#1 Operating Principle
- How sound is converted to an electrical signal.
Dynamic Mics (dynamic transducer), good for loud sounds but not good for distant or quiet sounds. Good for vocals and horns but not string instruments.
Condenser Mics (condenser transducer), better high frequency range, good for piano, string instruments, quiet and distant recording, and percussion. Mics can be much smaller.
#2 Frequency Response
- Range of sound a mic can reproduce.
- How sensitive the mic is within that range.
Flat response (wave pattern) is equally sensitive to all frequencies so it reproduces voice as well as instruments with little variation and is good for acoustic instruments and vocal groups and orchestras
Shaped response (wave pattern) adds clarity to response to vocals and guitars with an increased sensitivity to high frequencies. Mics with a decreased sensitivity to low frequencies work better at not picking up room noise and vibration and counter-acts the buildup of bass that comes from the mic used too close to the source, called proximity affect.
#3 Polar Patterns
The polar pattern is how the mic responds to sounds coming from different directions. The polar pattern tells you how the microphone should be placed to maximize the response and minimizing the feedback and background noises.
Omni directional polar pattern is a sphere so it can pick up everyone sitting at a table but cannot be aimed to pick up one source better than another.
Uni directional mics picks up less ambient noise and less feedback. The cardioid pattern is most common and is a little more than half of the sphere as its pickup pattern. More sensitive to sources in front of the mic and not as much behind the mic.
Bi directional mics are equally sensitive in front of and behind the mic. It is good for a two person interview or to isolate one source in a group as long as there is nothing behind the mic.
#4 Electrical Output
The mic needs to be compatible with the mixer, recorder or computer, otherwise you may get humming, buzzing or no audio at all.
Usually measured in decibels or dbs. minus 50/-50 dbs. is a baseline. -30 = more sensitive, -70 dbs. = less sensitive.
Impedance = compatibility with other devices and long cables.
Low impedance mics of < 600 ohms, can be used with up to 1000 feet of cable with no sound loss.
High impedance should not be used with cables more than 20 feet.
Balanced mics reject noise will with long cables connected to balanced input on your mixer.
Unbalanced mics are more noisy but good with short cables.
XLR cables are good with balanced mics.
Self-noise levels are good for picking up quiet conversation. 30 dbs. = more hiss, 10 dbs. = less hiss.
Maximum SPL is the loudest sound a condenser mic can handle without distortion. Important when mic-ing an amp or a drum.
Dynamic range is between the maximum SPL and the self-noise. Usually need phantom power for your mixer if the mic is not battery powered.