Loudspeaker and Headphone Handbook, 3rd Edition

 

2	Transducer drive mechanisms
	John Watkinson

2.1 A short history

This is not a history book, and this brief section serves only to create a context. Transducer history basically began with Alexander Graham Bell's patent of 1876¹. Bell had been involved in trying to teach the deaf to speak and wanted a way of displaying speech graphically to help with that. He needed a transducer for the purpose and ended up inventing the telephone.

The traditional telephone receiver is shown in Fig. 2.1(a). The input signal is applied to a solenoid to produce a magnetic field which is an analog of the audio waveform. The field attracts a thin soft iron diaphragm. Ordinarily the attractive force would be a rectified version of the input as in Fig. ...