hi guys Im on a music tec course at uni and im playing with some DSP. Ive been able to successfuly create some simple code for low and high pass filters where you just input a center frequency but now im trying to further that by adding a q variable also. The equations for the coefficents are highlighted in red. Ino the rest of the code works as it should because when i just change the coeficents values depending on the filter it works. But when i change them to these it plays no sound and the variable y which is my output doesnt contain any samples. In a nut shell the equations in the text book what am i doing wrong to translate them into my code? thanks guys hope im making sense On a side note before you think it im not asking you to do any work for me, this is further reading.

b0=k/(k^2*Q+K+Q) or b0=k/(k^2*(Q+K+Q)) not quite sure what you want. similar for the rest, you need to add a bracket to group the denominators together otherwise you will end up doing the wrong calculation. Dont ask me about making time pass stuff, I am struggling with the Fourier Transforms of the time series for now.

It seems that your brackets are all wrong. It should be something like this: b0=K/(K*K*Q+K+Q); b1=0; b2=-K/(K*K*Q+K+Q); a1=(2*Q*K*K-2*Q)/(K*K*Q+K+Q); a2=(K*K*Q-K+Q)/(K*K*Q+K+Q); However I dunno the purpose of these formulas .. so

Thank you very much. Basicly i failed high school maths. So the basic maths that every one expects you to know some of it i struggle with. Like in the equations from the text book, where to put the brackets, or which variables you times by each other. So what i was after was how to write out the equations in the text book. Which you both showed and now my band-pass filter works. I can sweep through center frequencies and controll the bandwidth basicly a notch filter. The purpose of the forumlas are that they calculate coeficents to put into a transfer function (or the nice easy filter function in matlab) so that you can create various forms of filters and controll their parameters.