TOPIC:

Hi all!

A user at our swedish forum came up with this question.

The existing analog filter is this one:



Is it possible to get the miniDSP to simulate this kind of filter? I tried using the house curve in REW and then exporting the biquads, but I cant get any filter parameters in REW if there is no measurement.

Any ideas?

Thanks,

/Bo

Bo,

We can't see your pic of your filter for some reason so hard to say what filter you're talking about. With this said, there are quite a lot of resources online for doing an "Analog to Digital" filter conversion. The first google pick is actually well documented.
www.beis.de/Elektronik/Filter/AnaDigFilt/AnaDigFilt.html

Check it out, it's a bit math intensive but shouldn't be that hard.

DevTeam

Thanks! That was a really great article on converting analog filters into digital.

I fixed the pic by attaching it rather than linking it.

Great reference, unfortunately your Biquad calculations and those in the reference do not agree. They agree except for the signs of the "a" coefficients (use a BW 2nd order low pass for example). I get the same signs as the reference and can derive the frequency response from these values, but when I use the values as provided by your "calculator" the results are incorrect.

Comments?

Hello Gedlee,

Sorry, forgot to mention that one... You actually need to reverse the signs of a1 and a2 since it's the implementation of Analog Device DSP. We've meant to update the "text" area of the plug-in to automate the sign reversalm, but didn't and since then a couple of people developed some custom spreadsheets/REW calculator and such based on this implementation. We ought to include this oddities in the help file though so we'll do it shortly.

A good thread worth looking at is the following one:
www.minidsp.com/support/forum/3-suggesti...orm?limit=6&start=12

You'll find a spreadsheet which may help you..

Hoping this info helps and sorry for the confusion

DevTeam