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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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9th Dec 2016, 10:32 am | #1 |
Hexode
Join Date: Feb 2007
Location: Luton, Bedfordshire, UK.
Posts: 454
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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 |
10th Dec 2016, 2:03 pm | #2 |
Dekatron
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 4,924
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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 |
10th Dec 2016, 6:02 pm | #3 |
Rest in Peace
Join Date: May 2003
Location: Harlaxton, Lincolnshire, UK.
Posts: 3,944
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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. |
10th Dec 2016, 7:21 pm | #4 |
Hexode
Join Date: Feb 2007
Location: Luton, Bedfordshire, UK.
Posts: 454
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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 |
10th Dec 2016, 7:25 pm | #5 |
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,061
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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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10th Dec 2016, 8:51 pm | #6 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
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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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11th Dec 2016, 9:48 am | #7 |
Hexode
Join Date: Feb 2007
Location: Luton, Bedfordshire, UK.
Posts: 454
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Re: Resistor in series with inductor in crossover.
Thanks for confirming I have some WW available.
Mike |