Inductors made to order?

[tcpip]

Hi all,

Do you have any source who will build air-core inductors to order if I specify the mH (or uH) value and the gauge of wire (16 SWG preferred)? Corrson used to do this, but now I am not aware of anyone else.

I have a couple of sources in Bombay who will take mechanical dimensions and wind the coils, but I will have to give them the inner diameter, coil length, and number of turns. When I get such coils done, I have to spend an hour unwinding and measuring them, because they are never accurate -- the winding chaps do not use an LCR meter.

So, do you know of anyone, preferably in Bombay, who will wind based on a value, or someone elsewhere who will do this and ship the coils to me?

 

[Hari Iyer]

Hi all,

Do you have any source who will build air-core inductors to order if I specify the mH (or uH) value and the gauge of wire (16 SWG preferred)? Corrson used to do this, but now I am not aware of anyone else.

I have a couple of sources in Bombay who will take mechanical dimensions and wind the coils, but I will have to give them the inner diameter, coil length, and number of turns. When I get such coils done, I have to spend an hour unwinding and measuring them, because they are never accurate -- the winding chaps do not use an LCR meter.

So, do you know of anyone, preferably in Bombay, who will wind based on a value, or someone elsewhere who will do this and ship the coils to me?

Check out Barry,s inductance simulator where you can simulate an air core inductor by giving the inputs of inner dia, length, wire guage and by adjusting the outer dia the inductnce alue is simulated. You will require to install Java run time version for this simulator.
there is typically a mismatch of around 5% to 10% from simulated and actual value mosly due to dimension of bobbin and winding process that needs to be corrected for by measuring wirh an LCR meter.
You can get the coils wound at LR at Mumbai with any guy winding transformers as the winding method and machine are the same, but you will need to carry round bobbins with you as they usually keep only rectangular bobbins meant for transformers.
If you need them measured after winding, then you can come to my home for an LCR meter.

 

[tcpip]

You can get the coils wound at LR at Mumbai with any guy winding transformers as the winding method and machine are the same, but you will need to carry round bobbins with you as they usually keep only rectangular bobbins meant for transformers.

Thanks a lot for the help, and specially for the offer of borrowing your LCR meter. I have till now managed my measurements using an impedance jig with Speaker Workshop, and using its "measure passive component" feature. That's how I also do my 1% matching of capacitors.

Actually, the path you have suggested is rich with options, and I've done things that way for the Asawari Mark II. I was getting tired of the post-production step of unwinding and measuring, so I wanted to know whether anyone will do the coils with an LCR meter and measure accurately (I like 2% errors, max). Apparently diyaudiocart.com will do custom inductors, so I'll contact them. I'll have to pay extra for the shipping costs, of course.

 

[ketansethi1987]

They specialise in making crossovers in Delhi

Acg Networks Business enquiry form

 

[t.antony]

This is the DIY jig I used to wind my coils, Not expensive or difficult to build.

I used Bary's Inductor simulator and it's reasonably accurate.
Here are couple of coils wound using this jig.

More details on these posts.

http://www.hifivision.com/diy/14433...udspeaker-philips-fullrange-2.html#post200012
http://www.hifivision.com/diy/14433...udspeaker-philips-fullrange-3.html#post200344
http://www.hifivision.com/diy/14433...udspeaker-philips-fullrange-7.html#post215239

 

[koushik]

So, do you know of anyone, preferably in Bombay, who will wind based on a value, or someone elsewhere who will do this and ship the coils to me?

Not exactly in Bombay but ..
Recently I have got mine build by Bibin (diyaudiocart.com). I got it in reasonable price and I am sure Bibin will help you on this.

The inductors were of very good quality. The wire insulation was quite thick.

 

[koushik]

This is the DIY jig I used to wind my coils, Not expensive or difficult to build.

That is a great jig Antony :thumbsup:

 

[Hari Iyer]

Excellent jig, winding machines around the same size or smaller are available to purchase at less than 10k in Mumbai, i am not buying because of space constraint and qty of inductors i will require for my projects.

 

[tcpip]

Thanks, all. Antony, I'd seen earlier posts about your jig, and it's really tempting. I'm trying to avoid having to wind my own. I'm lazy, did I tell you?

I'm in touch with Bibin too, and he's quite supportive, but we're checking how large we can go. I may need to go up to 5-6 mH with air-core (I've done 3mH for the Asawari II), and he's checking whether he can make them. If he can, one problem will be over.

