Rochelle-salt crystals have the property of becoming physically distorted when a voltage is applied across two of their surfaces. This property is the basis of the crystal type of speaker driver, illustrated in Fig. 4.2.
Fig. 4.2 Schematic representation for a crystal type speaker
The crystal is clamped between two electrodes across which the audio frequency output voltage is applied. The crystal is also mechanically connected to a diaphragm. The deformations of the crystal caused by the audio frequency signal across the electrodes cause the diaphragm to vibrate and thus to produce sound output.
Crystal speakers have ...