Most people understand that speakers produce sound, but they usually don't know exactly how these devices work to produce the sounds we hear and enjoy. Through the creative use of electrical current and magnets, speakers are able to produce the range of noises that make up our favourite songs and movies.
Speakers and the Human Ear
The human ear is a complex organ that translates fluctuations in air pressure caused by vibration and movement into sound. These vibrations generate kinetic energy to surrounding air particles, just like how movement in water generates waves. The word "frequency" is used to describe the length of the waves created to generate sound - the faster the vibration, the higher the frequency.
The human ear is capable of hearing frequencies from 20Hz to 20,000Hz. Low-frequency sounds are often perceived as deep or low notes (bass), while high-frequency sounds are perceived as high-pitched notes (treble). Mid-frequencies are often known as "midrange". Speakers work to replicate these sounds in the highest quality possible, depending on the overall construction and materials used to build the speaker.
How Speakers Work
The three basic components of any speaker is the cone, the electromagnet and the permanent magnet. The first task of any speaker is to translate the electrical signal it receives from a source into audible sound. The electromagnet, a metal coil that generates a magnetic field when exposed to electrical current, allows it to do just that. The electromagnet operates similarly to a permanent magnet, except that reversing the current's direction within the coil also reverses the poles of the magnet.
Positioned behind the electromagnet is a fixed permanent magnet. The direction of the magnetic field changes rapidly as pulses of electrical current pass through the electromagnet. This causes the electromagnet to become attracted and repelled from the permanent magnet at rapid rates, creating vibrations. To make sure that the electromagnet moves strictly up and down, nearly all speaker systems use a spider and surround-style suspension system to hold the cone and electromagnet in place. The suspensions behave as springs to bring both components back to their original positions.
The cone, a device made from paper, plastic or composite materials, amplifies the vibrations generated by the electromagnet. As a result, sound waves are created that eventually reach your ears, thus allowing you to hear your favourite music. All three components are housed within a metal chassis - the chassis itself is usually encased in a specially-built box that's normally constructed from wood and other materials.
There are plenty of specialised speakers, also known as "drivers," that focus on generating a certain range of frequencies. Woofers, midrange speakers, tweeters and sub-woofers are four main types of specialised speakers. Woofers are large speakers that focus on generating sound at low frequencies. Tweeters, which are usually much smaller in construction, specialise in reproducing high-frequency sounds. Midrange speakers focus mainly on generating midrange frequencies, as their namesake suggests.
Sub-woofers are unique, as they replicate sounds at tremendously low frequencies. These frequencies can even be low enough for the human ear to not be able to hear, but enough for people to feel. Sub-woofers generate subtle shakes and rumbling, thereby adding a unique dimension to the listening experience.