 

[Mano]

This is the DIY jig I used to wind my coils, Not expensive or difficult to build.

I used Bary's Inductor simulator and it's reasonably accurate.
Here are couple of coils wound using this jig.

More details on these posts.

http://www.hifivision.com/diy/14433...udspeaker-philips-fullrange-2.html#post200012
http://www.hifivision.com/diy/14433...udspeaker-philips-fullrange-3.html#post200344
http://www.hifivision.com/diy/14433...udspeaker-philips-fullrange-7.html#post215239

Great fixture and good innovation.

Cheers

 

[Hari Iyer]

I have calculated to as much as 1% accuracy with rectangular bobbins using the Barry simulator. This uses a corelation function between circular and rectangular bobbins. The solution is in excel with inputs from Simulator.

 

[t.antony]

... I may need to go up to 5-6 mH with air-core (I've done 3mH for the Asawari II), and he's checking whether he can make them. If he can, one problem will be over.

The DCR of my 6mH inductor was about 1.3ohms and it weighed close to 500grams. I used 19SWG but 16SWG would be a better choice.

 

[Hari Iyer]

The DCR of my 6mH inductor was about 1.3ohms and it weighed close to 500grams. I used 19SWG but 16SWG would be a better choice.

Choice of using a 19, 18 or 16 SWG will depend upon your cross-over and its not always that 16 SWG is better than 20 SWG, some time you would want to use the wire resistance to attenuate some part of the signal depending upon the driver response. A simulation of the cross-over with the driver response will give an exact guage required for the inductor.

 

[t.antony]

Choice of using a 19, 18 or 16 SWG will depend upon your cross-over and its not always that 16 SWG is better than 20 SWG, some time you would want to use the wire resistance to attenuate some part of the signal depending upon the driver response. A simulation of the cross-over with the driver response will give an exact guage required for the inductor.

My POV was different for that suggestion: why change driver's damping unnecessarily? But I did not elaborate it though .

I believe the OP also had his reasons to favour 16SWG.

 

[tcpip]

My POV was different for that suggestion: why change driver's damping unnecessarily? But I did not elaborate it though .

I believe the OP also had his reasons to favour 16SWG.

I agree that wherever there is a series resistor in the path of the inductor, there one can use a thinner gauge, save money, and tweak the series resistor value to compensate. This is a problem only where you want the full power to go through the driver without any attenuation, and your crossover circuit therefore does not have any resistors in series.

I had used 16 SWG for my inductors purely because I thought i would like to see if I can get them made with that gauge. I was facing problems finding a good guy to make inductors for me, so I went for thicker wire "to be safe" and get the job done. I could easily have used 20 SWG for the tweeter inductor, if I had added its DCR in the crossover simulation. But I did not bother -- no good technical reason.

The woofer low-pass inductors are usually large, which means you wish you could use thinner gauge and save money, but they are also usually the place where you don't want series resistance because your crossover circuit tells you that series resistances will just waste power and drop the damping factor.

 

[tcpip]

The DCR of my 6mH inductor was about 1.3ohms and it weighed close to 500grams. I used 19SWG but 16SWG would be a better choice.

I believe that when the gauge drops by three, i.e. when the wire is thicker by 3 SWG, the area of the wire doubles. So, moving from your 19 SWG to 16 SWG would have increased the weight to a kilogram per coil. That would be serious He-Man stuff. One would have to worry about how to mount such coils securely. :sad:

 

[kanwar]

The woofer low-pass inductors are usually large, which means you wish you could use thinner gauge and save money, but they are also usually the place where you don't want series resistance because your crossover circuit tells you that series resistances will just waste power and drop the damping factor.

I never prefer passive XO's for this very reason, not only they mess with the damping factor available from the amplifier's end, but also the interaction of back EMF combined from XO inductor + voice coil [i.e. reactive energy] distorting the phase response, that is the reason you have phase distortion, power loss and also current slew limitations when passive XOs are involved.

 

[keith_correa]

Another source for x-over components - theaudiocrafts

 

[jls001]

Another source for x-over components - theaudiocrafts

Their prices are quite high, though

 

[bijinmb]

Sharing the images of sample inductor build for testing purpose.

After winding and tying is done, just varnished to prevent further shaking/loosening of the winding's.

.15mH on 14AWG, Air Core





1mH on 14AWG, Ferrite Core





.58mH on 18AWG, Air Core