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Alternate BPF and BSF Question
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February 11, 2015
9:40 pm
Forum Posts: 41
Member Since:
September 12, 2013
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I tried to implement the Alternate BPF and BSF from Zoelzer on the FXProjects Page. I tried the BPF but I have to divide the center frequency by 2 to have a correct result. I doublechecked my coeff calculation but found no fault.

Has someone else tried this formula?



February 12, 2015
9:55 pm
W Pirkle
Forum Posts: 247
Member Since:
January 29, 2017
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Hi Peter

It had been a while since I looked at this project so I dug up my original version and downloaded the project from the Bonus Projects page. I noticed that the project was missing the all-important .PRJ file, so I fixed this and uploaded a new version.

But, when comparing my equations to those on the Bonus Projects page, I did not have any issues with the center frequency for either BPF or BSF - they were spot on. I altered the project's coefficient calculation to be identical to the terms used on the Bonus Projects page (everything divided by delta).

You can download the project and compare that calculation in the .cpp file with yours.


Let me know if you find an anomaly, but I checked several times and it looks fine to me.

- Will

February 13, 2015
4:23 pm
Forum Posts: 41
Member Since:
September 12, 2013
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Hi Will,

thanks for the updated project. There is no relevant difference in our coeffs calculation. I replaced my calculation by yours. Still the same problem.

I implemented my calculation in a new class BQuad which is a copy of your BiQuad + the coeffs calculation and use this class for a 10 Band Stereo EQ. Anywhere in this implementation must be the factor 2 fault...



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