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How to calculate the coefficients to control the "General(2nd-Order)" filter?

Question asked by liangbread on Apr 29, 2014
Latest reply on Apr 30, 2014 by JJoseph

Hi John,

 

    I am now trying to control the "Genera Eq"  from my MCU.On the calculation of the coefficients of the different filter type,it seems to be two version of formulas of the "Parametric" type filter by referring to the "SigmaStudio Help".In the "Filters" part the formulas used to calculate the coefficients showed as the image below:

RM$EIJEM6EEWV9H]2LRBI_F.jpg

    Similarly but not the the same,while in the "EQ Algorithm" part,as showed in the image below,the formula on the "alpha = sin(w0)/(2*Q)" is different from the above with the "A" coefficient excluded here.

EY{RO@AX0L0GU%6C1Q~50]K.jpg

      In my sigma studio,the "Parametric" filter type was chosen,but the formulas to calculate out the 5 coefficients of it are according to the "Peaking" filter,for which the "Transfer function" is the same as the "Parametric" filter.Even though,after altering the "Parametric" filter to "Peaking" filter the 5 coefficients to be sent out while tuning from the sigma studio are different.

      All in all,I am just confused by the calculation formula of the 5 coefficients.Why do I have to control the "Parametric" filter with the formula of the "Peaking" filter?

 

Best Regards,

Liang

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