Maybe this is getting off topic for this list...
But anyway...
On Apr 29, 2014 1:34 PM, "Balduin Waldmeister" <detlev24@xxxxxxxxxxx> wrote:
>
> Thank you for your replies. Maybe this concerns more the ALSA developers.
>
> Yes, the STX drives all kinds of headphones and most of them very well but it lacks on low impedance (<32 ohm) models. This is due to the headphone output impedance of 10 ohm on the STX and also on the new STX II. Thus it theoretically is perfect for headphones >80 ohm, although ASUS claims to have it (the old STX) optimized for headphones 32 - 600 ohm (probably by its drivers). Please see:
>
> http://www.innerfidelity.com/content/meridian-explorer-case-study-effects-output-impedance/ (an example to explain the "why?")
> http://www.asus.com/News/knWtTLpnXrb1YaqR/ (see "Headphone impedance")
>
> Instead of releasing a headphone output <10 ohm on the STX II (e.g., 2 ohm) to resolve the old STX's well known issue with low impedance headphones (16 - 32 ohm), ASUS seems to address it on their Window driver (only) for the STX II, as mentioned before.
>
> Right now, for the old STX, you find on AlsaMixer the following three settings:
>
> <64 ohms (which in reality is 32-64 ohm)
> 64-300 ohms
> 300-600 ohms
>
> Thus I really would appreciate - if possible - an additional 16-32 ohm optimization on ALSA for the old STX; enabling fun playback also on top notch low impedance headphones e.g., Fostex TH-900 (25 ohm) or Audeze LCD-XC (22 ohm).
>
> Best regards,
> Balduin
>
> PS: Maybe you are right and buying an additional headphone amp is the only way to go when using an old STX...
If you read the article you quote carefully, you should struggle to understand how some kind of digital processing can compensate for too-high output impedance into an arbitrary set of low-impedance headphones.
The point being the frequency response aberrations depend on the headphone in question's impedance at varying frequencies - not something that can be corrected for in an a priori fashion.
Also the damping problems created by too-high output impedance result in underdamped signal excursions which AFAIK cannot be fixed by some kind of frequency response filter.
Seems to me the logical thing to do would be to get a higher impedance set of cans, or maybe an outboard headphone amp with low output impedance.
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