Not finding a killer article on zobel networks/impedance equalization. Found this which is pretty easy:
R = Re * 1.25
C = Le / (R*R)
Also, from John Levreault's excellent article "A High Quality Dome Midrange/Tweeter Array" (Speaker Builder 2/88):
- Using an impedance chart, Fmin is the frequency of the minimum impedance, which would be R. F2 is the frequency that is 1.414 * R. So:
C = 1 / (2 * pi * F2 * R)
Mr Levreault then suggests that usually the values perform best if R = ~10% larger and C is 20-50% larger from the calculated values.
I *think* a new CDROM compilation of the Speaker Builder magazines is coming. I'll keep an eye out. There's so much goodness in these volumes.
Shannon