Sound is created by waves that are created by vibrations in the air. Those vibrations get processed by tiny hair-like follicles on our ear and ear drum until we hear sound. How are these vibrations made in headphones? First there are three key components: a magnet, a voice coil, and a diaphragm. From the audio source, the electrical current will travel through the wire until it reaches the voice coil. In the voice coil there is a magnet that creates a magnetic field that will allow the voice coil to vibrate once the current reaches it. Due to the magnetic field, the alternating current that is coursing through the wire causes the wire to gain and switch polarities, which leads to the vibration of the voice coil. That eventually turns into sound waves that we can hear.The voice coil is attached to the diaphragm, so the vibrations that the voice coil is making will be directed to a certain point (in this case your ears) to create sound. We will be showing you step by step how to create this process on your own.
Step 1: Materials:
(1) Electrical Tape
(1) Copper wire (28-gauge)
(1) marker with a diameter of 1.5 cm
(2) neodymium magnets (15mm diameter)
(4) ceramic magnets (12mm diameter)
(2) 2oz plastic cups
(1) 3” x 4” Sand Paper
(1) 7” x 11” paper towel
(1) Hot glue gun
(9) Pipe cleaners
A roll of masking tape
(1) Aux plug
A roll of duct tape
Step 2: Voice Coil Assembly:
- Connect the hot glue gun to power source.
- Measure 2 pieces of 2 ½ m of copper wire and cut them.
- Sand 20.5 cm off both sides of the end of the two copper wires.
- **Note: It is important to sand the wires that you will be making connections with because the red paint is an insulator that acts as a resistor. If the wire was not sanded then the oxide surrounding the copper wire will slow down the electrical current and affect the production of sound.
- **Note: 28 gauge wire was chosen because it is thin enough to coil, and it has enough resistance for the device to function. For example, a wire with a 38 gauge will be thinner and will have a greater resistance output, and a 10 gauge wire will be thicker and it'll have less resistance. 28 gauge wire was chosen because it's not too thick nor too thin, and its resistance was not too great or too small.
- Set that aside. Then, wrap electrical tape with the sticky side up around the marker.
- **Note: Electrical tape was chosen to cover the wire instead of masking tape or any other tape because it is resistant to electricity.
- Press one end of the sanded copper wire to the very edge of the electrical tape and begin wrapping the copper wire clockwise around the electrical tape. Make sure that the coils are not overlapping and are tightly packed next each other.
- Continue wrapping the wire around the marker until there are 35 coils.
- 35 coils were chosen because while prototyping the design of the headphones it concluded that out of the three trials that consisted of 10 coils, 25 coils, and 35 coils the 35 coil trial worked best in the production of sound.It produced a clearer sound with identifiable lyrics as opposed to the static that the other trials generated.
- Repeat steps (3-7) for the second voice coil
- **Note: The voice coil is one of the three main components in any speaker. The current that is flowing through the wires, once they're connected to a power source, will turn the wires magnetic. Once they're magnetic, they will attract and or repel other wires that are magnetic as well (they will also attract / repel magnets). Therefore, the magnetic field generated will get stronger when the wires are coiled together. The more coils there are the stronger the magnetic field will be. The Alternating Current that is flowing through the wires is going to flip the polarity of the voice coil. The second main component in a speaker is the magnet. The magnets are not going to going to vibrate because they're permanent (won't switch polarities) and because they have more mass than the voice coil. The attraction and repelling of the voice coil polarities and magnets will cause the voice coil to vibrate. This is important because vibrations are the source of all sound waves. In this case, vibrations means having sound.
Step 3: Assembly of Ear Set:
- Once the two coils are complete, twist one of the sanded ends of the first voice coil to one of the sanded ends of the second voice coil so that they are wrapped together in parallel.
- Grab a ceramic magnet and place it inside the cup and grab a neodymium magnet and place it on the bottom side of the cup.
- **Note: Ceramic magnets were used because we couldn't purchase anymore neodymium magnets. There does not have to be a mixture of both types of magnets. As long as there are a total of 6 magnets being used, the headset should work fine. Also, the project could be done with 2 magnets (one for each ear); however, with the addition of more magnets the sound became clearer and slightly louder.
- The magnets will be attracted to each other, so there is no need to glue them in place.
- After this, place another ceramic magnet on top of the neodymium magnet.
- Now, grab the first voice coil and place it over the neodymium and ceramic magnet. It should fit perfectly over them and it should not slip off.
- **Note: The magnetic field is stronger in the center of the coil because the alternating current is rotating around and through the wire. Therefore, when there are a set of coils there will be a stronger magnetic field that is rotating around and through the center of the voice coil. Hence the magnetic field being stronger in the center of the coil.
- Repeat steps (2-6) for the second voice coil and cut.
- Thread the sanded end of the wire through one of the aux plug's terminals. Twist the wire until it is secure.
- Repeat step 8 for the other sanded end of the wire.
Step 4: Attachment of Diaphragm:
- Place both cups on top of paper towel.
- Grab a pencil and trace around the edges of the cup.
- Remove both cups from the paper towel and cut out the circular shapes.
- Grab the glue gun and place a ring of hot glue around the top of both cups.
- Grab one of the circular cut outs and carefully align it with the edges of the cup.
- Place it on top of the hot glue.
- Repeat steps (5-6) for the other cup.
- **Note: The diaphragm is the third main component in a speaker. It receives the vibrations generated by the voice coil and the magnet and then amplifies them. This is what creates the loudness of the sound being heard. The paper towel was chosen for the diaphragm because it gave the best results in terms of loudness out of the three materials that were tested. Other materials that were tested during the prototyping phase were aluminum foil and card stock. The paper towel produced the best results, because it is lightweight and thin, so the sound waves were able to move the diaphragm back and forth very easily. Therefore, amplifying the sound waves more effectively when compared to the performance of the foil and card stock.
Step 5: (Optional) Aesthetic Assembly of the Headset:
- Get three pieces of electrical tape. Each piece has to be the length of the exposed wires.
- Cover each wire with the tape and fold the excess tape over.
- Make sure the tape is tightly around the wire.
- Cut off the excess tape. Be very careful not to cut the wire.
- Get three pipe cleaners (any color).
- Wrap these pipe cleaners around the two wires that are connected to the aux plug. Be careful not to bend the wires too much.
- With the extra exposed wire attached to the cup, wrap two pipe cleaners around each one on both sides until there is no wire exposed.
- Leave the top twisted wire alone.
- Attach the top twisted wire to a headband on the side that touches your head.
- Once the wire is on the headband, tape it on with masking tape until it is secure and unnoticeable.
- **Optional: Paint the masking tape the color of the headband.
- To attach the headband to the headphones, place a small amount, the size of a dime, of hot glue by the rim of the cup on the side that will touch the headband.
- Press the headband against the hot glue of the cup until the glue dries.
- Repeat steps 12 and 13 for the other headphone.
- To cover the coil and magnets, place duct tape (with any design/pattern) around the red cup and on top of the vice coil until the entire setup is covered in tape.
Step 6: Troubleshooting:
If sound is not produced, here are some things that need to be checked:
- Check the wires that are connected to the Aux plug and make sure that they are connected in the same fashion that the wires in the above photo are.
- Make sure that the two wires are not touching. This will cause the headphones to emit a static-like noise.
- Make sure that none of the voice coils on either ear are overlapping.
- Check the entire headset for a broken connection. If one is found, either solder the broken connection together or sand the broken wires and wrap them together.