Field Coil

This is a field coil from an electrodynamic speaker, otherwise just known as a field coil speaker. Up until the 1950’s, field coil speakers were the norm in anything that played audio and was plugged into a wall. The field coil created the magnetic field that the speaker coil would work with to turn an electrical signal into audio. In the 1950’s, permanent magnet technology advanced to a point where field coil speakers became obsolete. Field coils like the one pictured contained hundreds of feet of enameled copper wire. They were a popular way for radio hobbyists to reclaim useable copper wire for winding antenna coils and such. They could also be left intact and used as choke coils in power supplies or for homemade electromagnets. We believe Ed used this in his electrical experiments. It was found in his shop exactly as seen here, devoid of the rest of the speaker but still has its electrical terminals.