Impedance Equalization Circuit Designer / Calculator Help
Use the Impedance Equalization Circuit Designer
Impedance Equalization Circuits, also know as Zobel circuits, are used to counteract the
rising impedance of a voice coil caused by inductive reactance. This problem mainly occurs in sub
woofers, because of their large coils. A Impedance Equalization circuit is usually placed after the
A Impedance Equalization Circuit is simply a capacitor (C) and a resistor (Rc) in series,
in parallel with the driver.
Re = Driver DC Resistance in Ohms
Le = Driver Inductance in mH
Say you have a 8 Ohm tweeter with a Re of 5.7 Ohms with a Le of .08 mH
The impedance curve for the driver would look like this.
|Actual Driver Resistance|
|Desired Driver Resistance|
The impedance of the tweeter rises because of the voice coils inductance at high frequencies.
Using the above formulas, C = 7.13 uF and Rc = 1.58 Ohms. Using the capacitor and resistor will
help to flatten out the impedance curve. Experimentation is recommended to achieve the desired