What are Voice Coils?
Techquickie
·Techquickie
·2017-05-06
·
1,069 words · ~5 min read
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so what's a voice coil is that one of those uh twisty cables on an older style
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telephone that you always seem to hit stuff with as you moved around the
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room no while voice coils are indeed
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coils of wire the term is typically used
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to refer to one of two things the wires
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that actuate the ARM of a hard drive or
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the wires that make your speakers go bum
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you know both of those applications benefit from the main strengths of voice
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coils extreme accuracy and high movement
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speed you see voice coils move by using
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something called the Lorent Force which is created by placing a coil of wire in
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a fixed magnetic field when current is
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put through the coil it turns into an electromagnet making it either be
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repelled or attracted to the fixed magnetic field giving you a force this
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force can actually be quite strong
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meaning that voice coils can speed up or
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slow down extremely quickly speakers for
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example can accelerate at rates in the ballpark of 800 m/s squared or 80
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G's put into context that is 16 times
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the ex acceleration required to make you lose Consciousness 27 times quicker than
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a space shuttle launch and 21 times faster than my
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Lamborghini but how exactly does that make your speakers and your microphones
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work well for a microphone as we've
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covered in more depth here there's a membrane that moves back and forth as
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sound waves hit it these vibrations are turned turned into an electrical signal
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as a coil of wire on the back of the diaphragm moves over a magnet to turn
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this electrical signal back into sound the process is reversed so the
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electrical signal goes into the coil which moves the speaker to create your
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sweet sweet beads and it's the extraordinary
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acceleration and precision that we mentioned before that makes it possible
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for speakers to produce such a wide variety of sounds on demand what about
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computer hard drives then well you can learn more about them in an upcoming
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video because we realized we haven't actually done one yet but in a nutshell
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on one side of the ARM that hovers over
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the spinning disc like a record needle is the head which is responsible for
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reading or writing data on the platter
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and then on the other side is a voice coil this this coil of wire is
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surrounded by a permanent magnet that yada yada okay giving you everything
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that you need to get your Loren force on
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so to move the ARM current flows through the coil creating a force that causes it
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to Pivot then just before the ARM of the
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hard drive reaches its desired location the current's Reversed bringing it to a
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stop exactly exactly where it needs to
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be in fact thanks to this Lightning Fast
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deceleration the arms of hard drives are able to be positioned within a millionth
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of an inch or one for thousandth of a
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human hair wow I got like five so now
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you might be thinking why not just use voice coils for everything that needs to
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move why don't we replace the Pistons in a car or use one to throw a ball for the
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dog well here come the
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downsides excessive magnetic for force and excessive heat are kind of problems
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if you make a magnet too large it can be
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difficult to tame the magnetic field it generates I mean a massive voice coil
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wouldn't be that great if it ripped all the fillings out of your teeth or more
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realistically like not in a cartoon wiped the data off of everything in a
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10t radius also anything that has a
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bunch of current going through a wire will tend to be a bit uh
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toasty if you've ever had your speakers emit the magic black smoke that's most
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likely why but this also doesn't mean that the applications of voice coils are
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limited to our two examples from before
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one of my favorite uses for them that you'll hopefully see more of in coming
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years are voice coil actuated camera
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stabilizers these are similar to gimal
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image stabilizers but instead of using several rotating Motors they use you
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guessed it voice coils to position the camera you got it again extreme speed
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and accuracy this thing huh wow uses
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badass voice coils and is so fast and so
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precise that it can create two 30fps
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videos from a single 60fps camera
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repositioning the camera between each frame to give the illusion that there
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are actually two separate cameras pretty
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cool so to say that I'm amped to see where we're headed as they continue to
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develop voice coil technology would be an understatement though I can't say
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that I have my hopes up about a new speaker that will make Nickelback sound
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head to freshbooks.com tequ and enter Techquickie in the how did you hear
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