Ok, wire arrived, tests are concluded.
I ordered 0,3mm (~28 gauge) enameled copper wire. From that, I would 3 coils:
2x 20 windings, ~13m, 3,2Ω each
1x 8 windings, ~5m, 1,6Ω
The first tests were with the Hero. It needs to be at max volume, which means that it outputs 2,5V.
- only the 8x coil, so 1,6Ω. The Hero put out 1,4A, so ~4W total. The sound was very quiet.
- only the 20x coil, so 3,2Ω. The Hero put out 0,6-0,8A, so ~2W total. The sound was very quiet too, but possibly slightly better than the 8x coil. Not sure, both very hard to hear.
- both 20x coils parallel, so 1,6Ω total. The Hero put out 1,4A, so ~4W total. The sound was basically imperceptible.
I wanted to test this theory with that configuration.
2 wires in parallel is a lot less that “many”, but since the result with 2 parallel coils was so much worse than just one, even though the amperage was double, i am not convinced that this approach is usable here.
- 8x coil and 20x coil parallell, so ~1Ω total. The Hero put out 2,6A, so ~6,5W total. Best result by far, but still fairly quiet.
I also still had this other 50W amp, so i tested that too. With the 20x coil i got 2,5A at 7V, so 17,5W. Volume was quite good, almost at a usable level. The wire got seriously hot though. I couldnt test the 8x coil, its 1,6Ω resistance was to low.
What i gather from this is:
Amperage is king. Volume definetly scales with amperage and thus inversely with resistance. Thats quite logical, the magnetic field strength (not sure if thats the word, not a native speaker) scales linearly with amperage. My guess is that we will need around 5A to get a decent volume. That unfortunately also means heat.
Not quite sure how voltage plays into this.On the 50W amp, as you turn up the volume, voltage and amperage go up equally. So maybe more voltage = more better? I only have 2 points of data that are not independant from the amperage, so i cant really draw any conclusions. @Satur9 , what is your opinion on this?
The number of windings also seems to positively impact volume. I need to order thicker wire to get a coil with more windings, but at the same resistance. But since we are working with AC here, more windings also increase the reactance (never heard that word before, i mean the imaginary part of the resistance) which again means lower current? Just guessing, feel free to correct me.
In the end, i believe it all comes down to power, which is annoying, because power means bigger electronics, faster battery drain, more heat etc. The “coil around the neck”-tests just constantly show that it is impractical. As much as i want to get it to work, I dont see how. Any ideas on how to proceed?