Sound Recordist Notes - Microphone Types
Microphones
A microphone is a transducer that converts acoustical sound energy into electrical sound energy.
The three most common types are;
* Dynamic (or moving coil) microphone.
* Ribbon microphone.
* Condenser (or capacitor) microphone.
The Dynamic (Moving Coil) Microphone
* Robust.
* Widely used in the sound reinforcement industry (particularly suitable for hand-held use).
* Usually fitted with wind shields (bulbous, foam filled wire mesh which attenuates wind noise and ‘p-blasting’ from the vocalist’s mouth).
* Often provided with built-in bass attenuation to compensate for the ‘proximity effect’ (or bass tip-up, an effect of directional microphones when sound sources have their bass frequencies boosted when they are close to the microphone).
* The design produces a ‘peak’ in the upper-mid frequency range (around 5 kHz) and a rapid fall-off in response above 8 or 10 kHz; this means the sound quality is restricted compared to other mic types.
Dynamic Capsule
Used for;
* Vocals; the boosted upper-mid frequencies help to improve intelligibility.
* Drums; dynamic mics can withstand high sound pressure levels (SPL’s), which might damage other mic types.
* Guitar Amplifiers; amps can also benefit from the ‘presence’ lift caused by the upper-mid frequency boost.
Typical dynamic designs include Shure’s SM57 and SM58.
The Ribbon Microphone
* At best, is capable of very high-quality results.
* Can record frequencies between around 40 Hz to around 14 kHz.
* Smooth frequency response (frequencies are recorded without the microphone boosting or cutting them).
* Delicate; can be physically quite large; the larger the ribbon, the larger the area to pick up sound waves and, therefore, the greater the electrical output .
Used for - Acoustic instruments, classical ensembles.
The Condenser (Capacitor) Microphone
* The diaphragm can be very thin and light (a few microns thick) and so has less inertia. This means that the diaphragm can respond to higher frequencies more effectively than the dynamic microphone.
* The typical frequency range is around 12 Hz to 20 kHz, but can exceed the range of human hearing at both the high and low ends of the spectrum.
* Due to the microphone’s preamplifier, condenser mics offer the best noise performance and the highest sensitivity of any studio microphone.
* Can be made with virtually any response pattern.
* Robust enough to handle many studio and live applications.
* Needs powering, either by a battery or phantom powering via a desk.
* Cannot handle high SPL’s, unlike the dynamic type.
Used for;
* Any instrument where high frequency response is required (for example, cymbals or acoustic instruments).
* Vocals.
Designs such as the small diaphragm AKG C1000S and the large diaphragm Neumann U87 are typical condensers.
Mic & Line Levels
Mic level is -56 to -40 dbm. Mic outputs are normally quite low; around a millivolt (1 mV) and is the typical output directly from a microphone. You need a preamp to amplify a microphone to line level – eg a mixer.
Line Level
Nominal level of around 1 volt - around 60 dB higher than mic level. Commonly used as the output level of a mixer – remember this when setting camera audio input levels.
— Posted by Matt in Careers in Sound, Glossary, Technical | No Comments
