how to get the biquad filter as eq?

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farbstoff-fabrik

how to get the biquad filter as eq?

Post by farbstoff-fabrik »

Hi there,

I am working on a module and bascially i would like to add a eq that bootst the frequency at 300 (similar to the stock CA 3 band equaliser). I have spend 2 evenings on this but for some reason my approach doesn't work.

I am using a biquadfilter with a peakingeq as filtertype. freq set to 300,0 and gain is set by a knob with a value of 1 to 12. I presume 12 is the dB gain you are adding?

(from memory... :)

--
BiQuadFilter = eq new BiQuadFilter(filtertype.peakingeq, 300.0, 0, 0);

--
eq.SetFrequency(300.0);
eq.SetdbGain(boostKnob.GetValue());
signalOut = eq.ProssesSample(signalIN);

--

When I start turning the knob, it doesn't boost anything. The input signal seems unprocessed.

Any help is very very much appreciated!

Thanks in advance!

-Matt
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utdgrant
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Re: how to get the biquad filter as eq?

Post by utdgrant »

In the constructor, the parameters are:

BiQuadFilter(FilterType type, double frequency, double gain, double bandwidth)

The bandwidth parameter is defined as the number of octaves, and you've set it to 0.0.

This seems like asking for trouble! :)

Try it at 1.0 instead, and see if that makes any difference.
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farbstoff-fabrik

Re: how to get the biquad filter as eq?

Post by farbstoff-fabrik »

Ah, it might be the decimal and number :)

have you had experience with the biquad? I'll try later today to get it to work.

btw: also on this topic: viewtopic.php?p=1606&hilit=biquad#p1606
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utdgrant
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Re: how to get the biquad filter as eq?

Post by utdgrant »

farbstoff-fabrik wrote: Thu May 12, 2022 9:47 am have you had experience with the biquad? I'll try later today to get it to work.
No, no experience at all.

I've seen Bi-Quad coefficient calculators online, and most of them don't let you
set 'Q' to be lower than 0.1. I suspect it will lead to divide-by-zero errors
somewhere down the line.

Your problem might have nothing to do with this. It's just a suggestion.

Hope you find your answer,
Grant
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farbstoff-fabrik

Re: how to get the biquad filter as eq?

Post by farbstoff-fabrik »

If I do - i'll post it :)
farbstoff-fabrik

Re: how to get the biquad filter as eq?

Post by farbstoff-fabrik »

In the meantime I have spoken to a few other developers and it seems I am not the only one experiencing issues setting this biquad up. After another afternoon and half a evening i gave up. Could someone from cherryaudio clarify, please :D thanks in advance!
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