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  #1  
Old 02-26-2011, 06:26 AM
shady_slim shady_slim is offline
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Default what is the width of the "q" parameter in Rockbox EQ?

Hello,

This is my first post here. Before starting this thread I searched the forum, I have also read carefully the RB manual, but could not find an answer to my question.

I have Sansa Clip+ with RB v. 3.7.1 and Phonak PFEs with green and gray filters.

PFEs are great phones - much better than my previous ones, yet I am not fully happy with either filters: the quantity of bass with the green ones is OK, but the quality - not - they seem to dampen all frequencies but med- and upper bass (including lower bass!) - which is not acceptable for me.
The bass quality with the gray filters is very good to me - it is fast and detailed, also at the very lowest end, but the amount of it is just too low and the higher frequencies are just too overwhelming to me.

Of course - the black filters could be a solution, as their signature is somewhere in between the gray and green ones, however, I chose first to play with EQ settings on my Clip+ to see how satisfactory results can be achieved with it. Then I may buy the black filters just to have comparison of the EQ capabilities and the filters.

Knowing the characteristics of Phonak`s gray filters (the diagram is available on many sites - also here at abi) I would like to make it as linear (or rather sloping a bit down as the frequency goes up) using the advanced/graphical EQ. Actually - I have already done some EQing, but am not sure how accurate it was - just because I do not know how the "q" parameter works at different frequencies...

My guess is the width of the "q" changes with frequency - e.g. q=1 at 100 Hz means 100 Hz +/- 10Hz (so we can @ 100 Hz it is 20 Hz "wide"), while q=1 at 4000 Hz means 4000 Hz +/- 400 Hz (so we can say @ 4 kHz it is 800 Hz wide).

In the example above q=1 width is equal to 20% of the frequency it is applied at both for the frequency of 100 Hz and 4 kHz. So we could say it is a constant ratio parameter. Of course - it is just my assumption - it does not need to be constant and it may be calculated in a totally different way. But even if it is constant - the original question returns - how wide is it?

I will appreciate your help!
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  #2  
Old 04-09-2011, 04:44 AM
orby orby is offline
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Default

your basical idea is right, and your concerns about that it probably wont be exactly as you think are reasonable as well.

you should get all information neede here

http://en.wikipedia.org/wiki/Equaliz...#Parametric_EQ
http://en.wikipedia.org/wiki/Q_facto...quality_factor

this is how it should be. dont know if rockbox treats it exactly like this.

Last edited by orby; 04-09-2011 at 04:53 AM.
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eq, equalizer, q width, rockbox

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