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Inductor or resistor?!
Inductor or resistor?!
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Old 19th June 2020, 08:17 AM   #1
10mH is offline 10mH
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Default Inductor or resistor?!

Hi this is my first post in this forum. I am trying to restore a pair of German made ALR Nummer 4 speakers which I picked used. There is a crossover board inside which for the midrange and the tweeter and a separate board for two woofers. On the mid-tweeter board, there are two components which looks like resistors but had 47RJ written on them. They are as big as a 3W resistor. are these resistors or 4.7uH inductors ?? How can I find it? I replaced them first with 3W carbonresistors and sound became very shouty which is not at all close to the working pair I have. But when I used a 0.82ohm small 0.25W resistor it sounds close to the good speaker which made me think this was an inductor more than a resistor.

What is the difference between wirewound resistor with value 4R7 and inductor 4R7?
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Old 19th June 2020, 08:54 AM   #2
Johno is offline Johno  Australia
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Inductor or resistor?!
J is usually the tolerance (F = +- 1%. G = +- 2%. J = +- 5%. K = +- 10%) and R is the decimal point all for fixed resistors.
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Old 19th June 2020, 08:57 AM   #3
KatieandDad is offline KatieandDad  United Kingdom
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The inductance of a 4R7 wirewound resistor shouldn't be audible.
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Old 19th June 2020, 09:44 AM   #4
KatieandDad is offline KatieandDad  United Kingdom
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Just reading your post again. 47RJ is 47 Ohms not 4R7.

If you have used 4.7 Ohms instead of 47 Ohms then the speakers will be very different.
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Old 19th June 2020, 02:22 PM   #5
Galu is offline Galu  Scotland
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I wouldn't regard it as essential to replace the original resistors in the first place.

Concentrate on old bipolar electrolytic capacitors, where fitted. Electrolytics are the crossover components most worthy of replacement.

If you must replace the resistors then ensure a minimum power rating of 5W.
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Old 22nd June 2020, 04:42 PM   #6
10mH is offline 10mH
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Quote:
Originally Posted by KatieandDad View Post
Just reading your post again. 47RJ is 47 Ohms not 4R7.

If you have used 4.7 Ohms instead of 47 Ohms then the speakers will be very different.
No mine is 4.7. By the way I found the difference myself. There can be 4R7 resistor and 4R7 inductor. They both look stickingly similar. Resistor has a resistive core. Inductor has iron core.


Example: 4x MICC-4R7K-02 Drossel Draht THT 4,7uH 0,38A 0,65Ω O3,3x63mm +-10% Q | eBay

Thatís an inductor looking like a resistor
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Old 22nd June 2020, 05:06 PM   #7
maton00 is offline maton00  Mexico
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4.7uH has no use in a common audio crossover your whole wiring will measure almost the same inductance, test with a cheap cemented 5W 4.7 ohms, you may not tell with ears alone, if it keeps you out of sleep, you may need a microphone and test equipment to ensure it has a good flat response, memory and ear alone can't be properly used to optimize that kind of systems.
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Old 22nd June 2020, 09:18 PM   #8
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I really donít know the purpose of this, but when I replaced it on an existing crossover with one having lower current rating (like 200mA, 500mA..) it changed the sound to really thin. I think depending upon crossover design it may make a difference. The one I have if from ALR Nummer 4 which if I Am not wrong was designed by Karl Heinz Fink from Fink audio consulting. Still I am not claiming it makes difference in all cicuit. I tried removing them and bypassing them, but there too it was making a huge change in tonality.


In the circuit I am talking about itís connected in series with an array of 10x parallel 10uF MKT 373 capacitors. May be effect is exaggerated by this design?
 

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