We've previously covered how to make a speaker from earbuds and paper cups. If you don't have a pair of donor earbuds handy or want to learn how to build basic speakers from scratch you can do so with a few key electronic components and a paper cup.
Instructables user Guiciwoochi made this basic speaker by creating a copper wire coil using a magnet, making a cardboard bracket to hold the magnet, placing that bracket inside the paper cup, and taping the copper wire coil to the outside of the cup. Solder the two ends of the copper wire coil to the headphone jack wires, and make a cover for the speaker using cardboard and paper to elevate the cup so you can maximise reverberations. Check out the source link below for full step-by-step photos and detailed instructions.
It won't be an extremely loud speaker, but it should work fine for listening to music from your phone or computer.
How to Make Paper Speakers From Scratch [Instructables]