All headphones have three essential components: the magnet, voice coil, and diaphragm. Headphones work to project sound through electromagnetism. Whenever you plug in your headphones into your phone or computer to listen to music, the audio source sends electrical signals through the wires which will reach the voice coil. Aligned at the voice coil's center is a magnet that will create magnetic field. With the magnetic field and the active electrical current being applied onto the voice coil, electromagnetism occurs. Because an electrical current runs through the voice coil, the coil becomes magnetic temporarily, and it will repel and attract to the permanent magnet located at its center. Because of the alternating current passing through the wires, the relative orientation of the poles in the electromagnetic field will switch, which leads to the voice coil's vibrations. These rapid vibrations will vibrate the air within our ear and the tiny follicles present will process the vibrations that we will distinguish as sound. (I strongly suggest making a 30-thread voice coil for the best sound quality; I've tested a 10-thread voice coil and it isn't that great.) The diaphragm's function in the headphones is to enhance sound projection. This project is geared towards all people, and can definitely be used to teach physics concepts to the young.
Step 1: Materials
(2) .9525-diameter Neodymium magnets
(2) scrap pieces of metal
(4) paper bowls
(1) Roll of 28 gauge copper wires
(1) Glue stick
(1) Small scrap piece of paper
(1) Wire cutter
(1) Aux cord 3.5 mm drive
(1) Soldering Kit
Art supplies for personalization
Step 2: Wrap Paper Around Glue Stick
Take a small scrap piece of paper and wrap around glue stick comfortably (about a millimeter). Be sure not to wrap the piece of paper too tightly, for it will be difficult to remove later on.
Step 3: Wrap & Remove Copper Wire
Tightly wrap copper wire around the piece of paper 30 times. Make sure to leave 1 inch of loose wire on each of the ends. Then, slip paper and coil of wire off the glue stick. Since this will be your voice coil, an ESSENTIAL component of the headphones, you must wrap the copper wire as perfect as possible. Once the electric current is applied and once the magnetic field is centered within the middle of the voice coil, the voice coil will vibrate rapidly. This vibration is what we will perceive as sound.
Step 4: Sanding Your Wires
Sand the two 1-inch ends with sandpaper, making sure the coating is fully removed from the ends. You will always sand the ends of each wire you'll be using in this design. The only remaining color on the ends should be of copper.
Step 5: Attaching the Magnet to the Bowl
Take one paper bowl, one scrap piece of metal, and one neodymium magnet. Place the neodymium magnet in the bottom of the bowl and the piece of metal on the outside bottom of the bowl so that the magnet stays in one place. Create a thin slit 3 millimeters around the magnet.
Step 6: Sticking Bowls Together
Take two scrap pieces of paper, roll it, then wrap tape around so that the sticky side is facing outwards. Create two of these. Then, place at the bottom on the bowl.
Step 7: Place Bowls on Top of Each Other
Take this bowl–the one you just worked with–and place it with another empty bowl. Keeping the circular cutout in place, insert the voice coil in this slit. Place tape over voice coil. Remember, coil needs space to vibrate.
Step 8: Repeat Steps for Other Headphone
Repeat Steps 1-6.
Step 9: Tie Voice Coil Wires Together
Take a long piece of wire that connects the 1-inch piece of wire (attached to a voice coil) to the other voice coil’s 1-inch piece of wire by tying them together (make sure ends are sanded). Then take a long piece of cardboard that will fit on your head–this will be your headstrap–and tape the wire to the cardboard. Reference the video at about 0:56.
Step 10: Connect Wires From Each Voice Coil to the Two Terminals of the Aux Plug
Take two long pieces of wire and tie each one to each remaining 1-inch piece of wire. Then attach the two long pieces of wires to the aux cord 3.5 mm phone plug.
Step 11: Solder All Joints
Make sure to solder all twined wire to improve conductivity.
Step 12: Troubleshooting
If you encounter problems, the source of your problem can most likely be derived from your connections. Your connections can be:
• broken/weak/not tied or soldered together well
• connections at ends where some coating is still present
• touching at the terminals (located at the aux plug)
Make sure to check your entire headphone for a faulty connection. You may want to resolder, re-sand, or re-tie your connections. Burning the ends of your connections with a lighter is another option you may use. Good luck!