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Source's harmonic distortion to the headphones

post #1 of 5
Thread Starter 

Ok, we know there is a threshold where we can decern the THD with our ears, but that's when it's coming out of the headphones.  

 

First of all, how do you measure distortions of headphones?

 

Second, how does the source/amp's distortions specs(measured) translate to the output(headphones)?  How much does it affect the output?

post #2 of 5
Quote:

Originally Posted by SilverEars View Post

 

First of all, how do you measure distortions of headphones?

 

In a similar hardware setup as the frequency response, but with different test signals (such as sine sweeps for measuring distortion vs. frequency).

 

Quote:
Originally Posted by SilverEars View Post
Second, how does the source/amp's distortions specs(measured) translate to the output(headphones)?  How much does it affect the output?

 

The overall distortion can generally be approximated by simply adding the distortions of individual components (amplifier, headphones, microphone, etc.). Although this is not necessarily accurate, because the harmonics resulting from the distortion may have different phase relative to the fundamental, and distortions from various sources can sometimes even partially cancel out each other, resulting in lower overall distortion. But addition can give a reasonable estimate. Also, if one component has much higher distortion at a particular frequency/level, then the low distortion from the others does not really matter much for the overall amount.

 

Dynamic headphones (and speakers) typically distort more at low frequencies and high levels. They can have decently low distortion in the midrange to treble at normal listening levels, but loud bass is often problematic with up to a few percents of distortion (or more especially in cheaper models, ear buds, etc.). Also, the bass distortion can cause intermodulation with the higher frequencies.

 

Well designed solid state amplifiers (especially for headphones) have fairly low distortion, and it is normally the lowest in the midrange. It can increase somewhat in the treble, because of less negative feedback being available to correct the distortion, and sometimes in the bass (due to power supply or thermal issues). A good headphone amplifier can achieve less than 0.01% from 20 Hz to 20 kHz, but for others (particularly tubes) it can be a few tenths of a percent.

 

The distortion of not too high quality electret measurement microphones can affect the results when measuring headphone distortion, mainly in the mid to high frequency range. At high SPL, it can be in the tenths of a percent range (mostly 2nd order), but it does not increase at low frequencies, so the headphones usually dominate the distortion there.


Edited by stv014 - 4/10/14 at 7:05am
post #3 of 5
Quote:
Originally Posted by SilverEars View Post

Second, how does the source/amp's distortions specs(measured) translate to the output(headphones)?  How much does it affect the output?

The level of distortion in headphones is generally an order of magnitude or more above the distortion in amps. In practice, the distortion of amps is so low, it just doesn't matter.
post #4 of 5
Thread Starter 

So what specs actually matter on the amps?  Or the source?  Because I could swear that some high-end phones are very transparent and can really reveal the source very well.

 

Which specs of the source can explain some sources performing better than others with a transparent headphone?


Edited by SilverEars - 4/10/14 at 5:15pm
post #5 of 5

Most amps and players perform well below the thresholds of human perception- even cheap ones. Here is a comparison between a pretty typical DAP and some of the best headphones made...

 

--------------------

 

Here is a review that measures the lowly iPhone 5G...

http://www.kenrockwell.com/apple/ipod-touch-5g/audio-quality.htm

 

Frequency Response: 20Hz to 20kHz +/- < .04dB

THD < .05%

 

--------------------

 

Compare that to the Audeze LCD-3...

http://www.headphone.com/headphones/audeze-lcd-3.php

http://www.innerfidelity.com/content/preliminary-investigation-audeze-lcd-3-and-lcd-2-page-2

 

Frequency Response: 20Hz to 20Khz +/- < 15dB

THD < 1dB

 

--------------------

 

The differences between the way a DAP performs and the way a set of headphones perform are massive. To put these in perspective, the thresholds of human perception while listening to music are approximately...

 

Frequency Response: 20Hz to 20Khz +/- 3dB

THD: 1dB

 

So, you can look at these figures and pretty quickly see that if there is anything to be heard, it's going to be coming from the headphones, not the player. Headphones don't "reveal" problems in sources. Subjectivists make stuff like that up to promote bogus concepts like "synergy".


Edited by bigshot - 4/10/14 at 6:06pm
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