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How do zobel networks help the sound of a speaker?
- Thread starter djnagle
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Detailman
Addicted to tweaking
All drivers have impedance peaks and zobels are designed to minimize them.
This helps the speakers perform their best in frequency ranges they were designed for.
You can always not attach the zobel to the crossover but across the woofer terminals.
That gives you the possibility of trying both ways. With or without.
This helps the speakers perform their best in frequency ranges they were designed for.
You can always not attach the zobel to the crossover but across the woofer terminals.
That gives you the possibility of trying both ways. With or without.
Paul C
Super Member
[Joe Pesci in My Cousin Vinny]The woofer's voice coil is... what?... come on, you know the answer! Shout it on out! Yes, a coil, with an iron core (well, a magnetized iron core). It is an inductor.[/Joe Pesci in My Cousin Vinny]
At low frequencies the impedance will approach the voice coil resistance (Re). At higher frequencies impedance will rise using the exact formula as is used to calculate a 6 db/oct ("1st order") crossover, using the woofer's Re and Le. You can calculate that frequency of that rise the same way you would with an inductor and using, for example, 8 ohms for a woofer.
So what you want to do is put a resistor that is approximately the same resistance as Re (actually, Re x 1.25 = Rz works even better) with an appropriate capacitor, calculated to that same frequency, will flatten that rising impedance. Since most 8 ohm impedance woofers actually have a Re of 5 to 6.5 ohms, just using an 8 ohm resistor will work just fine. And Radio Shack has some nice 8 ohm, 20 w non inductive resistors that will do the job here.
You can actually put the formulas together to calculate the capacitor value. I've done that in an Excell worksheet that is hosted here on the site.
Right click and "Save Target As"
http://audiokarma.org/forums/attachment.php?attachmentid=26564&d=1159591082
Just fill in the blanks.
OK, but back to the question, what will a Zobel do for you? The woofer with zobel will now appear as a more constant impedance, especially in the region where the crossover is working. So, the crossover will work more "as predicted" by the formula or charts you are using.
About the Speaker Design worksheet, you can fill in the blanks and get answers for box volumes for ported and sealed cabinets, port lengths, crossover values for 6 db/oct and 12 db/oct crossovers, including zobel values. The sheet will not give you bass response. You will need to use Boxplot or some other program for that. But this sheet gives a "quick and dirty" calculation.
At low frequencies the impedance will approach the voice coil resistance (Re). At higher frequencies impedance will rise using the exact formula as is used to calculate a 6 db/oct ("1st order") crossover, using the woofer's Re and Le. You can calculate that frequency of that rise the same way you would with an inductor and using, for example, 8 ohms for a woofer.
So what you want to do is put a resistor that is approximately the same resistance as Re (actually, Re x 1.25 = Rz works even better) with an appropriate capacitor, calculated to that same frequency, will flatten that rising impedance. Since most 8 ohm impedance woofers actually have a Re of 5 to 6.5 ohms, just using an 8 ohm resistor will work just fine. And Radio Shack has some nice 8 ohm, 20 w non inductive resistors that will do the job here.
You can actually put the formulas together to calculate the capacitor value. I've done that in an Excell worksheet that is hosted here on the site.
Right click and "Save Target As"
http://audiokarma.org/forums/attachment.php?attachmentid=26564&d=1159591082
Just fill in the blanks.
OK, but back to the question, what will a Zobel do for you? The woofer with zobel will now appear as a more constant impedance, especially in the region where the crossover is working. So, the crossover will work more "as predicted" by the formula or charts you are using.
About the Speaker Design worksheet, you can fill in the blanks and get answers for box volumes for ported and sealed cabinets, port lengths, crossover values for 6 db/oct and 12 db/oct crossovers, including zobel values. The sheet will not give you bass response. You will need to use Boxplot or some other program for that. But this sheet gives a "quick and dirty" calculation.
