
Simple Tilt equalizer
Type : Tilt References : Posted by neolit123 at gmail dot com
Notes : There are a few ways to implement this. (crossover, shelves, morphing shelves [hs>lp, ls>hp] ...etc)
This particular one tries to mimic the behavior of the "Niveau" filter from the "Elysia: mPressor" compressor.
[The 'Tilt' filter]:
It uses a center frequency (F0) and then boosts one of the ranges above or below F0, while doing the opposite with the other range.
In the case of the "mPressor"  more extreme settings turn the filter into first order lowpass or highpass. This is achieved with the gain factor for one band going close to 1. (ex: +6db > lp; 6db > hp)
Lubomir I. Ivanov
Code : //=======================
// tilt eq settings
//
// srate > sample rate
// f0 > 2020khz
// gain > 6 / +6 db
//=======================
amp = 6/log(2);
denorm = 10^30;
pi = 22/7;
sr3 = 3*srate;
// conditition:
// gfactor is the proportional gain
//
gfactor = 5;
if (gain > 0) {
g1 = gfactor*gain;
g2 = gain;
} else {
g1 = gain;
g2 = gfactor*gain;
};
//two separate gains
lgain = exp(g1/amp)1;
hgain = exp(g2/amp)1;
//filter
omega = 2*pi*f0;
n = 1/(sr3 + omega);
a0 = 2*omega*n;
b1 = (sr3  omega)*n;
//==================================
// sample loop
// in > input sample
// out > output sample
//==================================
lp_out = a0*in + b1*lp_out;
out = in + lgain*lp_out + hgain*(in  lp_out);

Comments
Added on : 29/05/09 by neolit123[ AT ]gmail[ DOT ]com Comment : correction:
(ex: +6db > hp; 6db > lp)

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