Important Components of a Speaker-
Magnets- The magnets provide a stationary magnetic field to oppose the alternating electromagnetic field of the voice coil which causes the voice coil and, therefore, the diaphragm to move.
Voice Coil- The voice coil directs electrical audio signal. The voice coil also provides a path for electrical current which creates and strengthens an electromagnetic field opposed by the magnet’s which causes it to move and because it is secured to the diaphragm, the diaphragm also moves.
Diaphragm- The voice coil rests on the diaphragm so when the voice coil moves, the diaphragm moves with it. The diaphragm actually amplifies the vibrations of the voice coil the diaphragm moves like a piston to pump sound waves in all directions. The diaphragm is sometimes called the cone.
- 4 neodymium magnets
- 6 meters of 28 gauge insulated copper wire
- Electrical tape
- 2 plastic cups (no more than 3 inches in height is advised) (cups with larger diameters may make give the speakers an echo effect)
- 3.5mm auxiliary audio plug
- Audio source
- Headband, hat, or anything else that can go around your head that you can attach your headphones to
We used the following materials to improve the aesthetics of our headphones. While they do not affect the sound quality, the make the final product more presentable.
- 3-D printed caps (to cover the coil)
- More electrical tape to cover the cup
- Heat shrink tubing (two sizes, one big enough to fit one wire, another that can fit two wires with heat shrunk tubing over it)
- Glue stick
- Wire cutters (optional, scissors will work fine too)
- Heat Gun or hairdryer (If you are using heat-shrink tubing)
Wrap one layer of electrical tape, sticky-side up, around the smooth top portion of an uncapped glue stick.
Cut approximately 3 meters of wire and tape on end to the side of the glue stick, leaving around 12 inches on one end so that you can easily attach it to the other headphone and your audio source.
Coil copper wire around the tape 30 times, then trim off any excess wire after measuring out, at least, an additional foot.
Remove tape and coil from glue stick and tape the coil to the electrical tape with more electrical tape, so that the coil cannot unwind.
Repeat steps 1 through 4 for a second coil.
Tape a coil to the bottom of a cup, ensuring that the tape presses the coil firmly into the base of the cup. Make sure it is centered and the two sanded ends can be easily accessed. Then place one magnet inside the coil and another inside the cup, the magnets will be attracted to one another and pin them in place.
Repeat steps 5 through 7 on the second cup.
Sand both ends of both coils and take one wire from each and twist them together. Then, with electrical tape, tape the wire along the inside of the headband, hat or whatever else you are connecting your headphones too, make sure that there is no wire visible. The headphones should hang off either end of the headband without much wire to spare. If there is too much, untwist the wire and cut it down, sand again and re-twist.
Take the other two wires and thread one through the ground of the aux plug and the other through one (or more) of the positive or audio input terminals. Screw the cover onto the aux plug and fill with hot glue, this prevents the wires from disconnecting.
Lay down a long piece of electrical tape an inch shorter than the wire from the aux plug to your headphones. Lay the two wires on the electrical tape, be sure that they are not touching and one end of the tape is flush with the aux plug. Then lay another piece of electrical tape of the same length on top and press the pieces together. Cut down the center of the tape from the end closest to the headphones, being careful not to cut the wires. This will allow you to put the headphones around your ears.
If you have access to heat shrink tubing, you can use to better insulate and secure your wires. First, find (or cut) two pieces of tubing with a very small diameter about 2 inches shorter in legnth than your wire. Thread your wires through the tubing and leave about one inch of bare wire on each end. Take your heat gun (or hairdryer) and put it on a high heat, low air setting. While making sure the wire does not move inside of the tube, heat both ends of both tubes so that they contract around the wires. (keeping them in place). You can now heat the rest of the tube until it contracts. Now, take a piece of tubing 8"-10" shorter than your wire and has a large enough diameter to fit in both pieces of shrunk tubing. Insert your already heat-shrunk wires into the tube until they are almost flush on one side. (leaving several inches of the individual wires on the other side) If your Auxiliary jack is structured similar to ours, you can position it in such a way that the tubing will hold it in place. Making sure everything is lined up correctly and there are no kinks inside the tube, slowly heat the exterior until it contracts and you can see the individual wires inside. This should provide a well-insulated cord that will be difficult to bend or break.
Step 11: Step 12: (Optional)
This STL file can be loaded into almost any 3d printing software. It can be printed without supports, but it is recommended that you use PLA with the cooling fan on 75% speed of higher.
Super glue the caps over the voice coil, on the bottom of the cups.
Test your headphones. Do they work? If not, go over the steps again to make sure that you didn't miss anything, then check the troubleshooting step if you still can't figure it out. The video shown below of our headphones playing It's a Small World is not entirely accurate as the crackle sound in the background does not actually exist but is from the microphone. We wish you good luck on you project and hope that you have just as much fun with it as we did.
Step 13: Troubleshooting
- Make sure that there are no crossed wires that will change the flow of electricity.
- If your connections are bad, you can solder the wires together instead of twisting them together.
- If the sound is of poor quality, or the volume is low, try a different cup. You want it to be rigid, do not cut a plastic cup, they lose their rigidity when you do so. Yogurt cups come in a variety of sizes and shapes.
- Double-check your sanding. Sanding removes the wire's insulation and allows electricity to flow from one sanded wire to another. If not sanded properly, you will not have sound.
-If the sound quality is still poor after trying a different cup, try adjusting the bass and treble levels on your audio source.
Step 14: Explanations of Materials
- We chose to use 30 coils of wire because, after testing 10, 20 and 30 coils on our headphones, we discovered that the greater the number of coils, the better the sound quality. We also discovered that the greater the number of coils, the softer the sound. We decided that the quality of the sound is more important than the volume, especially since the volume from a 30 coil headphone is still significantly loud. If you would like to sacrifice quality for volume, wind 20 coils for each side of your headphones instead of 30.
A stronger electromagnetic field is produced when you have a greater number of coils. Because of this stronger field, the magnet is acted on with more force. When the polarity electromagnetic field changes several thousand times per second, the magnet vibrates rapidly. If there is more force when the polarity changes, the magnet is pushed in the opposite direction with more force, and a greater amount of its inertia is depleted. The magnet does not move the diaphragm as much as it does when there are fewer coils, but it can vibrate at a faster rate (and produce higher pitched sounds). When there are fewer coils, the magnet can move more freely. If the polarity switches, there may be a small delay where the magnet keeps travelling thanks to its inertia. This pushes the diaphragm further, creating greater pressure waves, which we interpret as louder sound. Higher pitched sounds requiring very precise vibrations may sound distorted.
- We chose to use a glue stick to coil around because it is slightly larger than our neodymium magnets. You want your coil’s diameter to be as close to the magnets diameter as possible without touching it, so that the magnetic field between the magnet and coil will be stronger and produce stronger vibrations. (leading to more audible and higher quality sound).
- After testing several different diaphragms, we settled on plastic cups. We tried sheet protectors, copy paper, paper towels and the plastic cups. The sheet protector, paper towel and copy paper all were too flimsy and difficult to attach to a basket. We also chose the plastic cup because it doubles as the diaphragm and basket.
Step 15: How It Works
The voice coil vibrates because of two magnetic fields that oppose and attract each other. One is created by the neodymium magnets and the other is produced by the voice coil. The rapidly alternating current (the audio signal) switches the polarity of the coil, which causes the coil and therefore the diaphragm to move up and down, parallel to the magnet. The diaphragm moves like a piston, in and out, creating pressure waves that we interpret as sound. You can imagine it as a drum, when you hit it, it sinks and then comes back up, only the diaphragm does it much more quickly.