Magnetostatics Analysis, Design, and Construction of a Loudspeaker

Making a loudspeaker is a very rewarding hands‐on activity that can be used to teach about electro‐magnetism and sound waves. Several loudspeaker designs have been described in this magazine.^1–4 The simplest loudspeaker⁴ has only a magnet, a coil, and three plastic cups. The simpler devices^3,4 require a powerful amplified output, e.g., from a boom box. The more complex devices^1,2 can operate using the smaller electric current from a CD player earphone output. Unfortunately, the procedure to make a more efficient loudspeaker is lengthy and less recommended to some high school students, involving a hot glue gun, a safety razor, five‐minute epoxy, etc. Our loudspeaker, a variation of Heller's,² is both simple in construction and efficient in operation. An analysis of the magnetic field distribution helped us in the design of this loudspeaker.