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Inductor wire thickness and sound

Objectivist01

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Hi I am repairing a high pass filter for a tweeter and want to use a 0.27mH Inductor in parallel the tweeter. The capacitor in series with the tweeter is 5,6uF and there is L pad resistance of 0.82 ohm. The inductor is now damaged (..physically) and I would need a replacement. Upon looking in different parts websites I came accross inductance of same value but of different thickness of wires .45 to 2mm! I understand the reactance of the coil varies with the thickness.
Can someone advice the formula to verify how the frequency crossover freq varies with the thickness ?
 

Speedskater

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Any real world inductor is in fact an inductor in series with a resistor. So the 0.45mm one will have about 20 times the resistance of the 2mm one. How this difference in resistance will impact the crossover functions, is above my pay grade.
 

March Audio

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Inductors should have their dc resistance shown in the specs. It's this that will vary for the same inductance value. How damaged is the inductor? Can you measure its dc resistance and replace with a similar? Alternatively measure the thickness of the wire and replace with similar, you really won't be far off.

You need to model the whole circuit and know the tweeter parameters to get anywhere near accurate results for the crossover behaviour.

Virtuixcad amongst others can do this.

https://kimmosaunisto.net/Software/Software.html
 
OP
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Objectivist01

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The problem is the when i use the tweeter on another circuit it sound very airy and clean, but on this crossover it sounds very muddy like i hear very rolled off mid tones than real treble. I had not tried upgrading the cap. But previously on a similar speaker the manufacturer had told me that the inductor can be at fault after running loud (driven to clipping) for some time. I was having a hard time believing that the inductor can go wrong than a capacitor but I replaced it on that model and it worked. This is the same series of speakers, just one model up. But the crossover point is slightly different due to a different tweeter used. Also on the previous one it was 5uF instead of 5.6uF. The resistance is ok, as I checked the rings and value and they match. Now the problem is the inductor do not have a sticker mentioning it’s specs. I don’t have a measuring device but I used a normal measuring rillet and it’s almost half of a millimeter. Not sure if it’s also 0.71mm. SoI measured the resistance from the other working speaker and it is 0.9ohm. So I looked upon the chart a found that 0.47mH inductance matching the same dc resistance having 0.5mm thickness. But as per design spec of crossover point, 0.27 mh should be the inductor when I used online calculators. So I am confused if I need to buy all and give it a try.
 

solderdude

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Just replace the capacitor with a similar value one (difference will be small) and the inductor as per instructions above and maybe even the resistor.
A resistor may, in specific overload situations, have gotten a higher resistance than indicated.
When you don't use 'audiophool' type components this shouldn't have to cost that much.
 

Wombat

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I'd just put it in series with a known(measured) resistance, say around 5 or 10ohms, and measure - good soldered or mechanical connection. Subtract the known resistance value . Voila. Close enough in this case.
 
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fineMen

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... sound very airy and clean, but .... So I am confused if I need to buy all and give it a try.
It is very likely that an inductor of value X, air-core, with the same wire thickness will have the same DC resistance. This is because such devices get optimized to the best geometry for the lowest DC resistance given the cost of the wire.

Anyway, don't be too picky. If the x-over operation would depend on the DC-R so much it is a bad design. You may end up with 0,1..0,2dB of a difference max. But change the two in your stereo set for good measure. What comes first: stop-over thinking this. Such a paranoia is going to spoil your fun with the music way way way more than the neglegible--if any, change in tonality.
 
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