Specifications

Condenser microphones offer several benefits. The most important of

these is that they can be made very small, which is why all miniature lavalier

microphones are condenser types. Condensers tend to be very sensitive to

the extreme low and high frequencies, and usually have a very crisp, clean

sound. Their built-in preamplifiers allow condenser mics to provide higher

output than dynamic mics, meaning that for a given sound level, a stronger

electrical signal comes out. This may be helpful when you are trying to pick

up someone who speaks very softly, or who is further away.

You’ll encounter one inconvenience in using condenser mics, however, in

that the preamplifier requires electricity to work. On some microphones, this

can come from a battery carried inside the handle of the mic or in the

preamplifier pack. Power can also be supplied from the mixer or other

equipment that the mic is plugged into, if it is so equipped. This is called

phantom power, and will be discussed later.

ELECTRICAL IMPEDANCE

Impedance is an electrical characteristic of audio equipment, just like

voltage or current. It is expressed in ohms, the symbol for which is Ω.

Microphones are typically classified as being low-impedance

(also called

low-Z) or high-impedance

(also called high-Z). For professional

applications, only low-impedance microphones should be used. High-

impedance microphones usually begin to sound muffled due to a loss of

high frequencies when used with a cable longer than 20 feet. One of the

advantages of low-impedance microphones is that they allow you to use

very long runs of cable (over 1000 feet) with negligible loss of sound quality.

It’s usually not difficult to tell if the microphone you’re using is high-imped-

ance or low-impedance; just look at the nameplate or specification sheet.

The words “high-Z”, “high impedance”, or a rating of 10,000 ohms or higher

all indicate a high-impedance microphone. “Low-Z”, “low impedance”, or a

rating of 600 ohms or less indicate that the mic is low-impedance. High-

impedance microphones can only be connected to high-impedance audio

inputs. Use of a matching transformer

(which will be discussed later) can

facilitate connection of high-impedance mics to low-impedance inputs, or

low-impedance mics to high-impedance equipment.

It is important to note that the impedance of a microphone should not

match the impedance of the input to which it is connected. In fact, matching

the impedance causes a significant loss of signal level. The tradition of

matching impedances originates in the early days of electronics, when

amplifiers were based on vacuum tubes. With modern transistorized

electronics, low impedance devices (such as microphones) should always

be connected to an input whose impedance is higher — preferably 5 to 10

times higher. For this reason, the inputs on professional mixers typically

have an impedance of 1000 ohms or higher.