Careers in Television and Video Production: Audio and Microphones

Common Microphones

When first entering a career in television or even film production, you will be working with a variety of similar microphones and audio-related equipment. If you work in an audio recording studio, the equipment becomes even more numerous. In this installment we will just examine common microphones (mics) you will most likely come into contact with. We shall begin with defining microphone impedance. Impedance simply means a restriction of the signal. Think of a garden hose with the water turned on. Placing your foot on the hose will restrict the flow, and by applying more pressure, you can even stop the flow of water. This is what impedance basically means.

In terms of mics and audio equipment, they are either low impedance or high impedance. Any audio device using mini-pins, or unshielded RCA cables is considered high impedance.1/4" 'phono' connections are rarely used in TV or film anymore, but they are also high impedance. As the name indicates, with high restriction the audio cable is only good for the length it is made. By adding extensions to a high impedance cable, you further restrict the signal, like applying more foot pressure to the garden hose. Add enough extensions to the mix and you will completely lose audio signal. Low impedance is more desirable in television and film, characteristic by their XLR, or 'canon' connections. For one, low impedance carries a clean, and noise-free audio signal. Second, having minimal (low) restriction, you can attach extensions to the shielded cables and lengthen them without signal loss. This comes in real handy when out on location. Low impedance mics only work with low impedance audio equipment. It is possible to take a low-impedance audio output from a playback device and rewire it for high impedance output (RCA), but you cannot take a high-impedance audio device (CD player, etc.) and rewire for low impedance playback device without conversion. Nor can a low impedance mic be used with high impedance equipment without some type of transformer to convert the signal.