Rockbox Development > Feature Ideas
Even more EQ bands are necessary for many users
ZoSo:
There's a growing community of headphone enthusiasts on the Internet right now. You can find these people at websites such as Head-Fi. A lot of these people, myself included, have become very interested in the pursuit of accuracy and neutrality through the use of equalization. Using tools such as sine wave generators or in-ear microphones as reference, we can equalize our headphones to neutrality with great precision.
The current 8 peak bands is not enough for users like myself. The headphones I'm using with my Sansa Clip+ right now require 12 peak bands to be neutral when using the parametric equalizer on my PC. My EQ settings for another pair of my headphones on my PC have a whopping 26 peak bands.
JdGordon says here http://forums.rockbox.org/index.php?topic=42724.0 that the absolute maximum possible is 32 bands. I feel there would be many Rockbox users who would benefit from having all 32 of these bands available; 30 peak bands, the hi shelf and the lo shelf. More and more headphone enthusiasts are discovering the art of parametric equalization every day, so more and more Rockbox users are going to be finding the current 10 bands to be limiting to their needs.
wodz:
*IF* you need more then a few bands you totally miss the point of parametric eq, that is granted. Not speaking that it is a waste of cpu cycles which are rather limited in embedded systems. If you feel like needing such unusual setup feel free to modify the sources and recompile yourself.
AlexP:
Ten is already too many really on these systems. As wodz says if you want more you will need to build your own version.
saratoga:
I suspect if you're using 12 bands on a parametric EQ you may be doing something strange. Its pretty common for even pro-level mastering hardware to have only 7 bands. Can you post your EQ settings? Maybe I can give you feedback.
ZoSo:
--- Quote ---*IF* you need more then a few bands you totally miss the point of parametric eq
--- End quote ---
I respectfully disagree. I've experienced a lot of success making headphones fairly neutral in the past by removing their deviations from neutrality with parametric equalization, all while without creating audible (to my ears) artifacts. If I am creating artifacts, I can't hear them, so I really don't care. The post-ringing of minimum phase equalizers is generally masked by the signal itself anyways.
Headphone responses can have a lot of sharp treble peaks which are unkind to the ears and fatiguing and this is compounded by the tendency of headphones to create ear canal resonances.
I know the "conventional wisdom" is to use only a few, broad adjustments with a parametric EQ, but there would be no progress if everyone conformed to "conventional wisdom." I've had tremendous success equalizing out very narrow peaks and valleys in headphone response without creating audible (to my ears) artifacts. I listen to a sine wave generator to estimate the location, magnitude and Q of these peaks and to verify I've nulled said peaks.
--- Quote ---Not speaking that it is a waste of cpu cycles which are rather limited in embedded systems.
--- End quote ---
Well, obviously one would use less bands once they found it causing their music to lag/skip.
--- Quote ---Can you post your EQ settings?
--- End quote ---
Here's the EQ settings I just came up with for my Koss KSC75, which use 12 bands. Pic attached are these settings turned upside down so as to represent a quasi frequency response measurement, i.e. these are what the headphones sound like to my ears. The large 7.5 kHz peak is an ear canal resonance; the other peaks and valleys are limitations inherent in the driver. I set the precut to -10 and the result is the bass response is completely flat like a Stax headphone or Etymotic earphone, and I can confirm this by measuring the headphones with a microphone. The somewhat harsh quality of the KSC75's treble is nullified by removing the sharp peaks in its treble response which result from driver deviations from neutrality and the large 7.5 kHz ear canal resonance which all headphones tend to produce with my ears.
My settings for my PC equalizer:
Filter 1: ON PK Fc 128 Hz Gain -3.3 dB Q 1.00
Filter 2: ON PK Fc 20.0 Hz Gain 10.0 dB Q 0.80
Filter 3: ON PK Fc 60.0 Hz Gain -2.0 dB Q 1.00
Filter 4: ON PK Fc 144.0 Hz Gain -1.0 dB Q 0.20
Filter 5: ON PK Fc 3,829 Hz Gain 6.0 dB Q 5.00
Filter 6: ON PK Fc 1,968 Hz Gain -2.5 dB Q 8.00
Filter 7: ON PK Fc 4,600 Hz Gain -2.5 dB Q 10.00
Filter 8: ON PK Fc 5,400 Hz Gain 1.5 dB Q 10.00
Filter 9: ON PK Fc 7,500 Hz Gain -7.0 dB Q 7.00
Filter 10: ON PK Fc 7,000 Hz Gain -2.5 dB Q 10.00
Filter 11: ON PK Fc 8,500 Hz Gain -4.5 dB Q 7.00
Filter 12: ON PK Fc 11,600 Hz Gain -4.0 dB Q 7.00
I realize some of the really high Q value peaks are thought to be able to create artifacts, but again, I can't hear said artifacts. If the end user can't hear the artifacts, no harm done. I also feel the availability of higher Q values in Rockbox would be useful too, as the peaks in headphone response can be quite narrow at times.
In order to see how many users such as myself are doing this kind of equalization to headphones these days one only needs to google "eq site:head-fi.org," or "equalize site:head-fi.org."
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