To get a good idea of the physics behind the functioning of a loudspeaker watch the video above.
youtube link here:
In short, the loudspeaker uses the interaction between the temporary magnetism generated in a coil of current carrying wire and the permanent magnetism generated by a stationary neodymium magnet.
1 Large cilindrical neodymium magnet
2 meters 0.5mm copper wire
1 plastic plate
4 business cards / playing cards
2 Aligator cables
Hot glue gun
Stereo system OR phone + sound amplifier
Step 1: Create a 2cm High Paper Cylinder
Cut a 2 cm strip along the long side of an A4 page.
Paste some paper glue along this strip.
Wind the strip up to a width just wider than your magnet.
Secure the strip with some electrical tape.
Step 2: Connect the Cylinder and a Plastic Plate With Hot Glue
Wrap up the paper cylinder with 2m of 0.5mm copper wire.
Make sure the cylinder is centered
Allow 5 minutes or more for the hot glue to dry
Use a lighter or some sand paper to strip the ends of the copper wire
Step 3: Connect Speaker to Stereo Output and Test With Magnet
Speaker should work with both polarities, one of which may work better.
If the speaker works use some blue tac to secure the magnet to the table.
Step 4: Create Some Paper Springs With Business Cards
Adjust until the speaker works well.
See it in action in this video starting around the 9 minute mark: