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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 9th Dec 2016, 10:32 am   #1
Whaam68
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Default Resistor in series with inductor in crossover.

Hi
I'm refurbing a pair of leak sandwich speakers (original 15r 2 way). The 3W resistor in the crossover circuit measures 28r and should be 22r. Is the inductor at one end and cap at the other impacting my dvm reading across the resistor or has it just drifted and replace? Also it looks like a large carbon type. Ok to replace with a WW if indeed required.
Thanks
Mike
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Old 10th Dec 2016, 2:03 pm   #2
Bazz4CQJ
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Default Re: Resistor in series with inductor in crossover.

Basic WW resistors may show inductive effects and therefore affect frequency response. Carbon resistors are probably the safest option.

B
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Old 10th Dec 2016, 6:02 pm   #3
ukcol
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Default Re: Resistor in series with inductor in crossover.

Your resistor is over 25% above its nominal value so even if it is a 20% type it is out of tolerance. I don't think measuring it in circuit will give a false high reading. Sometimes you can get a false low reading if there are parallel components in the circuit. The circuit must be powered down and any large electrolytics discharged of course.

I would not hesitate to use a wire-wound for a replacement as the inductance of the resistor will be too small to be significant at audio frequencies. If I am in error with that last statement someone will no doubt put me right.
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Old 10th Dec 2016, 7:21 pm   #4
Whaam68
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Default Re: Resistor in series with inductor in crossover.

Thanks guys. I was being lazy and will whip it out anyway and test out of circuit I was just curious. I was surprised how high it was reading.
Mike
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Old 10th Dec 2016, 7:25 pm   #5
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Default Re: Resistor in series with inductor in crossover.

Inductors for a crossover are hundreds of microhenries, whereas the inductance of a wirewound resistor is maybe a microhenry (as against nanohenries for carbon types). Important for some applications but here the effect will be diluted! So use ww with confidence!
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Old 10th Dec 2016, 8:51 pm   #6
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Default Re: Resistor in series with inductor in crossover.

It's a low value resistor, so a wirewound one will have particularly low inductance. Only people with hearing into the megahertz region need worry.

500nH into 8 Ohms+22 Ohms will give a 3dB roll-off at 30 = 2 x Pi x f x 500E-9

which solves to 9.5 MHz

David
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Old 11th Dec 2016, 9:48 am   #7
Whaam68
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Default Re: Resistor in series with inductor in crossover.

Thanks for confirming I have some WW available.
Mike
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