Q: What are the parts of a speaker?

The Anatomy of a Driver

You know what the outside of a typical loudspeaker looks like. You might also have seen a speaker without its grille (the covering, usually made of a cloth material, that hides the parts). Here's a closer look at the nitty-gritty, which you might not be acquainted with unless you've built your own speakers. Aperion Audio speaker engineer Ken Humphreys provides the details. You'll be quizzed later.

The cone is what pushes the air and begins the sound wave's journey. Most modern tweeters move air with a dome rather than a cone. The electromagnet that drives the cone is a voice coil. A magnet provides the nonchanging magnetic field that allows the voice coil's alternating magnetic force to be attracted or repelled. The top plate, back plate and pole piece are the magnetically conductive parts that concentrate the magnet's energy around the voice coil. The spider in this case isn't an eight-legged insect but a springy cloth disc that keeps the voice coil and bottom of the cone from moving to the side but that allows forward and backward movement. A surround is a springy ring that keeps the top of the cone from moving to the side while allowing it to move forward and backward. Combined with the spider, a suspension system is formed for the parts that move (the cone and voice coil). Electricity from the amplifier connects to the voice coil via flex wires and wire terminals.

To keep debris from entering the gap between the magnet and the pole piece where the voice coil resides, a dust cap is glued to the cone. Finally, another method of adhesion, the frame (or basket) holds all these parts together.

So how does it all work? The voice coil is an electromagnetic engine whose north and south poles are determined by the way it is charged. Charge it one way, and the coil moves up. Charge it the opposite way, and the coil moves down. Place the coil near a permanent magnet, and, by alternating the charge, it will either be attracted to or repelled from the magnet. Attach this coil to a cone so that you can push some air around, hook it up to an amplifier with an alternating audio signal, and, presto, you have a speaker (without the cabinet and crossover).