Looking for a good demo: make a speaker

[rink_er]

Hi,

My first post here...I have some physics background, but it was a while ago. I remember seeing an excellent demo on electromagnetics, using a magnet, coil, CD player, and the top of a cardboard box to make a speaker. I'd love to find a step-by-step so I can show this to a class of high schoolers. Any good ideas on where I should look?

I'd prefer not to trash the CD player if possible, and I need to figure out what kind of magnet to use, etc. Thanks in advance for any help!

 

[pantaz]

Have you checked instructables.com?

 

[rink_er]

Thanks--I found a couple of demos there! Plus, where to get the magnet--I was worried the magnet would be expensive.

However, I don't see any mention of impedance matching...has anyone tried this? is it an issue?

 

[Integral]

In the class I help with we use the output of an old boom box. The coil is about 2cm in diameter from about 3m magnet wire. For the magnet the teacher gets small rare Earth magnets (about $.50 each) the kids use every thing from Al pie plates to trash cans as the "speaker" simply tape the coil to the speaker and hold the magnet inside the coil. It is amazing how well they work.