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Old 7th July 2003, 08:05 PM   #1
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Default Zobel and Notch query

Hi

Is it necessary to use a Zobel on a woofer when your crossover freq is at the point or just lower where impedance begins to rise?

The Dayton 8" woofer's impedance begins to rise around 350hz. I'll be crossing it over at or below 300hz but probably only with a 1st order (perhaps 2nd).

Also, does using a notch to reduce the bump at resonance mess up my values in WinISD? I assume it does as it's using the FS for it's calcs.

Any help appreciated.

Mos
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Old 8th July 2003, 01:15 AM   #2
Ron E is offline Ron E  United States
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The impedance rise will reduce the slope of a lowpass crossover by ~3dB/oct or so. If you account for this, you may omit the zobel. I'm not sure why are you using an impedance peak filter? How are you using the woofer? Is the crossover lowpass or highpass, what are all of the xo points for the system, what other drivers are you using....

Regardless, Fs is Fs, and when placed in an enclosure, Fs will change to Fc=Fs*sqrt(Vas/Vb+1) The resonant peak filter will only modify the input impedance, not the parameters....
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Old 8th July 2003, 02:02 AM   #3
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Ok.

2 x Dayton 8" woofers
1 x Vifa P13 mid
Morel MDT 20 tweeter

XOs look like 300 and 3500.

I was going to take the P13 lower to it's natural rolloff at around 125-150 but I'm worried that I may be asking it to do too much. It's rated at 40w nominal.

Ron E:

Quote:
The impedance rise will reduce the slope of a lowpass crossover by ~3dB/oct or so.
So if the slope was 12db it would make it 9? (15?)

Thanks

Mos
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Old 8th July 2003, 11:36 AM   #4
Ron E is offline Ron E  United States
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9dB - but it depends on the woofer and how inductive it is, It is hard to make a general statement.... Best is to measure and simulate with ?Speaker Workshop or?

If you are worried about excursion with the P13, then simulate it in a bass program in the size box you will use.

3-ways are a bit tricky....I hope you can make measurements.
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