Thought I should upload a better thread about winding coils on your own. I use a DIY lexan jig and various notched hubs or PVC/ABS rings to do this.
I posted images and instructions last in my Pangolins thread on page 4 of the previous MAC forum:
I’ll link the last thread with the recent bifilar coils here, so they aren’t missed:
Recently, I pondered a likely typo on US-Coils website about their XQ coils supposedly having ferrous cores. I procured 2 kinds of Ferrite rings from Amazon to play around with and see.
Due to standard sizing of these ferrite rings,
I had to make a couple new notched center hubs to fit inside these cores, basically a 0.5” and 1” thick for single and double stacks.
I wound the first coil on the rounder ferrite core, single thick with 18awg. (Not pictured) I only gained 0.1ohm reduction in DCR. Further testing will be done.
I wound the second on a double stack of the more square ferrite rings. This time I glued them together and used 16awg. Comparing the 16awg bobbinless air cores I wound initially for my Wanlü, the air core 2.75mH are 0.7 ohms. The ferrite cored coil has a DCR of about 0.5 ohms. That’s not a bad advantage. More testing will come.
I measured the bass range of the Wanlu with both the original air core and this ferrite-ring-cored alternative. I figured an HD sweep would tell me if it was saturating or adding any coloration to the woofer’s output by comparison. These were made at the same power input level, so you can see there is a fraction of output gain for the Ferrite over the naught, though easier to see around 100Hz:
Other than that, I see nothing that would show it is being overloaded at this output where other Ferrite coil types have already started to saturate in others’ efforts to test them.
I know I have not posted the HD further up in frequency, but they did not differ that much over their range of use.
I bought these from All Electronics (closed), or a buyout at PE. They should be available lots of places. Sometimes, I even use the label maker instead of my Sharpie.
Total napkin Calc here, but say I use the newly found yellow core at less than $10. The spool of wire cost me $105 shipped for 10#.
Us Coils charges about $32 for a 2.7mH/16awg coil. Using the DCR as a length approximation, being at 0.5 vs 0.64 ohms, the 78% comes to $25 before the 9 buck core for a retail cost of $34.
If we go on Madisound cost at 2.5mH is $41, I’m saving about 7-10 bucks retail.
Then you figure winding these coils is much less than 33% of the spool cost.
This is why I do 16awg coils over 14awg. I used a 5# spool of 14awg once to see. I got 10 coils out of it, 2x 0.47, 2x 1.5, 2x 0.9, 2x 0.33, and 2x 0.1mH. That’s it, no more, no less. The smaller the gauge, the more I save per coil.
I came across this 11awg “hand coil”, and 100’ length was an option, so I ordered a pair. $112 shipped for both. I was optimistic after running an online calculator to see what inductance I could achieve.
I used these slightly larger $12 ferrite ring cores in hopes I could increase the inductance value a bit more:
Just as a reference, I then looked up a coil of similar specs.
12/10awg:
Splitting the difference in cost to estimate 11awg and adding a little for value achieved, roughly $100CAD looks like a valid retail cost, or roughly $72USD plus shipping. 56 + 13 = $69 my cost plus my labor.
Here is the result:
An 11awg 1.35mH coil with a DCR of 0.06 ohms for 69 bucks. Mine physically is 1.125" thick, and 4.75" diameter, the 10awg is 1" x 4", likely without zip tie thickness. Mine would also be 1" without them added. My diameter is referenced to a larger initial core size. Saved on plausible tariffs and extra shipping costs, and cut DCR considerably over the next size larger gauge.
I still have yet to wind the other one. This is the largest coil I’ve wound yet, even larger than the multitap 6.0mH 16awg I made awhile ago. It also barely fit within my newer smaller lexan winding jig. To the point of how large, I had to use a plastic putty knife to wedge the lexan wheels from the coil and snake zip ties through due to being beyond the tie slots.
Was it worth it? I guess I’ll have to wait and see the results of using them in the future vs a similar value coil. Let me also say I was hoping for twice the resulting value.
That is getting up to the size of the power transformer in a medium sized amplifier.