A speaker converts electrical energy into audible sound waves. These sound waves are created using a complex device made of metal, magnets, wire, plastic and paper. The vibrations are created by an electrical signal changing the strength of a speaker's rear magnet, thus causing a paper or plastic cone to create sound waves by vibrating.
The speaker frame is usually made from stamped iron or aluminum. The purpose of the frame is to support all of the internal components of the speaker.
The permanent magnet is part of the apparatus that converts the electrical signal into mechanical sound waves. The permanent magnet interacts with the voice coil--which is, in reality, an electromagnet--to cause the speaker cone to move and vibrate. The permanent magnet is attached to the speaker frame. Permanent magnets are made by fusing iron oxide and strontium with a ceramic binder in a mold. The mold is then heated to melt the mixture to create a ceramic magnet.
The voice coil is an electromagnet. Its magnetic strength varies depending on the strength of the signal input. As the signal strength varies, the difference in magnetic strength between the coil and permanent magnet causes the cone and surround to move forward and backward.
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The surround is the speaker component that surrounds the cone. It is used to attach the cone to the speaker frame, while allowing free motion of the cone to create sound waves. The surround is often attached to a flexible foam buffer before being attached to the frame. The buffer allows more range of motion for the creation of lower frequency sound waves. Surrounds can be made of a variety of materials, including paper, mylar and plastic. Because of its availability and low cost, most surrounds are made of paper.
The cone is the part of the speaker that produces the sound waves. Cones can be made of many materials, including paper, mylar and plastic. Most cones are made of paper, with other materials being popular on higher-end speakers. One end of the voice coil is attached to the cone. As an electrical current passes through the voice coil, its interaction with the permanent magnet moves the cone forward and backward to create sound waves.
Once manufactured, the speaker is mounted in an enclosure. The materials and shape of the enclosure emphasize and balance the audio characteristics of the speaker for a wide range of audio uses.