Find your answer here -
http://en.wikipedia.org/wiki/Loudspeaker
http://electronics.howstuffworks.com/speaker.htm
2007-02-02 04:44:46
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answer #1
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answered by Anonymous
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Hello mate...heres why and how magnets are used...
The traditional design includes a lightweight semi-rigid cone, a coil of fine wire (usually copper), a circular magnet, and a rigid support structure.
The coil (known as the voice coil) is attached to the apex of the cone. A "gap" is a small circular hole, slot or groove which allows the voice coil and cone to move back and forth. The coil is oriented coaxially inside the gap. The gap is established between a permanent magnet and a center post (a.k.a. "pole-piece"). The center post and back-plate are sometimes a single piece called the "yoke". The gap is where the magnetic field is most concentrated. One magnetic pole is outside the coil, whilst the other is inside the voice coil. In addition to these components, a dynamic speaker also includes a suspension system to keep the coil centered and to make the speaker components return to a neutral point after moving. A typical suspension system includes the spider (a.k.a. "damper"), which is at the apex of the cone, often of "concertina" form; and the surround (a.k.a. "bellows"), which is usually made of rubber and affixed at the outer circumference of the cone. The parts are held together by a chassis or basket (a.k.a "frame"). When an electrical signal is applied, a magnetic field is induced by the electric current in the coil which becomes an electromagnet.
The coil and the permanent magnet interact magnetically, generating a force which causes the coil and a semi-rigid cone (diaphragm) to move back and forth and so reproduce sound at the frequency of the applied electrical signal. When a multi-frequency signal is applied, the complex vibration results in reproduction of the applied signal as an audio signal.
Driver cones may be constructed of a variety of materials, including paper, metal, various polypropylenes, and kevlar. Baskets must be designed in order to preserve rigidity and are typically cast or stamped metal, although injection-molded plastic baskets are becoming much more common in recent years, especially for inexpensive drivers. The size and type of magnets also differ depending on design goals. Sometimes, but not always, larger and more powerful magnets are associated with higher quality speakers. Tweeters are subject to a very different set of variables and parameters; their design and construction is extremely variable.
Despite marketing claims, lighter and more rigid cones do not always sound better. The weight and internal damping of the cone in a dynamic speaker should be appropriate for the characteristics of the rest of the driver, and the intended enclosure, in order to produce accurate sound.
The cross-section image shows the construction of a speaker using an overhung coil. This term is used when the coil's height is greater than the gap's, and this construction is the most commonly used for the magnetic force on the voice coil remains the same throughout the voice coil's maximum range of motion. This construction attempts to keep the number of windings within the gap (and hence the force experienced by the coil) constant, as the coil moves back and forth.
Cut-away view of a dynamic loudspeaker. The lead wires as shown are for illustration purposes. Commonly the voice coil wires are soldered to the lead wires and the soldered joints are glued to the diaphragm, close to the dust-cap periphery.
Cut-away view of a dynamic loudspeaker. The lead wires as shown are for illustration purposes. Commonly the voice coil wires are soldered to the lead wires and the soldered joints are glued to the diaphragm, close to the dust-cap periphery.
The other common construction is the underhung type. Here, the voice coil's height is smaller than the gap's. This construction attempts to keep the magnetic flux constant across the coil as it moves back and forth (this also results in the coil experiencing a constant force). However, the linear motion region is considerably reduced for any given magnet size.
Both methods try to achieve the same thing — a linear force on the coil, and each has its pros and cons. The overhung design offers softer or gradual non-linearity (compression) when the coil starts exceeding the Xmax limits. Speakers using overhung coils have better efficiency and power handling. The underhung design offers greater linearity within the Xmax limits but as the coil starts exceeding Xmax limits the non-linearity (and hence distortion) rapidly increases. This design also requires a more powerful magnet, and so speakers using underhung coils tend to be less economic, or less efficient. For this and other reasons, the vast majority of dynamic speaker drivers sold today are of the overhung type. [3]. Xmax is the maximum linear peak-to-peak travel of the voice coil. This means that the displacement of the voice coil is a linear function of the input voltage within the limits specified by Xmax.
2007-02-05 21:49:37
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answer #2
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answered by Anonymous
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permanent magnets are used in speakers , It is used to create the movement of the coil and the cone which produces the sound
2007-02-05 00:37:51
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answer #3
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answered by judy 1
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it helps in creating different vibrations in the diaphragm of the speakers and generate sound out of the signals received from the music system...
2007-02-02 12:34:12
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answer #4
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answered by Harish Jharia 7
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