Just in time for the weekend: a homebrew speaker using a plastic cup, business card, Legos, wire and a magnet.
How it works?
The coil generates a magnetic field when electricity is applied to it. The magnet attracts or repels the coil and makes it to move. The vibration generates the sound that we hear thanks to the air.
Most of today speakers have a resistance of 8 ohms. This homemade speaker may have less than 8 ohms and may not be able to make loud sounds but basically it shows exactly how it works.
Using different materials, may cause the sound to change, even to make it louder.
I’m certain that you could replace some of the bits with what you have on hand. Let us know what sort of hacks you come up with!