Crystal microphones are quite inexpensive and have both high output and high impedance. When a long cable is used, both the high output voltage and the high-frequency responses are altered. Crystal microphones have an output impedance of over 100,000 ohms and an output level that ranges between -48dB and -60dB. Some can produce small emf’s when under stress. This type is the most common in lower-cost systems.
The Workings of These Microphones
All crystal mics include a finger-shaped slice of crystal held on one end. They have an apex of a cone secured against the other side. When someone applies pressure waves, this cone pushes and bends the crystal. In this way, it can released. In this event, there is a production of voltage within the crystal slice. When a single slice of the crystal is replaced by two joined slices and pressure is applied, one slice gets compressed as the other one gets stretched. Hence, the result is the production of equal and opposite voltages.
The double crystal device is a biomorph. This type of transducer has many drawbacks. One of them is that the whole process limits both the frequency response and the transient response. Another disadvantage are the resulting resonances resonances due to both the crystal and the cone.
An Assortment: Various Kinds of Crystal Microphones
The creation of microphones is not the same in all cases. In this particular one, there are many different construction-types of crystal mics. For instance, a better quality crystal microphone functions when the cones are triggered through a cantilever. The name of many crystal elements merged is multimorph. This process involves a cone that moves when the pressure waves act directly on the crystal. While the output is lower, the frequency response is better. Therefore, the cone resonance is completely removed.
As a final note, it’s worth mentioning that the crystal within a crystal microphone works as an insulator and the device works as a capacitor. The typical crystal microphone is non-directional. Natural crystal mics are quite delicate and are highly affected by humidity and high temperatures.
