Rockbox Technical Forums

Rockbox General => Rockbox General Discussion => Topic started by: Nalilord on March 20, 2007, 05:34:01 AM

Title: Accurate EQ correction for iPod Earbuds
Post by: Nalilord on March 20, 2007, 05:34:01 AM
Hi there, though i have Shure E2 and Sennheiser HD25,
i always felt a potential in those standard Apple earphones.

So after I finally found its frequency response graph, and according
to the information on http://www.headphone.com i created
a wonderful EQ-preset.

Download the preset here: http://rapidshare.com/files/21915018/iPodAccurate.cfg.html

Or create it yourself:

Enable EQ: Yes
Precut: -6.0 dB
Advanced EQ Settings:
Low Shelf Filter -> Cutoff Frequency: 90 Hertz
Low Shelf Filter -> Q: 0.7 Q
Low Shelf Filter -> Gain: 6.0 dB
Peak Filter 1 -> Center Frequency: 250 Hertz
Peak Filter 1 -> Q: 0.5 Q
Peak Filter 1 -> Gain: 2.0 dB
Peak Filter 3 -> Center Frequency: 2700 Hertz
Peak Filter 3 -> Q: 0.8 Q
Peak Filter 3 -> Gain: -10.0 dB
High Shelf Filter -> Cutoff Frequency: 12000 Hertz
High Shelf Filter -> Q: 0.7 Q
High Shelf Filter -> Gain: 4.0 dB

(http://farm1.static.flickr.com/151/427932743_ce4040fc29_o.png)

// from headphone.com:

A natural sounding headphone should have a gentle hump in the bass (about 3 or 4 dB) between 40Hz and 500Hz. (This compensates for the fact that headphones don’t give you the physical punch that the sound from a speaker has; so a slight compensation of increased bass is needed for natural sound.) Headphones also need to be rolled off in the highs to compensate for the drivers being so close to the ear; a gently sloping flat line from 1kHz to about 8-10dB down at 20kHz is about right.
Title: Re: Accurate EQ correction for iPod Earbuds
Post by: lights0ut on March 20, 2007, 07:26:33 PM
cool, I actually use the original earbuds still (too lazy to go buy new ones) so I will give this a try, thanks ;).
Title: Re: Accurate EQ correction for iPod Earbuds
Post by: Shovas on March 21, 2007, 10:27:23 PM
I don't suppose the same could be done for Philips HE592 Surround Sound Ear Buds?

Yeah, I'm asking a favour. I have no idea how to do it. :)
Title: Re: Accurate EQ correction for iPod Earbuds
Post by: saratoga on March 21, 2007, 11:45:05 PM
I don't suppose the same could be done for Philips HE592 Surround Sound Ear Buds?

Yeah, I'm asking a favour. I have no idea how to do it. :)

Heres how I do it:

http://forums.rockbox.org/index.php?topic=9313.msg71779#msg71779
Title: Re: Accurate EQ correction for iPod Earbuds
Post by: deceasekain on March 22, 2007, 08:51:41 PM
Wow!
that sounds really good
Title: Re: Accurate EQ correction for iPod Earbuds
Post by: mannequin on March 22, 2007, 10:21:48 PM
this sounds like a great method to adjust the rockbox eq but i'm confused about the graph of these particular headphones since all the spikes are going on closer to 20,000 Hz:

(http://graphs.headphone.com/graphCompare.php?graphType=0&graphID[]=603)

any advice how to go on about it would be appreciated.
Title: Re: Accurate EQ correction for iPod Earbuds
Post by: soap on March 22, 2007, 10:37:52 PM
Don't forget that when creating EQs based upon graphs alone, and especially when doing so on iPods with low-impedance loads, you need to use two graphs.  Graph one being the frequency response of the headphone, and graph two being the frequency response of the player when loaded with said phones.
Title: Re: Accurate EQ correction for iPod Earbuds
Post by: Febs on March 23, 2007, 01:33:08 PM
Well, there's also HRTF (head-related transfer function) to take into consideration as well.
Title: Re: Accurate EQ correction for iPod Earbuds
Post by: soap on March 23, 2007, 01:51:51 PM
Well, there's also HRTF (head-related transfer function) to take into consideration as well.

Oh, I assumed HeadRoom was using a mannequin head for their tests.
 ;D
Title: Re: Accurate EQ correction for iPod Earbuds
Post by: Febs on March 23, 2007, 01:55:29 PM
Good point.

Title: Re: Accurate EQ correction for iPod Earbuds
Post by: saratoga on March 23, 2007, 02:00:43 PM
The use a simulated head.  In general i don't trust those things, but their results for the HD-280 are really, really close to what I got using foobar's EQ and my own ears.  Don't know about their results for IEMs or anything like that, but they seem to do quite well for studio headphones.