Some Facts on Microphones!!!

Tips for Independent Artist!!! The condenser microphone was by E. C. Wente, however it can also be called a capacitor microphone or electrostatic microphone—capacitorscondensers. The diaphragm of the mic acts like one plate of a capacitor, and the vibrations produce changes in the distance between the plates. There are two types depending on the way you get the audio signal from the transducer. DC based microphones, and radio frequency or high frequency condenser microphones. With a DC microphones plates have a fixed charge. The voltage across the capacitor plates changes with the vibrations in the air. The assembly of fixed and movable plates is called an "element" or "capsule". A constant charge is keep on the capacitor. As the capacitance changes, the charge across the capacitor does change very slightly. Within the time frame of the capacitance change the charge is constant and the voltage across the capacitor changes fast to reflect the change in capacitance. The voltage across the capacitor varies above and below the voltage. The voltage difference between the bias and the capacitor is seen across the series resistor. The voltage across the resistor is amplified for performance or recording. In most cases, the electronics in the microphone itself contribute no voltage gain as the voltage differential is quite significant, up to several volts for high sound levels. Since this is a very high impedance circuit, current gain only is usually needed, with the voltage remaining constant. AKG C451B small-diaphragm condenser microphone RF condenser microphones use a comparatively low RF voltage, generated by a low-noise oscillator. The signal from the oscillator may either be amplitude modulated by the capacitance changes produced by the sound waves moving the capsule diaphragm, or the capsule may be part of a resonant circuit that modulates the frequency of the oscillator signal. Demodulation yields a low-noise audio frequency signal with a very low source impedance. The absence of a high bias voltage permits the use of a diaphragm with looser tension, which may be used to achieve wider frequency response due to higher compliance. The RF biasing process results in a lower electrical impedance capsule, a useful by-product of which is that RF condenser microphones can be operated in damp weather conditions that could create problems in DC-biased microphones with contaminated insulating surfaces. The Sennheiser "MKH" series of microphones use the RF biasing technique. Condenser microphones span the range from telephone transmitters through inexpensive karaoke microphones to high-fidelity recording microphones. They generally produce a high-quality audio signal and are now the popular choice in laboratory and recording studio applications. The inherent suitability of this technology is due to the very small mass that must be moved by the incident sound wave, unlike other microphone types that require the sound wave to do more work. They require a power source, provided either via microphone inputs on equipment as phantom power or from a small battery. Power is necessary for establishing the capacitor plate voltage, and is also needed to power the microphone electronics. Condenser microphones are also available with two diaphragms that can be electrically connected to provide a range of polar patterns (see below), such as cardioid, omnidirectional, and figure-eight. It is also possible to vary the pattern continuously with some microphones.