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Topic: How do speakers work? |
Richard Sinkler
From:
aka: Rusty Strings -- Missoula, Montana
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Posted 14 Jul 2000 4:45 pm |
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I know sound is the movement of air at certain frequency, but how does a single speaker handle all the different frequencies that make up a song? I assume the cone vibrates at a certain freqency to move air, but how does it vibrate to make all the notes of a song at one time?
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Carter D10 8p/10k
Richard Sinkler BS, www.sinkler.com
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C Dixon
From:
Duluth, GA USA
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Posted 14 Jul 2000 6:31 pm
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Just exactly like your eardrum works. No matter how many instruments. No matter what they are playing. No matter what the level is, at any given instant in time the cone just like the ear drum is moving either in or out.
How a speaker emulates so many seemingly different things at once, again is just like our ears. It is WHAT happened a micro second ago and what WHAT happens a micro second from now.
This is what sound is. It is the CHANGE in movement more than the movement itself. In fact if it did NOT change directions and very fast we probably would perceive nothing and a speaker would produce Nothing.
Take a full 120 pieces symphony orchestra all playing at one time. Many sounds coming out right? However at any given intant in time, it all melds down into one movement of air. EVEN though the composite appears to be full of so many things, remember that speaker cone is either moving out or in. Just like our ear drums.
BUT, it is the CHANGE from in to out or vice versa and how long that change is before another change that permits a speaker to move air in a given pattern and our ears to convert that movement of air pattern to a brain wave that we have been programmed since birth to recognize and we call it sound.
But in reality, it is just movement of air that is constantly changing direction according to a myriad of almost infinite patterns.
Clear as mud? Don't feel bad. I don't understand it either 
God bless you,
carl |
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Jim Cohen
From:
Philadelphia, PA
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Posted 14 Jul 2000 7:22 pm
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Y'know, Carl, that is really in-freaking-credible, don't you think? Just boggles my mind to think about it.
(Of course, he has a very tiny mind to boggle)
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Richard Sinkler
From:
aka: Rusty Strings -- Missoula, Montana
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Posted 14 Jul 2000 8:47 pm
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Thanks Carl.
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Carter D10 8p/10k
Richard Sinkler BS, www.sinkler.com
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Bill Llewellyn
From:
San Jose, CA
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Posted 15 Jul 2000 8:07 am
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It is an amazing thing. A single medium, which can have only one position at any point in time as it vibrates, can be simultaneously carrying dozens, even hundreds of individual sounds.
The idea is most easily understood if you consider two pure tones (called sine waves) which are fairly far apart in frequency. Try this: Let's say the palm of your hand represents a speaker cone's position. Put your hand out in front of you, thumb up. You can wave your arm from left to right, slowly back and forth in front of you, and you will roughly be reproducing a very low frequency sine wave (too low to hear, of course) at your palm. Now, keep your arm swinging slowly left to right, and start wobbling your wrist like your're trying to make a breeze with it. Your palm now is moving back and forth with both the slow oscillation and a faster oscillation, literally summed together into a single, compound "signal". A speaker cone carrying, say, a 100Hz tone and a 1000Hz tone would do exactly the same thing. (In engineering terms, that's called superposition, where you superimpose one function on top of another with no distortion involved.) You can add up an arbitrarily large number of tones this way, and all can be carried by a single mechanism vibrating as a sum of all components. Even though the resulting motion (waveform) may resemble a chaotic jumble, all the tones are there in their individual glory. Like I said, it's amazing.
More amazing than that: think of your TV cable. It is just a pair of wires. At any instant in time, the voltage on the wires can have only one value. It's changing really fast, but if you took a snapshot of it with an infinitely fast shutter, you'd see it frozen at just one voltage. You may be able to tune in hundreds of channels, but all of those are being carried by that one varying voltage. Then there's radio broadcast. From your AM band (500,000 Hz) to radar frequencies (10,000,000,000 Hz) there are thousands of signals - radio, TV, cellphones, civil authorities, aircraft, satelite - all squashed into a single "voltage" (electromagnetic signal, actually) which also can have only one position or value at any given instant in time. Astounding.
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Bill * MSA Classic U12 * email * my online music
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Smiley Roberts
From:
Hendersonville,Tn. 37075
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Posted 15 Jul 2000 1:37 pm
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I took-up (along w/ some space) some electronics in high school,& never got past 2 tin cans & a string! 
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~ ~
©¿© ars longa,
mm vita brevis
-=sr€=-
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C Dixon
From:
Duluth, GA USA
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Posted 15 Jul 2000 3:47 pm
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Smiley,
How true. I tried two tin cans and a string. It did not work too well but get this, my wife did something that blew my mind.
She had our grandkids over one day and she was out in our front yard with them. She had taken a string and attached it to two styrofoam coffee cups. The string was over 150 feet long!
She said it is working great as she excitingly ran in to tell her psuedo engineering hubby.
Of course I said, "yeah right!!"
My grandkids said, "papaw, we can hear each other!" Again I had something to say. You, know me
Imagine the unbelief and awe that engulfed me when I heard my little grandson quite well.
Never ever did two tin cans really work when I was younger. But leave it to my precious wife to come up with some genious idea that defies all my years of training!
God bless her forever!
carl |
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Bobby Lee
From:
Cloverdale, California, USA
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Posted 16 Jul 2000 8:48 pm
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| Uh-oh, now Carl's gonna invent a styrofoam-and-string steel guitar pickup. Don't tell Keith Hilton! |
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