This is a tutorial on how to make a very simple speaker. It only needs 3 parts to work. As a bonus, there is no soldering or hot glue needed.

Step 1: Materials

30AWG Wire - Keep it on the spool.
Headphone Jack - I used an MP3 Player auxiliary cable.
Thin Magnet - I used one that is commonly sold as a pair of "Rattlesnake Eggs."
Optional - Alligator clips to make holding the wires together a little easier. I will be using these in this guide but it'll work just as well without them.

Step 2: Splice the Audio Cable

Cut the audio cable and isolate the red and blue wires. Depending on the brand, the colors may be different. It may take a little experimenting to get the right ones.
Once you have found the right wires, strip the ends by scraping them with a razor or singing it off with a lighter. Trim the unused wires away as they may cause interference with the circuit.
If you are using alligator clips, you can hook them up to the wires to make attaching them easier.

Find the start and end of the wire spool. The beauty of this is that the coil is already made.
Strip the wires and attach the headphone jack to them. One wire to each end.

Simply put the magnet into the center hole and you are done.
To use it, just plug the audio jack into your computer. It may not work on phones.
Hold the speaker by the magnet and put it to your ear, as if you are using a 1920's telephone. Adjust the position of the magnet to experiment with sound quality. It works best with rock music as this is a very weak magnet and anything soft may be hard to hear.