Using a speaker to move objects

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Hey all,

I'm working on a project that requires me to move an object really fast. I'm hoping to use a speaker for this but don't know if any speakers can handle it. I know speakers can hit 1kHz and that some can move -+1/4" but are there any that can move that much at that frequency?

I'm going to be using a 1kHz sine wave for 30-45 second intervals trying to move a mirror (glued to the speaker cone?). The mirror is extremely light so I don't think it would affect the motion.

If anyone has seen/heard of speakers doing this I'd love to hear about it. If I were to try this would you recommend I use subs or midrange speakers? For me this is all about the motion and not about the sound quality so that might open up some more possibilities.

Finally, if this seems like blasphemy to some of you speaker connoisseurs I apoligize in advance, but you've got to admit it would be cool if it works...

Thanks
cScott
 
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Interesting question.

My instincts say no, and that you will not get that amount of deflection at 1Khz (and if you did imagine the volume level produced). The mass of a large cone and the suspension assembly would limit the deflection. As frequency goes up, speaker cone size comes down and the deflection is correspondingly less too.

I think you would have to try it is the only real answer and be prepared to wreck a few speakers. -/+ 1/4 inch is a lot at 1k. You might get a few millimeters with some serious voltage applied and the speaker in free air (not loaded in a cabinet).
 
Thanks guys

So I'm definately going to remove the cone and leave it in free air. I might also try to cut away some of the suspension too.

Right now I'm considering this speaker for the experiment: BOSS AUDIO P126DVC 12" 2300W Car Power Subwoofer DVC | eBay

It can take 2300W and is only $60. I'm concerned because it says xmax is 8mm but doesn't say if thats from rest or peak-to-peak.

I'm leaning towards car speakers because they seem cheaper and more durable but...I really don't know much so advice is appreciated. Right now I'm focusing on power and xmax, are there other specs I should worry about?
 
Go ahead and try it.

The mirror will move as soon as any force is applied, the issue is how far do you need to move it.

Keep in mind, a mass dominated system (as this is) will have 4X the excursion each time you lower the frequency an octave.

If your making a laser beam modulator, pivot the mirror, don’t move the whole thing.
Best,
Tom
 
You have not really described the application. I started working on a motion feedback system for a driver using a small polished section of the dustcap, bounced a laser off it to a CCD array. Kind of worked, but at that time I could not do the processing fast enough.

You say a light mirror. Half a gram? You only need to move one axis? Speakers have some nasty habits of not moving exactly in and out.

Why can't you use a TI piezo mirror array out of a DLP rear projection TV? That is what it was invented for.
 
keeping the voice coil centered, constrained to move axially without tipping, rubbing, requires both "suspension" and "spider"

you can use speaker parts as the core of a voice coil motor, without the cone - if you make a new suspension/axial bearing system

cutting away most of the area of the cone, just leaving spokes to the suspension may work - but may mechanically distort the cone too much - most of the stiffness comes from the full conical shape

"galvo-mirrors" often used in laser light shows are generally rotary actuators
 
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