A Demonstration Speaker

This page is intended to support workshops given by Hila Science Camp.

Speakers are devices that use a varying electric current to control the magnet field of an electromagnetic coil to create sound.  Sound occurs when the varying field reacts with the field of a permanent magnet creating vibrations and sound waves.

Here is a circuit to use with your speaker:
555 Two-Tone Alarm

basic speaker


speaker cone circle

11 cm diameter circle with radius line drawn.
This creates the cone.

A cone

Create a cone from paper.
This cone is constructed from an 11 cm diameter circle cut on
a radius line and overlapped 3 cm.


Create a face plate to hold the magnet and secure the cone in place.
This face plate is 12 cm square.
The magnet is mounted with double-sided tape with cardboard as a spacer.

wind coil

Wind a coil around any convenient cylinder (3 to 5 cm).  A film canister works well.
This coil uses 1.5 meters of  28 gauge magnet wire.
Leave 15 cm of wire for each end.


Secure the finished coil by looping the ends through the coil.
Sand the enamel off of the ends of each wire.

cone and coil

Tape the cone to the face plate with magnet inside.
Center the coil over the top of the cone and tape in place.


Create a bracket from folded card and tape it to the face plate.


The finished speaker.

Caution:  This speaker may damage a radio or other electronic device.  This speaker has a very low impedance (similar to resistance) and could short circuit some electronic devices damaging them.

This speaker is very inefficient.  Sound levels will be low, you have to have your ear close to the face plate to hear anything.

Here is an electronic circuit you can build to test your speaker with:  -  555 Two-Tone Alarm