I have done it experimentally but it's way too slow/tedious for production .
With my kludged/home setup I mean.
I had a sliding collar turned, think "a piece of pipe", slightly oversize (a tenth of a mm larger) so it could slide along the mandrel and former.
Its edge provides a perpendicular "wall" or "shoulder" against which flat(tened) wire can rest on edge.
Otherwise it's impossible because it's an inherently unstable position.
Same as expecting an LP or food platter to stay on edge by its own.
Even worse, being pulled hard in all directions while being wound.
I started the first turn carefully by pushing wire with my thumbnail against that edge, then each new turn against the previous one.
Very slow, it can fall against one side at any moment, a mess.
A machine can be designed to do that automatically of course, here it was only an experiment.
Round wire has none of those problems, that's why a flat wire coil can cost 10-20X what a round wire one does.
In my book, not worth it 🤷🏻
Fine for large Companies who are centered on top of the top speakers, of course, such as JBL or EV or ALTEC.
And even so ...
With my kludged/home setup I mean.
I had a sliding collar turned, think "a piece of pipe", slightly oversize (a tenth of a mm larger) so it could slide along the mandrel and former.
Its edge provides a perpendicular "wall" or "shoulder" against which flat(tened) wire can rest on edge.
Otherwise it's impossible because it's an inherently unstable position.
Same as expecting an LP or food platter to stay on edge by its own.
Even worse, being pulled hard in all directions while being wound.
I started the first turn carefully by pushing wire with my thumbnail against that edge, then each new turn against the previous one.
Very slow, it can fall against one side at any moment, a mess.
A machine can be designed to do that automatically of course, here it was only an experiment.
Round wire has none of those problems, that's why a flat wire coil can cost 10-20X what a round wire one does.
In my book, not worth it 🤷🏻
Fine for large Companies who are centered on top of the top speakers, of course, such as JBL or EV or ALTEC.
And even so ...
DIY winding sounds like a great opportunity to wind a feedback coil for motional feedback on top of the normal voice coil.
Feedback coil would need many more turns (since it needs to generate an adequate S/N voltage to feed back to the amp) but can be very fine wire (since you aren't powering the driver).
If you ask any questions about this post, it is unlikely I'll have the technical moxie to answer any, but somebody else might.
Ben
Feedback coil would need many more turns (since it needs to generate an adequate S/N voltage to feed back to the amp) but can be very fine wire (since you aren't powering the driver).
If you ask any questions about this post, it is unlikely I'll have the technical moxie to answer any, but somebody else might.
Ben
I've done a few inside/outside wound coils on that very same winder from Amazon. You just need to practice with it.
For a typical 2 layer VC, the trick is to keep the tension very even and smooth, so the final coil diameter is uniform after the first layer. The second layer isn't as critical but you still need to be consistent. I use specific diameter Alu mandrels I have turned in a lathe to exact size, which are coated with Teflon spray before the VC former is laid down first. You need to leave a separating gap in the former to account for thermal expansion. If the gap isn't there, the former will butt up at higher VC temp and go out of round on you.
There is always some reduction in final diameter when the VC is removed from the mandrel. That exact amount of reduction is what you need to achieve every time so the VC fits perfectly in the gap. You have to allow for thermal expansion, especially with Alu formers. Kapton is more forgiving.
I use a high temp epoxy to adhere the windings and apply a light final surface coating. Its then baked at 100 deg C for a few min and let cool slowly. This keeps the whole assy from deforming out of round. It also allows the former to relax and stay round after removing the mandrel.
Also, use the highest temp enamel wire and epoxy you can get. This way the VC will handle a decent amount of temp abuse. They make heat conducting epoxy to further raise power handling. You can get fancy and de-gas the finished VC before baking it in a vacuum chamber. This is what I do with larger VCs and crossover inductors.
For a typical 2 layer VC, the trick is to keep the tension very even and smooth, so the final coil diameter is uniform after the first layer. The second layer isn't as critical but you still need to be consistent. I use specific diameter Alu mandrels I have turned in a lathe to exact size, which are coated with Teflon spray before the VC former is laid down first. You need to leave a separating gap in the former to account for thermal expansion. If the gap isn't there, the former will butt up at higher VC temp and go out of round on you.
There is always some reduction in final diameter when the VC is removed from the mandrel. That exact amount of reduction is what you need to achieve every time so the VC fits perfectly in the gap. You have to allow for thermal expansion, especially with Alu formers. Kapton is more forgiving.
I use a high temp epoxy to adhere the windings and apply a light final surface coating. Its then baked at 100 deg C for a few min and let cool slowly. This keeps the whole assy from deforming out of round. It also allows the former to relax and stay round after removing the mandrel.
Also, use the highest temp enamel wire and epoxy you can get. This way the VC will handle a decent amount of temp abuse. They make heat conducting epoxy to further raise power handling. You can get fancy and de-gas the finished VC before baking it in a vacuum chamber. This is what I do with larger VCs and crossover inductors.
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