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# BS2B for Equalizer APO
Channel: ALL
Preamp: -0.1 dB
# This preamp command is disabled because I reduce the volume with M/S mixing before crossfeed
# Preamp: -1.7 dB

# Set cross frequency and cross gain here
# Use BS2B config
Eval: Fc=700
Eval: level=6

# The next two lines mid to M/S, makes mid channel quieter, and mixes back to R/L
# This is optional and is not a part of BS2B. If you want to change how quiet the mid channel gets
# Change the "-1.6db" value
Copy: M=0.5*L+0.5*R S=0.5*L+-0.5*R
Copy: L=-1.6dB*M+S R=-1.6dB*M+-1.0*S

# These parts are based on bs2b-H-transform.pl from http://bs2b.sourceforge.net/
Eval: s=sampleRate
Eval: Gd=level*-5.0/6.0-3.0;
Eval: Adh=level/6.0-3.0;
Eval: G=10^(Gd/20);
Eval: Ah=10^(Adh/20);
Eval: Gh=1-Ah;
Eval: Gdh=20*log10(Gh)/log10(10);
Eval: Fch=Fc*(2^((Gd-Gh)/12));
Eval: fc=Fc/s;
Eval: d=1/2/pi/fc;
Eval: x=exp(-1/d);
Eval: fch=Fch/s;
Eval: dh=1/2/pi/fch;
Eval: xh=exp(-1/dh);

Eval: a0=1; b1=0;
Eval: a1=-x;
Eval: b0=G*(1-x);

Eval: a0h=1;
Eval: a1h=-xh; b1h=-xh;
Eval: b0h=1-Gh*(1-xh);

Copy: LX=R RX=L
Channel: L R
Filter: ON IIR Order 1 Coefficients `b0h` `b1h` `a0h` `a1h`

Channel: LX RX
Filter: ON IIR Order 1 Coefficients `b0` `b1` `a0` `a1`

Copy: L=L+LX R=R+RX