filter response using library modules?

Plugins & Modules
1

Hi all,

I’d like to evalutate the frequency response of a given filter using the library modules (free would be nice). Usually I take a impulse of 1024 samples, feed in to the filter, and then set SPAN plugin with the same window in the end of the chain.

This way, I can visually see the freq response of the given filter.

Any way to do this with Rack modules? A impulse generator + an analyser with settable window?

Thanks :slight_smile:

2

You need the not free HOST module, called Host FX, there you could load your VST plugin. Have several Voxengo plugins working this way.

3

IR can be uploaded to convolvzilla from nysthi. And it’s free.

1 Like
4

https://vcvrack.com/plugins#Host

5

Thanks for the replies guys! I got Host, its like I’d like to use VCV modules related stuff instead of external resources.

Learning somethings more and (maybe) different strategies to get the freq responses…

6

Sending white noise to a filter then to an analyser is a good way to visualise the curve!

1 Like
7

I didn’t even know there was another way to do XD

8

Impulse has a terrible crest factor, so if there is any noise in the filter it will be a problem. better is perfectly uniform noise, and best is a sinewave sweep. Have you looked at the Bogaudio FFT spectrum analyzers? They are very good.

1 Like
9

You want a Bode plot of \log |H| vs \log f, right? You could use an oscillator to generate a pure sine sweep and look at the result on a frequency analyzer. Or you could generate a 1-sample impulse and look at that on an analyzer.

Or do you want a waterfall plot? Or an impulse plot? Or a plot of poles/zeros? I’m not clear what you want.

10

Thanks for the answers :slight_smile:

Usually (example on a biquad filters), I evalutate freq response with zeros and poles. This give to me the graph of how each band is filtering, visually.

I’d like to do the same analysing others kind of filters, not mine, to see its freq response. So, with filter that I don’t own code, I send a 1-sample impulse to span plugin (every, for example, 1024 samples), and I sync sample to that windows.

So, visually (on span plot), I can see the “response” slopes of the filter, as if the filter I’m analysing have a visual graph plot.

For example: which would be the plot of this filter? cf/src/CUTS.cpp at v1 · cfoulc/cf · GitHub Such as show (in SPAN) this:

image

Is it more clear now?

11

Depends on the setting on cf Cuts. The High cut will look something like this with white noise fed in.

whiteNoiseCuts
whiteNoiseCuts1515×792 461 KB

Other’s will look like this:

whiteNoise
whiteNoise1920×1080 645 KB