- Speakers come in all shapes and sizes, enabling you to listen to music on your iPod, enjoy a film at the cinema or hear a friend’s voice over the phone.
- When things shake about, or vibrate, they make the sounds we can hear in the world around us.
- Sound is invisible most of the time, but sometimes you can actually see it!
- If you thump a kettle-drum with a stick, you can see the tight drum skin moving up and down very quickly for some time afterward pumping sound waves into the air. Loudspeakers work in a similar way.
- At the front of a loudspeaker, there is a fabric, plastic, paper or lightweight metal cone (sometimes called a diaphragm) not unlike a drum skin (colored gray in our picture).
- The outer part of the cone is fastened to the outer part of the loudspeaker's circular metal rim.
- The inner part is fixed to an iron coil (sometimes called the voice coil, colored orange in the diagram) that sits just in front of a permanent magnet (sometimes called the field magnet, and colored yellow).
- When you hook up the loudspeaker to a stereo, electrical signals feed through the speaker cables (red) into the coil. This turns the coil into a temporary magnet or electromagnet.
- As the electricity flows back and forth in the cables, the electromagnet either attracts or repels the permanent magnet.
- This moves the coil back and forward, pulling and pushing the loudspeaker cone. Like a drum skin vibrating back and forth, the moving cone pumps sounds out into the air.
How to Achieve High-Fidility (Hi-Fi):
