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Multi-Way Conventional loudspeakers with crossovers

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Old 6th May 2005, 12:22 AM   #1
akunec is offline akunec  Canada
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Default Capacitor across sub terminals to reduce reactance

I was just wondering if putting a capacitor across the voice coil of a bass driver could reduce the reactance of the load, thereby making it easier for the amp to drive it?

Also, wouldn't the load draw less power since none is wasted in the imaginary impedance?

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Alex
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Old 6th May 2005, 01:08 AM   #2
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SOrt of, adding a resistor there two will create a zobel network, this will flatten out the impedance curve that naturally rises due to the self inductance of the voice coil.

In a subwoofer I dont think this is worth doing the sub driver is directly driven by the amplifier yes?

The driver will also probably have a lowpass on it around 80hz or even less. The rise from self inductance will most probably be way past this frequency, so the amp will not even be driving the sub at frequencies where the impedance rises.

Do you mean something else?
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Old 6th May 2005, 01:20 AM   #3
soongsc is offline soongsc  Taiwan
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If your sub has a crossover built in, most probably it would have an RC zobel built in. The thing that mighrt effect the amp is the natural resonance point where the impedance peaks. This would require an RCL zobel. It is best to test the impedance curve and design the zobel if necessary. If the peak is real high, like over twice the nominal impedance, then you might consider the zobel. Otherwise it might not be necessary.
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Old 6th May 2005, 01:34 AM   #4
akunec is offline akunec  Canada
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The reason I brought this up was because I read in my EE book that if you hook up a capacitor in parellel with a table saw (inductive motor), you can reduce your power costs to it because the inductive load will be cancelled out by the capacitive load.
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Old 6th May 2005, 09:09 AM   #5
soongsc is offline soongsc  Taiwan
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The power saw power conservation is a different issue. In the power saw application, you are changing the phase of the current so that the power factor is better. It is possible because you are tuning only to one frequency. If a power saw has different speeds, I would think you'd have to switch caps for each speed.
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