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Old 19th September 2009, 03:08 AM   #1
AllenB is offline AllenB  Australia
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Default How do you design a zobel

My front mains are peaky above 1kHz and the crossover only has an inductor. I think I can improve things by adding a zobel network across the woofer out terminals of the crossover but I need a formula I can use. I don't want to measure the impedance, I'd rater do trial and error but I need the formula to put me in the right starting place.
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Old 19th September 2009, 03:57 AM   #2
tinitus is offline tinitus  Europe
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how big is your inductor
what kind of woofer
what kind of tweeter
are there no cap on tweeter
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Old 19th September 2009, 04:07 AM   #3
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A Zobel reduces the rising impedance of the woofer...you need to have the DC resistance (measure with a meter) and the Le (electrical inductive equivalent of the driver)( from the T/S specs.

Then it's: Rz = Re x 1.25
Cz = Le / Rz^2

Where Rz is the zobel R, Cz is the zobel C.
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Old 19th September 2009, 04:07 AM   #4
AllenB is offline AllenB  Australia
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how big is your inductor....don't know. By looking I'd guess no bigger than 150mH
what kind of woofer....6 inch kevlar cone
what kind of tweeter....1 inch silk dome. Rolls off below 2k.
are there no cap on tweeter....4.5uF and small value adjustable resistor.

Oh, and there is no available value for Le.
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Old 19th September 2009, 04:15 AM   #5
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Quote:
Originally Posted by AllenB View Post

Oh, and there is no available value for Le.
Given the lack of available information and your obvious aversion to effort, you'd best forget about a zobel.

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Old 19th September 2009, 04:26 AM   #6
AllenB is offline AllenB  Australia
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To be honest, I'm not even sure whether the full zobel would be a good thing. The crossover was obviously designed to be an improvement on the raw drivers and if I go full zobel I'll also have to re-do the inductor, then I'll need to re-do the tweeter. I'd rather buy better speakers.

I do appreciate your help. I measured re as 3.8 ohms so I'll try a 4.7 ohm resistor.
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