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Speakers and lasers..

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SenKat

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Okay - I TRIED doing the little thingie with two speakers, some FS mirrors and a laser - failed miserably - I guess there was not enough bass output by the speakers....assuiming I am going to tear these suckers apart (you can bet on it !) What type of speakers should I pick up at the local radio shack or whatever ? You can assume correctly that I am 99% accustically inept - I USED to know car stereos a loooooong time ago...forgotte most of it though...can anyone help ?
 

Beefygt

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Hey, I used to be into car audio too! :p

To do this right, you need a speaker with a "spider" (this is what keeps the dust cap in place (it is kind of a two way spring if you will)). I don't think many small home speakers have them (I could be wrong)... As long as it is a speaker with a spider, and you have enough power going to the speaker it should work. It is also mainly the bass that will really push the mirror. It is recommended that the cone is removed, and to just mount the mirror on the dust cap. This will eliminate distortion you might get from the mirror weighing down the speaker. This is optional though...

To understand more how speakers work (if you really want to know :p):
http://electronics.howstuffworks.com/speaker.htm

Anyway, when I did the audio in my car, I got most of the electronics from this site:
www.etronics.com

Most speakers form there should work. The only thing is that even for a cheap site, they might cost a lot of money. :-/

As for Radio Shack (I LOVE THAT STORE!) just about anything should work from there. Sub woofers will work the best!

One more thing... Speakers have something called Xmax (The measure of a speaker cone's maximum excursion in one direction while maintaining a linear behavior). The higher the Xmax for this project, the better! ;)

Hope this helps! ;D

P.S. Links on how to do this:
http://hackedgadgets.com/2006/04/01/speaker-laser-light-show/
http://www.wikihow.com/Make-Your-Own-Laser-Light-Show
http://www.dangerouslaboratories.org/laser1.html
http://www.laserfx.com/Science/Science8.html
 

Ragnarok

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I built my first set of X-Y scanners from some Pioneer sixes a loooong time ago in high school days. I cut out the cones and cut the frames down so that all I had left was the magnet, voice coil and spider, and enough frame to use as a support for a strut that went across the speaker about a half of an inch above the voice coil. I used some of those nylon hinges - the ones they use on RC planes - to make an arrangement where one end of the hinge was epoxied to the voice coil, and the other end to the rigid bar across the frame, so that when the voice coil moved back and forth it would push the hinge to and fro, on top of which which was mounted a small first surface mirror. They worked pretty good for being a "rig". Here's an attempt at an ASCII diagram (note - the speaker magnet is not shown)


hinges with mirror
strut --> ________o-===-o
\ | /
frame--> \ | /
\ | /
spider/dustcap--> \^^^^-----------^^^^/
voice coil --> | |
 
S

SenKat

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DANG ! It musta taken you a while to do that diagram !!! Thanks for all the hints, guys ! The only part where I ma lost now is the "spiders"....and I ma supposed to CUT away the cone itself ? I will hopefully be stopping at the Radio Shack on my out and about today - so hopefully I can find some woofer type gooooood bass response speakers there !
 
T

timelord

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Use a big sub-woofer and attach your mirrors to it. ;) I guarantee you'll get the desired effect...
 

Ragnarok

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SenKat said:
The only part where I am lost now is the "spiders"....and I am supposed to CUT away the cone itself?
You don't have to cut the cone out if you don't want or need to, but if you do, leave the dust cap in the middle to attach the hinge to.

A speaker is just a push-pull voice coil motor, and since I didn't need the sound reproducing ability of the cone, I cut that out of it and removed most of the frame so as to reduce the size of the unit; that way I could get two of them close enough together to do X-Y scanning.

The "spider" is usually seen as a corrugated circular stiff yellow cloth piece behind the cone. It is attached to and is the suspension for the voice coil. Don't cut that!

In my experience, simply gluing a mirror to a speaker provides inferior results, because the major motion of the speaker cone/mirror combination is linear (back and forth). No matter what the "throw" of the speaker, it's only the residual components (standing waves, flexing, suspension non-linearities, etc.) that contribute rotational motion to the mirror.

By using a pair of hinges the major linear motion of the voice coil is converted into a rotational motion, and with the short distance between the hinge points you don't need lots of power to move the beam across a wide angle.

A 4"-6" speaker will provide plenty of throw if you use hinges.
 
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Proctor

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low hz on subwoofer wont be enough, you need very fast movements. Also, don't glue the mirror to the speaker, tape it.
 

FokoF

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Limpit or Limpid, not sure about the spelling, subwoofers are the best. they are about 4inches and kick out the lower frequences. Most subs will play at around the 100Herts range( 100 movments per second) so they should give the look you want.
Good luck
 




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