loud speaker

thingiverse

Create a small copper wire coil of about 1-2 meters, with 20-30 turns for your loudspeaker. Opt for Neodym magnets, each 6mm long and 20mm in diameter. For the audio source, attach a connector with a 3.5mm diameter to your speaker, using your mobile phone as the sound input; although it may not be very powerful, you should still hear some audible music.