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Old 5th January 2013, 09:28 AM   #1
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Default Power Inductors

Hi, I did a research on this topic but did not find too much. So sorry if I am touching an overspoken topic.

I am working in a 3 way crossover feeding a 600W-8Ohm for middles and lows. I was doing some fast numbers and I realised that the power coils will need a 12AWG gauge wire, if it is not correct I will appreciate some help.
This kind of wire will be expensive and hard to work, so i was thinking about using a 14 o 15 gauge which I can find easier and use two conductors in parallel to deal with the current needs.

I have no idea if that could be done, if anyone has dealed with this before and could give me some hints about the construction of this coil, I will appreciate!
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Old 5th January 2013, 10:59 AM   #2
Johno is offline Johno  Australia
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Parallel wound coils suffer because the inter-winding distances become variable. That is the distances between turns in the same layer and the distance between turns in adjacent layers is not consistent and the magnetic coupling between turns reduces.

Therefore for a given inductance you will need many (I am guessing 15-20%) more turns. Means the resistance goes up and the amount and cost of copper goes up and you end up no better off, or at least have diminishing returns.

As it happens I am currently winding big crossover coils with 2mm wire. Not practical to do it by hand so I have had to build a winding machine. Essentially a frame strong enough to hold the 30kg feed spool, a feed tension controller (a 2.2mm hole in a block of wood) and home made bobbins on a threaded rod turned by a car wind-screen wiper motor assembly from the scrap yard. An 18 volt DC supply with a pulse width controller to vary the speed cobbled from bits and pieces in the workshop. Biggest problem was finding a turn counter, ended up getting one from Hong Kong on ebay.

Has more than enough torque to pull the wire though and I simply guide the lay of each turn. For the first coil I thought I could varnish the completed unit but this has not been so successful therefore spay on varnish with each layer. I use nylon cheeks with a release agent on the base of each bobbin.
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Old 7th January 2013, 12:49 PM   #3
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Thank you for the info Johno. So far I found lots of info about equivalent gauge wiring and twistting effects and so on.

Anyway, the guy interested in the crossovers thinks that more than 150$ for a three way, second order, 1000W crossover is unaceptable. It seems he is not looking for quality but for cheap stuff.
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Old 7th January 2013, 11:09 PM   #4
Johno is offline Johno  Australia
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That will buy 16awg and old, used electrolytics.

You might consider a tri-amp setup with cheap and nasty plate amps?
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Old 8th January 2013, 12:33 AM   #5
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Quote:
Originally Posted by Pentodo View Post
...
I am working in a 3 way crossover feeding a 600W-8Ohm for middles and lows. I was doing some fast numbers and I realised that the power coils will need a 12AWG gauge wire, if it is not correct I will appreciate some help.
If you go to the Erse website they show power on their coils that make things easy.
Johno, a picture would be the best (of your set-up) for my mind's eye.
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Old 29th January 2013, 10:01 PM   #6
Johno is offline Johno  Australia
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Quote:
Originally Posted by Inductor View Post
Johno, a picture would be the best (of your set-up) for my mind's eye.
Here is the coil winder, the 20mH coil and the just finished speaker.
Attached Images
File Type: jpg CoilWinder2.jpg (222.2 KB, 47 views)
File Type: jpg Coil.jpg (208.5 KB, 43 views)
File Type: jpg Rear.jpg (367.3 KB, 43 views)
File Type: jpg Front.jpg (366.5 KB, 39 views)
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