I designed this speaker as an easy, inexpensive way for artists to embed sound in their work. I also created it as part of a larger (somewhat quixotic) quest to knit working electronics. The speaker can be made with or without knitting. Instructions for both designs are included.
The Basic Design
Rows of parallel magnet wire, glued between two pieces of paper, carry the audio signal. The wires are positioned over the mid-section of the magnet.
This creates an effective speaker because hard drive magnets are dipolar.
The broad face of the magnet has both a north and south pole.
When the red line on the paper rests on the red line on the magnet, it produces a clearly audible speaker.
Find a jig to wrap your wire around.
Tape one end of the wire down on the jig. Wrap the wire tightly around the jig to create at least 10 parallel rows of wire. Avoid twisting. Once you're done wrapping, tape the other end of the wire down as well.
In the photos, I'm wrapping the wire on a warping board, but a large square of cardboard will work just as well. Place a piece of double sided tape along opposite edges of the cardboard to hold the wire in place as you go.
The total width of the wires should be narrower than the length of your hard drive magnet.