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Question: Zobel Impedance?
- Thread starter Nikko75
- Start date
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A Zobel network is to equalize the impedance so that as the impedance of the voicecoil goes up the Zobel will compensate and bring it back down. Since the Zobel is in parallel with the driver the resultant impedance will be lower than either of the parallel legs. If the Zobel resistor is the same as the driver then at some frequency the resultant impedance will be less than the driver alone and we don't want that, we want it to be flat after the resonant peak. You could possibly move the frequency up a bit and use a resistor equal to the driver's DCR but you'd probably have a bump where the 2 frequencies (inductive rise of the driver impedance and the Zobel resistance) meet.
Anyway, that's why you use a bigger resistor than the driver impedance.
Ray
Anyway, that's why you use a bigger resistor than the driver impedance.
Ray
Paul C
Super Member
Even though Re may be 5.8 - 6.8 ohms (typical for an 8 ohm woofer) its impedance is higher. It never presents a load that low to the amp. It is always higher than Re.
As Ray said, the purpose is to flatten out the impedance curve, present a more constant Impedance at any frequency, so that the crossover network works more as predicted.
As Ray said, the purpose is to flatten out the impedance curve, present a more constant Impedance at any frequency, so that the crossover network works more as predicted.
Nikko75
Listener and Music Lover
Yup I understood the purpose of a zobel but the higher than Re value was puzzling me but I did a simulation and now I see why. It effectively works the same as a crossover (but not lowering the transfer function magnitude) and if the R value was the same as the driver it causes the resistance to drop sooner and affects the crossover as noted above. In my situation that might actually be what I want. Thanks guys!