Inside a speaker are a number of drivers, which are charged with the task of producing the actual sound you hear. These are usually a cone, behind which is a â€˜voice coilâ€™ and magnet that electrically make the cone move back and forth to create air pressure. Theyâ€™re mounted on a â€˜baffleâ€™ â€“ a flat panel at the front of the speaker enclosure.
Because one type of driver canâ€™t reproduce the entire range of frequencies that can be heard by the human ear, different drivers are employed to handle different frequency ranges. These different drivers are called a woofer, midrange and tweeter. The woofer is designed to reproduce sounds towards the lower end of the spectrum, but not necessarily to the same depth as a subwoofer â€“ usually down to about 80Hz. The midrange driver obviously reproduces midrange frequencies, covering from around 200Hz up to 3000Hz, while the tweeter tackles high frequency sounds typically from 2,000Hz up to 20,000Hz.
A crossover (or filter network) is used to separate the incoming signal into those different bands and send them to the right driver. Speakers are often described by the number of different bands the signal is split into â€“ for example a two-way design splits the sound into two bands, which are typically reproduced by a woofer and a tweeter. A three-way speaker might include a woofer, midrange and tweeter.
However, a two-way speaker may actually sport more than two drivers (two woofers and two tweeters, for example), but the sound is still only split into two bands, so the multiple drivers all reproduce the same sound. These drivers can also be arranged in various ways, which affect how the sound reaches your ears.
Full range drivers, meanwhile, can reproduce a wider frequency range and are employed when thereâ€™s no room for multiple drivers â€“ many cheap all-in-one system speakers go down this route.
Other things you may come across when gazing at a speakerâ€™s spec sheet include sensitivity, which describes how efficient the speaker is at reproducing sounds and is expressed in dB, and impedance, which describes how much power the receiver has to provide to drive a speaker â€“ the lower the impedance (measured in Ohm), the harder it is to drive.