Physics & Physical Science Demos, Labs, & Projects for High School Teachers

Build a Speaker from a Styrofoam Plate

Posted on: June 2, 2008


I found this on MAKE magazine’s site. If you don’t subscribe to this magazine, you need to check it out. I get so much stuff from it, I consider it a professional journal. The electronic edition gives you all the back issues, and every issue is packed with really cool things to build.

The speaker is so simple, and again, the students loved it. You use magnet wire, this time around 34 gauge, a couple of rare earth magnets, a styrofoam plate, some paper and glue. The magnets get glued to a wood or cardboard base. You make a coil of the wire that loosely fits over the magnets and glue it to the back of the plate (I used hot glue). The plate is held off the cardboard with a couple pieces of paper acting as a shock mount. You pass an audio signal through the coil. It generates a magnetic field and is attracted and repelled by the magnets, just like in a commercial speaker.

You can find the same design on this page, it might just be the same guy, I didn’t check.

When I made this the first time, I used 24 gauge wire. I would definitely go for something thinner, like 34 gauge. The wire is available from Radio Shack if you didn’t order it from your supply catalog. I believe the thinner wire will create a better sound.

I sacrificed an pair of dollar store headphones so that I could connect the speaker and I used an old transistor radio because I didn’t want to take a chance and damage a student’s iPod. Better safe than sorry.

Make sure to have the students put their hand on the working speaker. They can feel the vibrations that are creating the sound waves. After all, that was the point of the activity in the first place.

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2 Responses to "Build a Speaker from a Styrofoam Plate"

Regarding “You can find the same design on this page, it might just be the same guy, I didn’t check.”; Yes. I created the Styrofoam Plate Speaker and it was published by MAKE magazine.

You can really make a speaker (where you have to hold the magnet) out of anything – tape the coil of wire to a cup, or a blown up balloon (they make great speakers). Then attach the wire to your sound source, (old boom boxes are great), then bring the strong magnets near the coil of wire. One mistake I’ve seen people do: switching the direction of the wire in the loop – don’t fold the loop, coil it. By folding it half the current opposes the motion of the other half. Check out http://www.howtosmile.org/record/531

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