Every speaker converting a electrical signal from amplifier to mechanical air movement. To do this with high fidelity and acceptable efficiency a speaker have to placed in a suitable loudspeaker eclosure. The size of the enclosure dependent on the lowest frequencies to be reproduced. So the woofer enclosure is much larger than required for midrange and high frequencies.
Here are the basic elements of the speaker:
It is made of pressed sheet metal, cast aluminum, plastic or fiberglass. Cast baskets have higher strength, so they are used at high loads. It is used for mounting and centering elements and to facilitate mounting in box.
In addition to the important feature is the stiffness of the shaping, so that the air and the sound output from the rear part of the cone and encountered the least resistance.
It is made of ferrite, low-cost magnetic material. But also they use expensive alloys with higher induction values, such as alni (alnico), or neodymium. Generally, the bigger the magnet, the greater the efficiency of the speaker and the enhanced reproduction of pulses.
Inside the magnet is an air gap and a core pole. At the slot of the reel and moves it should be as narrow as possible. Pole body part of the magnet is located inside the moving coil. At its end it has called compact coil, or the copper ring, which prevents the growth of impedance with increasing frequency.
This is wound on a carcass wire (approximately 10 m), a copper or aluminum, with circular, rectangular, square or hexagonal. Wire with a circular cross-section is the cheapest and poorly dissipates heat.
Speaker diaphragm has two suspensions. The one, called surround, that we often see this suspension of the cone. It is designed to keep the membrane as possible constant coefficient of elasticity of the entire range of the move. As a rule, is made of rubber, foam (now very rarely used), coated fabric or the same material as the cone.
The second suspension (inside, under cone), called spider, is designed to keep the carcass coil centered in the air gap. It, like a surround, has a big influence on the resonance frequency Fs and the speaker cone excursion Xmax. As the material is used impregnated fabric, generally light brown or yellow colour. The speakers adapted for heavy loads are mounted two such spiders.
This part of the most characteristic in the construction of the speaker and the most visible. Its task is to push the air (to be exact - air molecules located in its vicinity, in both front and rear).
It must meet two basic requirements: to be light and rigid. Since the beginning of its construction uses paper with long fibers. In addition to it can be polypropylene, kevlar, rigid foam, aluminum and combinations of these materials to form a so-called a sandwich structure (multilayer).
Most often it produces paper polypropylene coated cones, becouse they are cheap, as far as lightweight and suppressing the resonances.
Usually in the form of a dome, always at the center of the cone. On the one hand it protects the element from contamination, and the second pushes (or pulls) the excess heat from the magnetic system. The material used here include paper, fabric, plastic or aluminum.
Sometimes dust cap is made in shape phase plug. The difference is that the true equalizer is stationary, because attached to the pole, and imitation is moving, which can be checked by pressing cone gently with your finger.
The speaker as an independent signal converter has a very low efficiency, because the sound waves generated by the diaphragm from the front and rear cancel each other. So speakers placed appropriately performed, and a suitable enclosure. Apart from him, inside are a crossover, damping material (such as glass wool, wool, or synthetic fiber batting,) and wires. On the rear baffle terminal is mounted to connect with amplifier.
The cabinet of the speaker are usually made of wood, good quality MDF or chipboard of high density, hardness and strength. To strengthen construction (to prevent vibration and avoid resonance) inside of the larger box bracing is mounted connect opposite walls.
Types of enclosures:
- sealed (closed)
- ported (bass reflex)
- with passive radiator
- with transmission line
More information: https://en.wikipedia.org/wiki/Loudspeaker