[Sonido]

I was looking through various headphone spec sheets on innerfidelity (much appreciated Tyll Hertsens for all the headphone data) and on the distortions graph they take both 90dB and 100dB distortion levels. It seems for most headphones, outside of maybe the lowest frequencies, the 100 dB has lower distortion levels than the 90dB, albeit it's usually more jagged compared to the 90 dB. Anyone know why the higher dB produces lower distortions? I always intuitively thought that with more volume and power the distortions would go up as the drivers would have to physically swing more distance causing less control of the diaphragm.

 

[MindsMirror]

The THD produced by the headphone at those frequencies and levels is not significant and it is below the noise floor of the measurement (it is a THD+noise measurement after all). In that case what it is really telling you is the dynamic range. If you increase the signal level and the noise floor stays constant, the dynamic range is increased.

 

[castleofargh]

I imagine there isn't just one answer to that. if the measurements were done in an anechoic chamber, that would take some variables out of the equation as external noises are definitely integrated into those measurements. I'm getting pretty mad with that and waiting late at night to measure stuff, because headphones are nocturne creatures and they perform better at night

(what else could it be???? ^_^)
if you pick up outside noise, then when increasing the volume in the headphone, you end up with more dynamic between the signal and the noise. that could be one good reason.
 
 
now about actual distortion/noise, I don't think there is a rule saying that they all must follow exactly the volume level. when THD+N goes up with the loudness it's a sign that the driver doesn't like that volume level. but when it goes down? outside of noise IDK.
 
 
maybe ask the man himself?

 

[watchnerd]

This isn't unique to headphones.  This can be common in other transducers.
 
Even if excursion goes up, if the driver is still within its linear excursion range, distortion can remain somewhat constant (or decrease at a slower rate than volume) as volume increases, which leads to a lower % at higher volumes...up to a point.
 
Once the driver approaches / exceeds its linear excursion limit than it all goes to hell very quickly and distortion climbs exponentially.
 
Classic examples of this are some subwoofers that have huge linear Xmax excursions.

 

[serman005]

Thank you guys for explaining this!