I doesn't look like a high-tech speaker but it works well. I didn't expect a high quality of the sound from this made-from-scratch speaker but it performs very well, better than I expected.
A speaker is just a magnet, a coil, frame and a cone or any material that can make the air vibrate. Here is the bill of materials that I used to build this speaker:
Cut two long pieces of paper vertically, half inch wide. (0.5 inches by 11 inches).
Roll one strip of paper over the magnet. Use some tape to keep it but DO NOT put tape on the magnet. The Cylinder needs to be removed from the magnet, so do not tape the paper to the magnet.
Roll the second strip of paper over the first one. Do not glue or tape each one with the other. Roll it individually.
Use tape to keep the paper as cylinder.
Using the ballpoint pen, Draw three lines on each side of the business card. There is no exact measure but try to draw the lines at least half inch away from the corners (0.5 inches)
Fold the business card using the lines as reference. The lines will help to fold it.
Remove the magnet and glue the paper cylinders at the center of the business card. Using instant glue or hot glue works ok.
Once the glue is dry, put the magnet back inside the cylinder and start making the coil.
I do not recommend to use wire AWG 30 as it needs a lot of loops. Using AWG 32 or 34 will need about 40 to 50 loops. After you finish winding the wire, use some tape to secure it.
Do not try to make the coil without attaching it to the business card, it is an almost impossible task.
Make the frame approximately the size of the business card and not higher than one inch.
I used Lego bricks because I had some handy. Wood may work better. Try not to use any metal that can be attracted by the magnet.
Put some glue on the magnet when it is inside the cylinder. On this step, Hot glue works better than instant glue. Be sure the glue doesn't touch the paper cylinder.
Assemble the speaker and let the magnet to fall and glue itself to the frame. It will allow to have the magnet exactly on the center of the coil. Wait until the glue dry.
Once the glue that attach the magnet to the frame is dry, remove the business card and the coil. Try not to disturb any piece on the frame or the business card.
Now, remove the inner cylinder. Is ok to break it as it will discarded. Try not to damage the secondary roll [or paper cylinder].
The last step is to put back the coil to the frame. The coil should not touch the magnet and should move freely.
I did connect my home-made speaker to my laptop and here is how it sounds like:* WAV File, 1MB
6/17/2007 Update:
I did a modification to my homemade speaker and it improved the volume of the sound. A simple disposable [plastic] cup amplifies the sound mechanically. The sound is amplified because the resonance of the plastic cup.
Once the "Speaker" is assembled, cut a hole on the business card. (see next photo)
Glue the coil to the bottom of the cup instead of the business card.
Glue the plastic cup to the business card and that's it! Now it looks like a real speaker, a home-made speaker, just built from scratch.
Most of today speakers have a resistance of 8 Ohms. This homemade speaker may have less than 8 Ohms and may not be able to make loud sounds but basically it shows exactly how it works.
Using different materials, may cause the sound to change, even to make it louder.
