As said above , the impedance of a driver will show a peak at resonance, and then a slow rise from the nominal impedance with increasing frequency. A Zobel network typically consists of a series network of a capacitor and a resistor connected in parallel with the woofer. The purpose of the Zobel network is to cancel the rise in impedance which is caused by the driver's voice coil impedance. In effect, the voice coil impedance is resonated out using a capacitor.
Here are a couple short online articles that do a decent job with impedance graphs and pictures of a typical simple zobel circuit. Sometimes they help.
http://www.trueaudio.com/st_zobel.htm
http://www.loudspeakers101.com/ZoblFilt.htm
Sincerely
I remain
Here are a couple short online articles that do a decent job with impedance graphs and pictures of a typical simple zobel circuit. Sometimes they help.
http://www.trueaudio.com/st_zobel.htm
http://www.loudspeakers101.com/ZoblFilt.htm
Sincerely
I remain