I know nothing about electrics. I am learning some very basics by making a pair of incredibly simple headphones with a 3.5mm jack, some enameled wire, some magnets, and some paper cups.

After a bunch of trial and error, I have figured out how to connect it all so that sound comes out of both cups (this was a huge victory for me haha!)

I now just have a few questions about the coil and how it affects the volume.

  1. How does the diameter of the coils affect it?
  2. How do the number of coils of wire affect it?
  3. Does the way the coils sit on top of each other affect it? i.e., coiling it like a spring so that the coils are vertically on top of each other, versus coiling it so that each coil sits beside the previous one, so it grows out horizontally (therefore making each coil bigger than the previous one).

I know I could learn the answer to these by trial and error, but at this point I'd really like some help understanding the theory of the electromagnetic field and how the magnet interacts with it.

  • \$\begingroup\$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. \$\endgroup\$
    – Community Bot
    Dec 10, 2023 at 23:07
  • \$\begingroup\$ basically the more ampere-turns in the coil and the more magnextic field lines that intersect the coil the stronger the force will be, and thus louder.. \$\endgroup\$ Dec 11, 2023 at 0:05

1 Answer 1


You should have one year of full time math and engineering studies well done to be able to handle the all needed calculations. The needed calculations cover parts of mechanics, acoustics, electrodynamics and material strength theory. Nobody cannot write here the details. Get a book of electroacoustics.

Another approach is to disassemble an already existing loudspeaker or headphone and then rebuild it 2 times. Once by reusing old parts as much as possible and once by making as much as possible by yourself. 100 years ago it was common that most advanced hobbyists built their speaker elements or headphones at home. Even today one can order DIY kits for those items. In web you can find DIY guides for magnetic headphones, mostly planar ones.

An advanced level pre-WW2 hobby radio book probably shows how to build antique headphones. I guess it's a still manageable approach because very rare of us can cope with the tolerances needed in building modern earplug headphones. Planar headphones are in somewhere between.

This article shows some images of the mentioned antique headphones: https://www.diyaudio.com/community/threads/antique-headphones-with-moving-iron-drivers.372764/

One of the images:

enter image description here

  • \$\begingroup\$ Thank you - so is it not a straight forward answer as to how the diameter affects the volume? I.e. its not as simple as bigger diameter = louder? \$\endgroup\$
    – harpomiel
    Dec 11, 2023 at 9:26
  • \$\begingroup\$ making the coil diameter bigger without reducing the number of the turns, the AC current in the coil and the static magnetic flux density around the coil increases the magnetic force and that makes possible to move more air and faster, but how to avoid the reductions and also how to avoid increasing the moving mass too much is not at all straightforward. Make antique style headphones - they are much simpler. No moving coils are needed. The thin enough straight iron plate is a challenge. Alexander Graham Bell's telephone used just that headphone idea. Search for it. It worked also as mic. \$\endgroup\$
    – unawriter
    Dec 11, 2023 at 13:16

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