BTH 'Rica Kellogg' loudspeaker, c 1929.
© Science Museum / Science & Society Picture Library
BTH 'Rica Kellogg' 12-inch energised moving-coil loudspeaker with integral rectifier unit. This was marketed as an 'American hornles' loudspeaker and was developed by Chester W Rice and Edward W Kellog at the research laboratory of the General Electric Company, for the Radio Corporation of America. It employs a moving coil suspended between the poles of a magnet and a paper cone diaphragm.