Solo Cup Speakers

Did you know you can make speakers out of almost anything? In this Instructable, we'll take the ever popular solo cup and show you how you can turn them into audio speakers!

Materials needed: 2 Solo or Plastic Cups, 30 gauge magnet wire, 2 neodymium magnets (P/N DCC), auxiliary cord.

Tools needed: Soldering iron, glue, drill press (optional), table saw (optional).

The first step to making your own speakers is to create a coil of wire, one for each speaker. These coils can be easy to make. We found that 30 gauge magnet wire (available here), works best. Knowing we wanted the resistance to be about 4 Ohms, we figured out that a 1" diameter coil with 147 turns would get us that!

We simply took a marker that was about 1" in diameter and started coiling the wire around it, 147 times! Make sure to keep some extra wire out at both ends as you'll need to solder this wire to the auxiliary cord. Keep the coil as tight as you can, as this will produce some better sound. We ended up putting a little bit of tape around our wires to keep them tight.

Once you have the coils made, you can solder the coils and auxiliary cord wires together. If you cut the aux cord open, you'll see it has 3 wires, positive, negative, and ground. The wires represent the left and right speakers, and the share a common ground. Since both speakers should be ground, we spliced the ground so both speakers have ground.

If using the magnet wire, be sure to sand the insulation off to get a good connection.

Once you have soldered all the wires together, you can glue the coils to the back of the cups! This is a quick, easy step, but it is important.

Be a little generous with the glue...if you get glue on the coil, that's not a bad thing! That can help hold the coils together to produce a better sound. Coils are often dipped in wax to keep them together.

The stand design we went with is pretty simple. We took a thin piece of particle board, traced the diameter of the solo cups, and used a forstner drill bit to drill out a big hole. Make sure the hole will be slightly smaller than the cup diameter.

After we drilled the holes for the speakers, we simply took a 2x4 and cut a slot in it using the table saw. This would be the base piece to hold the speakers upright.

That's it! It really is that simple! Insert the solo cup speakers into the holes you drilled and plug it into a MP3 player. To play it safe, we use an older MP3 player...we don't want to risk plugging in into our phones just yet!

You'll notice that you don't hear any sound until you place the magnet into the coil. Something awesome with the magnet happens here and it produces sound...pretty decent sound at that! You can simply just hold the magnets in place with tape and it'll keep producing sound!

We chose to use a magnet size that was just smaller than the coil diameter, so the magnet could sit inside of the coil nicely. We've also found that cylinders tend to work better, as they have a bigger magnetic field than a disc.

Watch the video to hear how the speakers sound. Also included is a decibel level chart, showing that the speakers get pretty loud! With the decibel meter right near the speakers, the highest level it reaches is about 92 dB, which is considered "Very Loud and potentially dangerous" on a decibel level chart!

In the chart, as the time goes on, the speakers were moved to 12" away from the decibel meter, which describes the sudden drop in levels. The levels it drops to are safer for your ears! It also depends on the song you're playing...as you can tell, there were some breaks in our song where the levels drop!

We tested out some smaller magnets too, and you do see a little bit of a difference. With smaller magnets, less sound in produced.

First we have to ask, what is sound?

Sound is a vibration in the air. Waves of changing pressure in the air move your eardrum, allowing you to hear sound. Just like ripples in a lake where you throw a stone, ripples in the air are what makes sound. For a simple example, consider banging a drum. After hitting the drum, the surface vibrates back and forth, pushing the air in waves. When those sounds hit our ear, we hear noise.

If the vibration is slow, we hear a low pitch. If the vibration is fast, we hear a higher pitch. So, to make a speaker all we have to do is drive a surface (often a cone shape) back and forth. The movement of the speaker makes waves of pressure in the air -- sound!

Next we have to look at Motive Force - What Drives a Speaker?

A pair of magnets can stick together. We're going to use this basic property of magnets to move our speaker. We use one permanent magnet and one electromagnet.

Permanent Magnet - An object that produces a persistent magnetic field. Neodymium magnets are a great example.

Electromagnet - An electric current running through a coil of insulated wire generates a magnetic field. While the current flows, it acts much like a permanent magnet. If no current is flowing, it stops acting like a magnet.

The permanent magnet is always on. The electromagnet we turn on and off by running current through it, or not. The interaction between the magnetic field of the electromagnet (the coil) and the neodymium magnet is what creates the movement in the speaker.