Hello everyone,

I search the SigmaStudio wiki, and I still not figure out how to make a filter that contain db/oct design

If I want to design a High or Low pass Shelf / Butterworth filter with db/oct design, which block should I use (I am using AD1701)?

I only find the butterworth design in the Crossover block.

sorry I am noob on SigmaStudio EQ design

Hope you guys can help me!

Thanks!

Regards,

Alvis.

Hello Alvis,

Here's what blocks to use in order to implement these filters:

Lowpass & HighpassSix dB per octave filters can be implemented with the

First-Order Filter Block:By definition these are

Butterworthfilters ("maximally flat in their passband."). They're analogous to the simple RC filters in the analog world.You can also do these filters with the

General Second-Order Filterblock. Here you get the advantage of two selectable filters in one -- for example, a Lowpass and a Highpass together:If the General Second-Order Filter has enough "horsepower" to build two 6 dB filters, it's reasonable to expect it could make one 12 dB filter. And it does! Here we can select a Second-Order Butterworth filter:

The "horsepower" comes from a more sophisticated algorithm involving two delays and two feedbacks (compared to one each for the First-Order filters). With the whole block dedicated to one filter, it becomes analogous to Second-Order analog filters which include either an inductor or an extra cap plus an op-amp.

Need even more dB per octave? You can cascade several filters. Though you can do this manually, you'll need to choose differing

Qand sometimes frequency for each section to get optimal results. TheNth-Order Filterblock does this math for you. The last time I looked it only works for even-numberedN-- in other words, it cascades only Second-Order filters, although the theory allows you to mix First-Order and Second-Order filters.Shelving FilterChoose the General Second-Order Filter and set its drop-down menu to

Shelving. You can change the slope with the knob as shown below. Likely there's a formula to translate dB per octave to the setting of this knob, but it hardly matters since the slope cannot be entered numerically anyway.Best regards,

Bob