Microphone Transducers

In the world of the professional audio engineer, no tool is more ubiquitous than the microphone. Skill with microphone selection and placement separates the inexpert recording engineers from the true professionals. Skill with microphones is based entirely on knowledge of the tool. One of the most basic skills is determining the proper transducer type for the proper application. Microphone transducers fall under three types; dynamic, condenser and ribbon.

Dynamic microphones are some of the most common microphones found in the recording studio, and elsewhere. Dynamic microphones are inexpensive to produce and relatively robust in construction. Dynamic microphones lack the brightness of condenser microphones due to a lack of responsiveness in the diaphragm of the dynamic microphone. The diaphragm is dampened do to being attached to the voice coil. Dynamic microphones typically have a cardioid polar pattern.

Condenser microphones are some of the most intricate and consequently most expensive microphones produced. Condenser microphones have some of the best quality frequency responses of any microphones, with a characteristic brightness in the high frequency range. This brightness is achieved by the thin metallic diaphragm, sometimes only 10 microns thick. Condenser microphones are also distinguished by their need for what is referred to as “phantom power.” Phantom power is 48 volts of electricity used to polarize the transducer or “capsule.” Sound is transduced into electric audio signal by the changes in voltage produced by the diaphragm changing distance in relation to the back-plate. Condenser microphones can have a variety of polar patterns, such as omnidirectional, bidirectional, cardioid, hyper cardioid and some condenser microphones can switch between two or all of these polar patterns.

Ribbon microphones are the oldest transducer design of the three. Ribbon microphones utilize a thin foil ribbon that oscillates between the poles of a large magnet. Ribbon microphones are considered fairly fragile due to the thinness of the ribbon and the necessity to be placed at a neutral point within the magnetic field. The ribbons can be easily deformed by high sound pressure levels. Ribbon microphones, by virtue of their design, have a bidirectional polar pattern.

Knowledge of transducer types eases the selection process when choosing microphones for specific applications. Transducer type is typically the first criteria considered when selecting microphones. Knowledge of transducer types helps in retaining knowledge of other criteria such as frequency response characteristics and polar patterns. It is therefore critical for any aspiring audio engineer to familiarize themselves with microphone transducers.

References

·      http://www.shure.co.uk/support_download/educational_content/microphones-basics/microphone_transducer_types

http://www.dawsons.co.uk/blog/what-is-phantom-power