Cheaper to buy or make decent inductors.

I was talking to a friend that makes his own speakers and he told me that the price of cross over inductors has almost doubled in the last few years. I told him It wouldnt be that difficult to make his own but i couldnt tell him if or how much he could save by doing this. Not sure exactly what type he buys but their good quality air core with out being exotics. (not flat or litz or silver wire etc.). Can anyone tell me if there is any economic reason ( if my time is cheap but still worth something and I dont need to buy any equipment (hand wound) ) to make your own inductors?
 

benb

Member
2010-04-24 1:52 am
It seems economical enough to me - the main parts cost is in the magnet wire. On the other hand, with a premade coil you're only buying as much wire as it takes to wind the coil with none left onver. But if you make many coils that's not much of a problem. Also, with making your own, you can make each coil the exact value you want, instead of ordering the closest value commercially available.

I prefer having an inductance meter (I have a B&K 878 RLC meter, a couple hundred dollars, good to at least 1 percent), but winding formulas you find online or in most any year of the the ARRL Handbook are generally pretty accurate. Also, with a variable frequency sinewave generator and an ac voltmeter (most any DMM) you can drive the inductor in series with a resistor, sweep the frequency until the voltage across each is the same, solve the inductive reactance formula for inductance and plug in the frequency and resistor values.
 

bob91343

Member
2010-03-11 10:43 pm
Making inductors is easy. The problem comes when you get the parts. You can't generally buy, say, 10 feet of wire - you gotta buy a spool. Cores not so bad but when you add in the shipping it's not so economical.

I enjoy making inductors. I have several spools of magnet wire and don't mind making air core coils. I have wound many transformers too. The nice thing is you get to design it and make whatever you choose, not what happens to be a standard unit. Measuring is easy for me, as I have a couple of nice bridges.
 
I know that there is software out there that will use your computer's sound card to generate sine waves, then via a bit of electronic gizmo, feed that back into the sound card where it's analyzed. This software lets you test T-S parameters of woofers, values for inductors and capacitors, etc.

I forgot where I found it. Jeez... come to think of it, would come in handy now.

You can use it to create your own inductors, accurate to at least 1% or better.

I check ebay now and then to see who's selling magnet wire for how much, and considering the prices you can get it at in bulk it's definitely a savings if you make your own inductors.

Also, there are a few websites you can find that have calculators which will tell you to pretty good accuracy how many turns of what average diameter you will need for a specific gauge to create a certain value.

I used to buy perfect layer wound stuff at retail prices but have since then been "rolling my own."
 
I've sometimes overwound or rewound existing inductors to get higher inductance values than are normally available, all the way up to 100mH.

For a future 'ultimate' speaker project, I have some 12AWG heavy build square magnet wire that I plan to use for some air core inductors as part of a LP filter. Square magnet wire effectively allows a gauge heavier wire to be wound in a given cross sectional area compared to a round magnet wire.