» MAKE: NOISE — Discuss this article

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• Low volume
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  My son and I made one over the break. We got it to work, but the volume is very very low. At full volume, you have to have your ear next to it to hear. Any clues as to how to increase the volume?
  
  More turns? I am using 70 turns of the red magnet wire from Radio Shack.
  
  Stronger magnets? I am using a stack of about one inch dia magnets from RS.
  
  And how does one measure impedance as suggested in the article?

  Posted by fll-freak on January 02, 2008 at 18:24:36 Pacific Time

• It really works!
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  Not that I doubted it, but I had to try for myself.
  
  It went together quickly. I got the enameled wire from a junk box miniature audio transformer.
  
  Hot glue works great, except the magnet is a great heat sink, so you have to work fast before it hardens.
  
  I found the easiest way to hold the voice coil centered while gluing was to put a metal something or other (a hinge for me) behind the plate for the magnet to stick to while I centered it.
  
  The plate sat too low on the business cards so I doubled them up, but I think I'm losing efficiency that way. I suspect using 3 cards 120 degrees apart would work better and keep the plate from leaning as it tends to do.
  
  Thanks for the fun project. (goes to nurse pinched fingers after playing with magnets)

  Posted by getaya on November 18, 2007 at 16:55:27 Pacific Time