Specifications

The output wiring scheme of a microphone can be
either balanced or unbalanced. A balanced output carries
the signal on two conductors. A shield surrounds these the
two conductors to keep out unwanted signals. The signals
on each conductor are the same level but they are of
opposite polarity. A balanced (or differential) input is
sensitive only to the difference between the two signals and
ignores any part of the signal which is the same in each
conductor. Because of the close proximity of the two
conductors in a balanced cable, any noise or hum picked
up by the cable will be of the same level and the same
polarity in each conductor. This common-mode noise will
be rejected by the balanced input, while the original
microphone signal is unaffected. This greatly reduces
potential noise in balanced microphones and cables
An unbalanced output signal is carried on a single
conductor (plus a shield). An unbalanced input is sensitive
to any signal on that conductor. Noise or hum which is
picked up by the cable will be added to the original
microphone signal and will be amplified along with it
by the unbalanced input. For this reason, unbalanced
microphones and cables are never recommended for long
cable runs, or in areas of high electrical noise.
The two most common microphone output configura-
tions (and mixer input configurations) are balanced low
impedance and unbalanced high impedance. Since all
high-quality and even most medium-quality microphones
have balanced, low impedance outputs, this is the
recommended configuration for the majority of meeting
facility sound system applications.
5) Physical design: How does the mechanical and
operational design relate to the intended application?
Microphones for meeting facility sound applications
include several typical designs: handheld; user-worn; free-
standing mounted; and boundary or surface mounted.
Each is characterized by a particular size, shape, or
mounting method that lends itself to a specific manner of
use. In addition, some microphones may be equipped with
special features, such as on-off switches, that may be
desirable for certain situations.
Handheld types are widely used for speech in many
areas of meeting facility sound. Since they are usually
handled, passed from person to person, or used while
moving about, they must have a very effective internal
shock mount to prevent pickup of handling noise.
In addition, they are often used very close to the mouth
and should therefore be equipped with an effective “pop”
filter or windscreen. Size, weight, and feel are important
considerations for a handheld microphone.
User-worn microphones include clip-on types that
may be attached directly to clothing, lavalier styles worn on
a lanyard around the neck, or possibly head-worn types.
These are used when a relatively unobtrusive microphone
must be located close to the user and especially for
applications in which the wearer moves about or needs
hands-free operation. Size and appearance are critical in
the selection of user-worn microphones.
14
MEETING FACILITIES
Audio Systems Guide for
Connectors and cables
A selection of mic designs