Inductor design/construction - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 25 Old 01-04-08, 11:14 PM Thread Starter
drf
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Re: Inductor design/construction

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Awesome job on the coils and your jig! BTW, didn't mean to steal your thunder by posting the calc link.
Thank you, It's cool about the thunder thing, As far as I am concerned the more people who post links and opinions the better it is for everyone.

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As I price the larger air coil inductors in the $20-35 and higher range and consider the prospect of buying numerous inductors for several upcoming speaker builds, this starts to make sense for the adventurous soul.
It cost me less to build the coil winder and build the 4 inductors needed to make 2 2nd order XO's than it would have cost me to buy 2 1st order crossovers pre-built. So I get the advantage of the xo's being custom and cheaper.
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I wonder if adding a crank handle to the wheel of your coil winding lathe could make the process a bit easier and serve as an index to help keep track of the turn count. And if you were going to do more than just a couple inductors, I bet a turn counter could be added to the rig.
I should have shown the this pic earlier then:
Inductor design/construction-handle.jpg

I already have plans (schematics) for a turn counter but didn't want to overcomplicate this thread. maybe if people get enthusiastic about it I'll do a turn counter mod thread or something.
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post #12 of 25 Old 01-04-08, 11:47 PM
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Re: Inductor design/construction

Out of curiousity, do you have any premade inductors you could measure to compare the homebuilts too?


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post #13 of 25 Old 01-05-08, 01:25 AM Thread Starter
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Re: Inductor design/construction

Not at the moment, and to be honest I didn't even think about comparing I just thought testing would tell all. If I can I will try and pick one up this week and do some electrical tests side by side as well as in the XO.
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post #14 of 25 Old 02-09-08, 01:29 AM Thread Starter
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Re: Inductor design/construction

Well I still havn't got one of the shelf for comparison, unfortunately getting to the shops is very low on my current list of priorities. But just to let people know I still intend to do the comparisons I just need to sort out a few issues first.
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post #15 of 25 Old 02-09-08, 07:25 AM
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Re: Inductor design/construction

Take your time. Family first -- inductors can wait.

Best of luck.
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post #16 of 25 Old 03-04-08, 06:05 PM
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Re: Inductor design/construction

I think you may want to check your inductances with an LCR meter. MCM has a basic Tenma LCR meter on sale for $39.95. I just got one.
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post #17 of 25 Old 05-16-08, 02:44 AM Thread Starter
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Re: Inductor design/construction

Well I finally got around to taking measurements of one of the test inductors I made and it measured at 240uH. Thats 11% tolerance on the 272uH I needed. Hopefully I will find enough time to post some more detail. And some photos. I will also try to make a direct (measured and tested) comparison to some off-the shelf inductors.

But I may need to make some more as I am rather happy with the ones I made earlier inside the speakers and don't want to disturb them.

Cheers
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post #18 of 25 Old 05-18-08, 03:30 AM
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Re: Inductor design/construction

I've tried unwinding inductors from Jaycar to get desired value. what a nightmare when you find you have unwound too much and have to wind it back on, or worse still have to rejoin the wire!! I would welcome this DIY as long as it is fairly accurate.
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post #19 of 25 Old 05-18-08, 04:30 AM Thread Starter
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Re: Inductor design/construction

The ones I have done using the above method produce inductors with a 10% tolerance (11% for my first attempt). We can get the tolerances tighter by simply cutting the copper longer and throwing on a few more turns (or a few less) as needed before finishing off. However one question that remains is how important is it for the inductor to be precise? Using the test inductor I made, assuming the driver impedance is 4 ohms then the crossover freq' will be 2338Hz for the 272uH inductor, however the actual inductor is 240uH therefore the freq' will actually be 2650Hz. Is this difference enough to upset your design? I some cases it will and in others it will probably make no perceptable difference. Some people reccomend a 5% tolerance maximum, this is quite achievable in diy without much effort. To be quite honest if you want more accuracy than this you should probably be looking at a fully active system .
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post #20 of 25 Old 05-19-08, 01:40 AM
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Re: Inductor design/construction

DRF
I wasn't having a go at you or your home made inductors. I think its great. And you are probably right about not needing 100% accuracy. My comment comes about because: after i adjust an inductor or make one myself I have no equipment to measure its inductance value. I have to trust in the value that i guestimated and then inert it into a crossover and measure the measure frequency response. primitive i know. but its what you do when you have no measrement equipment. I plan on purchasing some multimeters and that wt3 woofertester in future.
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