Making a Speaker

by Regan Lum

Introduction:
A speaker is a device that converts an electronic signal into sound. The speaker you will build (see figure 1) consists of a Styrofoam or paper cup, a coil of wire, a permanent magnet, and a signal source. The electronic signal goes through the coil and creates a varying electromagnet. The attraction and repulsion between the electromagnet and the permanent magnet cause the cup to vibrate and produce sound.

figure 1
http://cse.ssl.berkeley.edu/img/cupspker.gif (http://cse.ssl.berkeley.edu/img/cupspker.gif)
Purpose:

In this laboratory, you will explore how a speaker works.

Materials:

1 permanent magnet
2 feet of wire
1 pencil
tape or glue
1 Styrofoam or paper cup
1 signal source (tape player)
1 plug with alligator clips for tape player
Procedure:

Assemble material as shown in figure 1.

Leaving about 10 centimeters on the end, wrap the wire around a pencil to make a wire coil and tape or glue it to the bottom of the cup. The coil should be about 1 centimeter in diameter and contain about 15 coils.
Strip the insulation off the ends of the wire.
Place the magnet on the wire coil.
Connect the signal source (tape player).
Adjust the apparatus until you get sound coming out of your speaker.
Conclusion

Does the volume control on the tape player work on your speaker?
What kind of sound quality do you get out of your speaker? Compare the loudness and the clarity.
How does the sound quality compare with your string walkie talkie?
Explain how your speaker reproduce sound.