5H40.XX Drinking Cup Loudspeaker
A drinking cup, a small coil, and a magnet are turned into a loudspeaker.
A cup with a hole and a second coil are provided to allow demonstrating the construction of the speaker.
-  Waxed paper cup
-  Small coil
-  NdBFe magnet mounted on a rod
-  Radio
-  Banana plugs
-  3.5 mm plug adapter
-  Camera
- Please handle the 'speaker' with care. The coil is easily destroyed.
- The magnet is very strong and can cause injury (by pinching, shattering, etc.) if not handled with great care.
- The speaker action depends on the radial component of the field from the magnet. In a conventional speaker the magnet would sit in a permeable cup.
- In large lecture halls, use a camera to show the details of the construction.
- Turn on the radio and tune in to a radio station.
- Connect the banana plugs to the 3.5 mm adapter and the 3.5 mm adapter to the headphone jack of the radio.
- Move the magnet into the coil.
- Move the magnet in and out of the coil, noting the variation in sound intensity as the position varies.
- PIRA 5H40.XX
- From the article "Drinking-Cup Loudspeaker - A Surprise Demo" by Peter Heller, TPT 35, 334 (1997).
- Compare DaR W-425 Bite-a-Phone
- Don't attempt this at home!
- The coil consists of approximately 50 turns of #32 wire, wound on masking tape. One AA battery was used as the form. The hollow coil is epoxied into a hole in the base of the cup. Banana plugs allow connecting the coil to the headphone jack of the radio/cassette player. The Nd-B-Fe magnet is on a steel rod for ease of handling.
If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.