "maximum input power", which is well beyond what is needed to make you deaf.

Click to expand...

 

Didn't the LCD2 get a great, flat, response when Tyll measured them?

They're great cans - I'll have to get a pair one of these days.

Amps aiming designed for low distortion (as opposed to euphonics = added distortion) can get much lower than 0.05% easily.  A $20 FiiO E5 running off of a puny rechargeable battery can get 0.005% THD into a load like 150 ohms.  The topic creator wasn't specific about distortion, but there are many other kinds of distortion as well.  IMD is also an important parameter, though there are obviously many ways to measure and test that as well.
 
In addition to Tyll's website:
http://www.innerfidelity.com/headphone-data-sheet-downloads
 
There are some THD / IMD results for a given set of test tones (but not over the range of frequencies) at HeadRoom and this Japanese geocities site.  They have even more headphones covered:
http://www.headphone.com/learning-center/build-a-graph.php
http://www.geocities.jp/ryumatsuba/review.html
 
Keep in mind that low-frequency distortion is relatively difficult for humans to hear.  Also, the type of harmonic distortion produced is important as well.  2nd order harmonics (an octave above) and maybe 4th etc. tend to be relatively benign and harder to notice than others at a given power level.  3rd order and other odd harmonics tend to be worse.  Frequencies totally unrelated to the source are of much much greater concern.  So the absolute THD value isn't giving a complete picture of the type of distortions contained therein and thus how audible it may be.
 
Quote:

arleus said:

I'm fairly certain that the distortion from the source / amp will be at least a whole order of magnitude, possibly even two, lower than the distortion from the headphones. I think a similar topic to this appeared in the sound science forums a short while ago, and that was the conclusion. Typical amplifiers may have a THD + noise of 0.05%, whereas most headphones will have THD between about 0.5% and 1% in the midrange.
 
To the OP, I suggest you have a look through the resources page over at Inner Fidelity, where Tyll has put together various measurements for a fairly large range of headphones.

Click to expand...

 

mikeaj said:

 
In addition to Tyll's website:
http://www.innerfidelity.com/headphone-data-sheet-downloads
 

Click to expand...

 
Thanks, that link was very useful. There is a PDF of all the measurements here: http://www.innerfidelity.com/images/AllGraphs.pdf
 
I was curious to find headphones with the best impulse response and lowest distortion. The Stax headphones seemed to be the best of the lot, though lots of notable headphones were not included.
 
You're right, of course, about THD ratings. It's almost meaningless, but better than nothing. I'd rather compare IM distortion and odd order harmonics.

Stax 2170/lcd 2.2?