Creating an IIR filter

[Citrus]

Hi

Anyone now how to generate an IIR file from an normal eq curve?

Want to add a bit of bass and treble to my hqp app.

Shapers and filters dont quite do enough for me?

C.

 

[yamamoto2002]

Algorithms section of this page explains it. h is frequency response of uniform frequency interval (EQ curve). n is number of sample points of frequency curve of h.  b is numerator polynomial coefficients array of IIR filter and a is denominator polynomial coefficient array. Matlab + signal processing toolbox home user license costs about $200. I don't know free software solution

https://www.mathworks.com/help/signal/ref/invfreqz.html

 

 

[Citrus]

Thanks yamamoto2002

I think I’ve reached the limits of my audio knowledge!

it still adds up in the audio knowledge bank. A few days ago I’d never heard of an iir filter.

Seems ive reached the point of a whole new level of audio using HQplayer.

 Thanks C

[yamamoto2002]

Thanks. I recommend the book "understanding digital signal processing" by Richard G. Lyons to grasp what IIR, Z-transform, w(k) and those strange fractional polynomial equation means. This particular problem (IIR EQ design) is not explained in the book but it covers all the basics including FIR EQ filter design and IIR lowpass filter design and it is fascinating read.

 

BTW I wrote an article about FIR EQ filter design procedure to take a de-emphasis EQ as an example. 

https://yamamoto2002.blogspot.com/2020/11/designing-de-emphasis-digital-filter.html

[Citrus]

Thanks

Super star : )

[NOMBEDES]

IIR.   Intelligence Information Report?    OP should spell out his acronym after first use.  Then he is free to use it at will.

[Citrus]

My Intelligence, I’mhappy to report, is zero! xxxx

[opus101]

This might come in useful - https://shepazu.github.io/Audio-EQ-Cookbook/audio-eq-cookbook.html

[Citrus]

Thanks opus101

Ill get reading : )

C.

[yamamoto2002]

On 5/17/2022 at 7:05 PM, opus101 said:

This might come in useful - https://shepazu.github.io/Audio-EQ-Cookbook/audio-eq-cookbook.html

 

Thank you for providing info about biquad IIR filter, it is possible to perform parametric EQ by cascading several "low shelf" "highShelf" "peakingEQ" in serial

[Citrus]

Thanks