I asked the same question on dsp.stackexchange.com

But there nobody answered me. Maybe here anyone could help? I would be very appretiate.

I’am trying to calculate Fourier Transform for impulse response treated by equaliser. Situation like that:

Signal 1, 0, 0, 0… goes to some equalizer, and output of that equalizer goes to my FFT calculator Then I draw results on the graph - Magnitude(freq) and Phase(freq) - to see what some equalizers exactly do with frequencies and their phase.

And everything works well, until I use on EQ some extremely hight Q (very narrow bandwith) - for example Fabfilter Pro-Q. Then my graph jumps crazy. But not very crazy. Freq which I gained by EQ is OK, but all the rest around frequencies jumps together up/down/up/down/up/down… But that jumping ratio is not regular, it’s crazy

I don’t know why. How to fix it?

Of course my signal 1, 0, 0, 0… after normal EQ is changed as that there are values between 0 and 1 (sometimes little bit above 1 if gaining is high).

But I found out that after EQ with extremly high Q, in my signals there are a lot of negative values like `-0.000114598`

(it’s just example). Maybe I am wrong but I suppose they make my graph jumping. But how to manage with that? I tried to send to FFT absolute values of my signal, but it’s wrong way.

Thanks for any help.