How do speakers make sound?

Inside a typical speaker, a coil of wire called the voice coil sits in the field of a permanent magnet and is attached to a cone or diaphragm. The audio signal is an alternating electric current, which makes the coil an electromagnet whose polarity changes rapidly. The coil is pushed and pulled by the permanent magnet, moving the cone back and forth in step with the signal. These vibrations compress and stretch the air, creating sound waves that reach your ears. Large woofers handle low frequencies, while small tweeters reproduce high ones.