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Does the voltage applied to a driver correlate to position, velocity or acceleration?
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Originally posted by speakerguy
Yes ...
Paul -
Applying voltage to a driver causes current to flow through the voice coil. This current induces a magnetic field which interacts with the drivers magnet to cause the driver to move. If the voltage is constant (DC), then the driver will move to an equilibrium position defined by physical parameters of the voice coil, spider, magnet, cone, and surround - and stay in that position. If the voltage varies with time, then the driver will continue to move. In order to produce sound, the cone has to compress the air in front of it, so the driver has to accelerate - which means that the voltage has to vary with time in a non-linear fashion.
That's at least a start....Keep an open mind, but don't let your brain fall out...
https://sites.google.com/view/sehlin...solutions/homeComment
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The way I understand it is like this-
The voice coil ideally exists in a uniform magnetic field, and when the current flowing through the coil changes there is a reaction force directly proportional to the change in current. Restated, the force on the cone due to the voice coil is proportional to the first derivative of the current passing through the coil.
Since the current passing through the coil follows Ohm's Law, there is a relationship between the voltage across the coil and the force exerted. Unfortunately, the impedance of the coil is not constant with frequency.
Most speakers are built with a voltage-source amplifier in mind. At resonance, the impedance of the speaker is higher. Your amplifier drives less current, but since the driver is at resonance it requires less force to maintain an even response.
Some interesting reading on current-source amplifiers is available here:
-Joe CarrowComment
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So can anyone give me an equation that relates voltage input to cone position?Comment
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Nevermind. Position, voltage, linear. Dur.Comment
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Think about this- if you feed a woofer 1volt p-p at 40 hz, you will see much greater excursion than if you give it 1volt p-p at 800 hz. Cone position is not linearly related to voltage. Force on the cone (acceleration) is related linearly to current. Position is the second derivitve of acceleration with respect to time.
Are you trying to get something specific from your question? Hopefully this stuff is interesting, but if you have something you're angling towards then we can directly to that.-Joe CarrowComment
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I'm trying to figure out servo subwoofers, and had to figure out what was the proportional and derivative signals were for a PD controller (position proportional, velocity derivative I believe now). So I should be able to take the output of an accelerometer, hit it with an intergrator to get the D signal, and another one to get the P signal. Now I think I need to weight the signal in some way to account for the fact that V1 at freq1 has a different excursion than V1 at freq2, but it should work (again, I think).
Of course I could be totally wrong, but I like trying to think this stuff out.Comment
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