# Inductor specs



## bizbad (May 11, 2010)

I am building a crossover and found the proper size .3 mh and the proper wire gauge inductor but the resistance value is supposed to be .2 ohms and what I have is .3. Will a tenth of an ohm cause any problems?


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## Anthony (Oct 5, 2006)

Which section of the crossover is this in? If it's for a low power portion (tweeter section, notch filter, etc), you can just inline a resistor to match it up.

For the woofer section, this may not make a difference, but you may want to measure/listen before worrying about any remediation strategies. My gut says no (for the woofer section), but every situation is different (more efficient speakers, high order crossover, etc).

What project is this for?


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## lcaillo (May 2, 2006)

What are you using to determine this value? Are you measuring or are you going by the specs?


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## Anthony (Oct 5, 2006)

Sorry, I read that backwards. I thought it was supposed to be 0.3 Ohms and you got 0.2 Ohms, not the other way around.

Not possible to add negative resistance in this case :doh:

Leonard is right, you may want to measure it to make sure. It might be closer to what you need anyway, despite what the label says.

The gauge that is specified is usually just to help get the resistance correct. If you are getting too much resistance, the only other alternative is to go up a gauge to lower the resistance. It would be more important to get the Ohm rating correct than to use the "indicated" gauge.

Edit:
Found this at Parts Express:
http://www.parts-express.com/pe/pshowdetl.cfm?PartNumber=255-218&DID=7
0.3mH and 0.26Ohms. A little closer. It's 18 gauge.

They also sell 14 and 15 gauge inductors, but you may have to unwind a little to get the impedance right (and they'd be under the recommended resistance).

Good luck.


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## lsiberian (Mar 24, 2009)

Anthony said:


> Sorry, I read that backwards. I thought it was supposed to be 0.3 Ohms and you got 0.2 Ohms, not the other way around.
> 
> Not possible to add negative resistance in this case :doh:
> 
> ...


That would be close enough for your needs.


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## bizbad (May 11, 2010)

This is for the tweeter section on a Zaph bamtm. I followed his list from Madisound. I just happened to notice yesterday that the spec listed on the one inductor is .1 ohm higher than he said it was in his list.


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## Anthony (Oct 5, 2006)

If you don't get into a philosophical debate with him, Zaph is pretty cool about helping out with real issues with his designs. He gets a lot of "can I swap these drivers and still have it sound good questions". He ignores those.

However, your questions may just be a simple typo. It's worth an e-mail directly. He also (used to) frequent diyaudio.net forums. However you get the info, please share here in case someone else runs into this problem.

Worst case, go with a lower resistance inductor and wire a resistor in series to get the proper spec. Tweeters don't usually handle that much power, so the 10W or 20W varieties would be fine. But the nice thing about crossover tweaking is that most of the speaker is built. Just use wire nuts to swap components in and out until you get the voicing you like and then solder it together.

Good luck.


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## bizbad (May 11, 2010)

Maybe I will email him and see. It's worth a shot.


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## bizbad (May 11, 2010)

Well it seems he has no email listed there anymore. Just an email faq list. I was thinking about the circuit for the crossover though. It seems to me that because there is a 7 ohm resistor before it with a + - 5% tolerance, thats makes a .35ohm variance acceptable for the resistor. So in theory .1 of an ohm farther down the line shouldn't matter.


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## Be_Mo_Mods (Feb 14, 2010)

you will be fine with what you have. If you still have doubts PM me and I can give you some links to guys who are building those. They might have more info for you.

Bobby


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