@duma
I'm assuming that you have already tried to match the built in Filters with your Target. Properly using analysis and metering. You should at this point already know what your target filter frequency response looks like at a glance.
Example: Lowpass filter on a saw wave. Using Minimeters, we can clearly see the shape of the filter. And we can try and match this shape in Hise. We can see a little resonance and a "not very steep" cutoff. That gives us immediate clues for matching it.
5b176446-ebc1-4d84-a887-6cff0619a8fa-image.png
Assuming you've already done this, I would next recommend learning to port 3rd party c++ filters to Hise. You need to learn first how to create c++ custom nodes. There are some forum posts and videos about creating c++ nodes. Search the forum.
After learning this, you will be able to create / import c++ dsp into Hise. You can now search for open source filters on github, there are many good examples of analog and digital filters to be found there. You then need to download the source and work on building a c++ node which can run that dsp. You need to know c++ to do this.
After you've done that you can see if any of the filters you found suit your goal.
Now then, assuming you've looked at the frequency response of your target filter in the daw using metering, and you haven't been able to match that shape in Hise with any of the default filters or with any 3rd party filters, and you're dead set on creating a filter with the exact target frequency response, then here is some literature I'd look into:
https://www.researchgate.net/publication/3324749_Optimal_Design_of_Digital_IIR_Filters_by_Model-Fitting_Frequency_Response_Data
https://www.researchgate.net/publication/2901736_On_The_Design_Of_Iir_Filters_With_Arbitrary_Frequency_Response
https://www.researchgate.net/publication/335788005_Prony_Pad'e_and_Linear_Prediction_for_Interpolation_and_Approximation_in_the_Time_and_Frequency_Domain_Design_of_IIR_Digital_Filters_and_in_Parameter_Identification
