How speakers work

The driver contains a cone or a diaphragm which is made either of paper, plastic or metal. The narrow end of the cone is attached to a voice coil which is placed in a magnetic field created by a magnet. When currents flows through the voice coil, it becomes an electromagnet. A electromagnet can change its polar orientation depending on the flow of electrical current.

A speaker applies this fact by the use of an amplifier changing the electrical signal all the time. The negative pole of the electromagnet repels against the negative pole of the permanent magnet while the positive pole of the electromagnet attracts the negative of the permanent magnet. Thus the changes in the magnetic force push and pull the voice coil and along with it the speaker cone to produce sound.

There are a few types of speaker. The large driver woofer is between 8 to 12 inches in diameter and is responsible for reproducing low frequencies from 20 to 500 Hz. The middle sized driver called the midrange driver is about 4 inches in diameter and reproduces 200 to 4,000 Hz. The smallest driver called the tweeter is less than an inch in diameter and reproduces high frequencies from 2000 to 20,000 Hz.

Ever wonder why woofers are large while tweeters are smaller? This is because a small speaker cone is lighter and allows rapid and fast movements required to produce high frequencies. Conversely, a bigger speaker cone is heavier and movement is much slower, suitable for low frequencies.

There is a circuit in the speaker called the crossover to break the audio signal into different components and route the different frequency ranges to the respective drivers.

The drivers and the crossover are placed in the speaker enclosure. Speaker enclosure are usually made of wood and purpose is to absorb the driver's vibration.

There are different types of enclosure. Enclosures which are sealed are known as acoustic suspension enclosure. In bass reflex speakers, there is a hole in the cabinet so that no air pressure can build up due to the inward movement of the cone. The benefits include the increase in acoustic output level. Secondly, less amplifier power is required to achieve the same volume and efficiency is increased. The only problem with this design is that there is no difference in air pressure to let the driver spring back to its resting position. As a result, the bass tends to be less accurate and clear.