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Old 22nd August 2009, 03:51 AM   #1
speedie is offline speedie  Australia
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Location: palmyra fremantle western australia
Default diy inductors

Fello fanatics
I would like some input re inductor winding I am at present putting together a 7.1 av system, I have designed the speakers using bass box pro and xo calculator the towers are in a mtm format which has a bass driver in the lower dived section it is to crossover at 240hz
According to the calculated inductor from xo pro I need to wind a coil of awg 16# at 5.5mh this is a large component that would offer some resisentce of flow to the speakers, I would also assume that there would be a decrease in efficiency (db)
That aside has anyone had any success in producing there own coils
I spent approximately four hours yesterday winding and have fabricated 10 coils
The hardest part of this process is getting the wire to feed onto the bobbin evenly and to keep count at the same time
I also noticed that if they are no wound tightly enough there is a lot of differential in meter readings, after some time I managed to get good results but I still had to unwind wire to get back to the desired mh readings
I will mention that if I zipped tied them really tightly together, the meter readings would increase which is probably why we pay so much for the perfect lay inductors
I had to pick up some more wire to day and was talking with the owner of the rewind business I mentioned re problems with inconsistency in readings and he said to me why don’t you wind so far then use the alligator clips on your meter to scratch into the varnish and take a reading that way you will not use so much wire up by having to trim each time you wind just a light spray of varnish to cover your scratches and away you go (tricks of the trade)
Has any one used two pack glue to secure the coils once they have finished winding as it takes a lot of cable ties to secure my coils?
Has anyone fabricated the impedance equalization circuits that are suggested in xo pro software as these can become very expensive when you add up all of the bipolar caps, inductors and resistors necessary to complete the circuit, I was considering building the main crossover then adding the equalization circuits after to see if there is any audible difference as I am not privee to expensive metering equipment
has any one taken readings with there own diys then replaced with factory wound items,was there any noticable in/decrease in proformance!
Any input would be greatly appreciated
Cheers to more beers Speedie
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Old 24th August 2009, 12:30 PM   #2
speedie is offline speedie  Australia
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It would appear that no one has taken any interest in responding to some of my questions
I am sure that someone in this vast community would be thinking on similar lines
Thanks again
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Old 24th August 2009, 12:43 PM   #3
foo is offline foo  Tibet
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Cause most ppl would rather buy from existing suppliers.
Unless you are going to make silver inductors, it's not worth the time and enegy.
However, if you are going to make silver inductors, it would be more cost efficient to use active crossover.
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Old 24th August 2009, 01:04 PM   #4
Glowbug is offline Glowbug  United States
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I know people who wound their own inductors for ham radio projects, but it does seem like a PITA.
The machine does not isolate us from the great problems of nature but plunges us more deeply into them. - Antoine de Saint-Exupéry
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Old 24th August 2009, 01:14 PM   #5
infinia is offline infinia  United States
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For inductors larger than 1.5mH or so, I consider using transformer I (eye)lamination's, should reduce Rdc and copper by heaps. Look at commercial offerings for ideas here. Sources can be a problem for most unless your re-winder has contacts.
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Old 24th August 2009, 01:20 PM   #6
Conrad Hoffman is offline Conrad Hoffman  United States
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Man, what's the diy world coming to? Lots of speaker builders wind their own inductors with fine success. I usually use cable ties, but have potted some smaller inductors in epoxy. Works fine. I don't worry about the couple feet of wire lost when used to trim the value. In the grand scheme of things it's not much, and I find other uses for it. To keep track of winding I built a winding fixture. This is nothing more than a flat plate that supports a block running a shaft. It has a crank on one end (that would be me) turning a crank, and a Jacobs drill chuck on the other. You put whatever form or arbor in the chuck and crank away. Now, the useful part is that I mounted a Veeder-Root counter on top so I don't have to count turns. Even better, it's the style that goes forward and backwards, so it keeps track as I unwind and fiddle around with Mylar tape when winding things like pot core inductors and transformers. To gild the lily, I put a fold out piece of sheet aluminum on one corner that has some stabilizing grooves filed in. This provides a nice place to scrape the enamel off the ends of the inductor wire.
I may be barking up the wrong tree, but at least I'm barking!
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Old 24th August 2009, 01:26 PM   #7
AndrewT is offline AndrewT  Scotland
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try to organise a mechanical turns counter. The number of turns is absolutely critical.
Soak the assembled coil in hot varnish.
Expels most of the air.
Vacuum impregnation would be even better but I think that's more difficult.
regards Andrew T.
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Old 24th August 2009, 04:45 PM   #8
Magura is offline Magura  Denmark
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Speedie, do a search, and you'll find your questions has been answered already.

If you add my name in the search, it may make the search even easier, as I have explained the ins and outs of inductor winding at length.

Everything is possible....to do the impossible just takes a little while longer.
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Old 24th August 2009, 08:05 PM   #9
AMV8 is offline AMV8  United Kingdom
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I make all my own inductors and have done for a long time.
I use an Avo LCR meter to check the inductance.
I have made air cored and solid cored inductors and never had a problem. I have not found it that important to add the turns precisely. I usually set them in glue when completed.
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Old 24th August 2009, 08:16 PM   #10
wg_ski is offline wg_ski  United States
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Originally Posted by AMV8 View Post
I have not found it that important to add the turns precisely.
Only if you can measure the final result. If you have to go strictly by calculations you need to keep precise track of it.

Let's see here.... average cost of inductors -$20. Cost of a home-brew special $2. DMM that measured inductance (as well as everything else) - $100. How many inductors before it pays for itself?
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