[sdiy] Multimode pole-mixing - building notch responses

[Donald Tillman]

If you have a Macintosh, there's a very nice math utility built in called Grapher.  It plots all sorts of math equations and it can be very helpful.  

It's hidden under the Utilities directory within the Applications directory, but you can get to it easily with command-space.

To plot filter transfer functions:
    Choose a log-log scale

    Write an equation defining s: 
        s = ix

    Add a second equation with the "+" box down below

    Make the second equation of the form:
        y = abs(...)
    (because you can't take the log of a negative number)

    And fill in your transfer function within that:
        y = abs((s^2 + 1) / (s^2 + s + 1))

The downside is that Grapher is not documented well.

  -- Don
--
Donald Tillman, Palo Alto, California
http://www.till.com