Sigma Studio -> Linkwits Transform

Hello mga2009,

If you really want to use these coefficients you can enter them into the General 2nd Order filter cell. Here are the details:

https://wiki.analog.com/resources/tools-software/sigmastudio/toolbox/filters/general2ndorder/iircoefficient

However, why don't you simply use the crossover cells that are available in the library? They use Linkwitz/Riley filters and are easy to use.

I had put together this example project for a 2-way crossover to a mono sub as an example file a while back.

ADAU1701 Crossover with Sub Output.zip

I think this will work fine for you.

There is a help page for the crossover but it does not explain much. Fortunately the GUI interface is easy to understand.

https://wiki.analog.com/resources/tools-software/sigmastudio/toolbox/filters/crossover

Dave T

Dave,

Thanks for your quick reply! I will thoroughly check the information.

I've been testing your suggestions and found the General 2nd Order filter cell is accepted, but using "Stimulus and Probe" to check it is working, I don't get the correct equalization...

After switching the a1 and a2 signs (left the a1 as a negative number and a2 as a positive number) , it seems to work.- Is this a glitch in SigmaStudio?

Leaving it like this, it seems to work:

b0 1,001259526446320
b1 -1,996288114509760
b2 0,995053284904683
a1 -1,996297042315250
a2 0,996303883545513

Also, I noticed using the cell "Parametric EQ" in "Second Order" - "Double Precision" - "Multichannel" is also doable, but here the "minus" sign does not have the same effect.

Thanks

Please don't consider the "commas" in the numbers above... I am using "." in SigmaStudio.

Still when I use "Parametric EQ" cell with IIR Coefficient and IIR Table I get a different response than when using "General 2nd Order filter" cell with IIR Coefficient. (The difference is made by the "-" sing in a1 and a2.

UPDATE:

Here I uplooaded a picture that shows using the same IIR Coefficients and the same simulated response, but the "parametric Equalizer Param EQ! window does not show the proper equalization (If I switch the "-" sign between a1 and a2 it shows a correct equalization, but the simulated response fails.

Hello mga2009,

I think this is a slight difference in the implementation. There are a lot of posts on the subject. It is not a glitch.

Dave T

Thanks Dave,

I uploaded a picture showing the difference between the simulated response and the "Parametric Equalizer" window. Anyway, I will test it with General 2nd Order and download it to my DSP. Thank you for your help.

Hello mga2009,

I have just read your questions with great interest. I have been dealing with the problem of transferring the coefficients of the Linkwitz transform into Sigma Studio for a long time. Have you found a solution in the meantime. If so, do the rules generally apply to all filters?
I am looking forward to your answer

Many greetings from Berlin, Germany

Yes.

Thanks to Dave's help and some reading here in EngineerZone I managed to properly implment the LT in SigmaStudio.

Sigma Studio doesn't have a 'Linkwitz Transform' filter block, so the solution is to implement it as a IIR filter.

The coefficients are calculated with the spreadsheet in the MiniDSP site, and from the info I've read (credits to all those who found/though of this), the spreadsheet and Sigmastudio use different definitions of coefficients a1 and a2, so you have to multiply the spreadsheet's a1 and a2 values by -1 before plugging them into Sigmastudio.