Tweeters and Woofers

If you observe carefully, you may notice that in most loudspeakers, particularly as they get larger than little portable boom boxes, you can see more than one speaker driver-usually a smaller diameter one atop a larger one.

These speakers have two sizes of speaker driver: tweeters above and woofers below

There are several reasons why speakers use multiple drivers in different sizes. While it is true that a single driver can cover almost all the audible spectrum by itself, there are a number of limitations it runs up against. If the driver is small it can't move much air and will struggle to generate bass at a useful level.

Larger drivers can move more air, but the problem is that speakers become more directional as the frequencies they are reproducing go up. This is known as beaming.

As frequency increases, the associated wavelength decreases; speaker drivers usually start beaming at a frequency with a wavelength equal to the diameter of the radiating cone. This means you`ll only hear the higher frequencies if you`re right on axis with the speaker. It doesn`t make for a balanced sound or a good speaker. The simple solution is to use different sizes of drivers with each one tailored to reproducing a specific range of frequencies-different parts of the audible spectrum (bass and treble, or bass, middle, treble).

This concept works in tandem with a frequency dividing network in the speaker box called a crossover. A crossover delegates the right frequency range to each driver type: tweeters for the highs and woofers for the lows.

You don't need to know the science behind speakers to be able to listen to and enjoy them. But if you intend to spend serious dough on audio equipment, it`s always a good idea to first equip yourself with some knowledge. A little base knowledge will help you understand why certain design decisions were made, how they influence the sound, and to help you identify snake oil salesmen.