Before it can be used for anything serious the signal needs to be amplified, usually to line level (typically 0.5 -2V). They are very easy to use and generally have good to outstanding
frequency response. The only reason it is not used more extensively is
the cost of the special microphone and decoding circuit, well over
$1,000. The stereo effect comes from the fact
that the instruments on the right side are on-axis for the right
channel microphone and somewhat off-axis (and therefore reduced in
level) for the other one. A mic preamp is
very similar to a radio reciever, so the cable must be prevented from
becoming an antenna. (I often
laugh when I attend concerts and watch people using this setup fuss
endlessly with the precise placement of the mics. (If you buy one Neumann mic, you are paying for
five!). The second problem, and a severe one, is
that the actual shape of the pickup pattern varies with frequency. • A microphone, is an acoustic-to-electrical transducer or sensor that converts sound in air into an electrical signal. In a
concert recording, where the point is to document reality, and where
individual microphones would be awkward at best, it is most common to
use two mics, one for each speaker. Sustained overdriving or extremely
loud sounds can permanently distort the diaphragm, degrading
performance at ordinary sound levels. • With about $400 worth of
mics and a reliable tape deck, it is possible to learn to make
excellent recordings. Many engineers use pop filters to keep the artist at the proper
distance. This changes the capacitance, and thus, voltage across the plates vary proportionally as well. That is because the various
components of an instrument's sound often come from different parts
of the instrument body (the highest note of a piano is nearly five
feet from the lowest), and we are used to hearing an evenly blended
tone. Some microphones have tiny built-in amplifiers which boost the signal to a high mic level or line level. For low frequencies, this is an omnidirectional microphone. Bidirectional mics also exhibit this phenomenon. A magnet produces a magnetic field which surrounds the
coil, and motion of the coil within this field causes current to
flow. Microphones produce a very small amount of current, which makes
sense when you consider just how light the moving parts must be to
accurately follow sound waves. Stereo sound is an illusion of spaciousness produced by playing a
recording back through two speakers. Frequency response is just as good as an omni, at least for sounds
that are not too close to the microphone. A "shotgun" mic carries these
techniques to extremes by mounting the diaphragm in the middle of a
pipe. Condenser types require batteries or power
from the mixing console to operate, which is occasionally a hassle,
and dynamics require shielding from stray magnetic fields, which
makes them a bit heavy sometmes, but very fine microphones are
available of both styles. As the sound waves hit the diaphragm, it moves, changing the distance between it and the other plate. This is the way any diaphragm will
behave if sound can strike the front and back equally. Having
chosen one with appropriate sensitivity and pattern, (and the best
distortion, frequency response, and noise characteristics you can
afford), you simply mount it where the sounds are. It is posible to exaggerate the directionality of cardioid type
microphones, if you don't mind exaggerating some of the problems. The principles are the same as those that produce electricity
at the utility company, realized in a pocket-sized scale. To be useful for recording or other
electronic processes, the signal must be amplified by a factor of
over a thousand. The methods may be different based on the kind of mic. No matter how they are mounted, the microphone that points to the
left provides the left channel. Most plastics conduct electricity when they are hot
but are insulators when they cool.) Now the signals from the two microphones are not merely kept in
two channels and played back over individual speakers. The reality is
different. A so called stereo microphone is really two
microphones in the same case.