| Magnets [message #75550] |
Sun, 17 February 2013 21:59  |
Sonicsound
Messages: 59
Registered: July 2012
Location: United States
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Baron |
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When I was a kid, my father would always dissect broken things and save some of the parts. One thing that I remember is how he would always save the magnets in speakers. I never thought to ask, until now when I am making a homemade compass, why are there magnets in speakers? What purpose do magnets have in sound?
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| Re: Magnets [message #75573 is a reply to message #75568] |
Wed, 20 February 2013 09:33  |
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Wayne Parham
Messages: 18787
Registered: January 2001
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Illuminati (33rd Degree) |
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Actually, a speaker transforms electrical energy to kinetic energy using the interaction of two magnets. One is a fixed magnet and the other is an electromagnet. Back several years ago, they used to make speakers with two electromagnets, one that was energized with a stable direct current, and the other fed the audio signal, which is an alternating current waveform. In either case - field oil or fixed magnet - the result is the same, which is that the audio signal causes movement of the cone because of the interaction of the fixed magnet with the one fed with the audio signal. Your "HowStuffWorks" link shows this pretty well.
What you described is the reverse, and that's pretty much how microphones work. The sound moves the diaphragm, and that in turn moves the coil. The magnet flux cuts across the moving coil and this creates a current, which is the audio signal.
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I remember my dad explaining speakers and mics to me as a kid and I guess I got the two mixed up! That was also the same conversation where he explained the purpose of magnets in generators and alternators in cars... (I was absolutely fascinated by magnets as a kid.)
