Speakers are usually classified as full range, tweeter, midrange,
woofer, or sub-woofer. A full range speaker is designed to handle
the full range of sounds most people can hear. A single amplifier
is all that is needed to power a full range speaker.
However, tweeter, midrange, woofer, and sub-woofer speakers are
only designed to handle a portion of the sound spectrum. These
speakers require a device called a Cross-over to work
properly.
Cross-Over
- The Cross-over splits the full range
audio signal into two, three, or four ranges to be delivered to
separate speakers. A 2-way speaker system consists of only a
tweeter and a woofer. A 3-way system consists of tweeter,
midrange, and woofer. And, a 4-way system consists of tweeter,
midrange, woofer, and sub-woofer.
There are two ways that the Cross-over can be connected: either
after the amplifier or before. Most low to medium power speaker
systems connect the Cross-over after the amplifier. Frequently,
the Cross-over is inside the speaker cabinet. High power speaker
systems often use a Cross-over connected before the amplifiers.
This also makes it necessary to have a separate amplifier for each
speaker. A 2-way system must be bi-amped (that is, 2 amplifiers).
A 3-way system must be tri-amped (that is, 3 amplifiers). If a
sub-woofer is used, it also requires a separate amplifier if the
Cross-over is connected in front of the amplifiers.
Sub-Woofer
- The Sub-Woofer reproduces extremely low
frequencies from about 100 Hz down to 20 Hz. These frequencies are
"felt" more than heard. The Sub-Woofer gives the bottom end "beat"
to music and the thunderous effects to movie sound tracks. If your
sound system is not used for music with a heavy beat or movie
sound tracks, then you may not need a Sub-Woofer.
Sub-Woofer may be placed wherever it is convenient since the human
ear cannot tell what direction bass sound comes from
Woofer
- The Woofer reproduces low frequencies from
about 500 Hz down to 100 Hz, the bass sounds. Speaker placement is
not critical because Woofers are omnidirectional.
Mirage
- The Midrange speaker reproduces midrange
frequencies from about 500 Hz to 6000 Hz. The midrange area
contains most of the sound for voices and instruments. Speaker
placement is more critical because mid-range sound is more
directional.
Tweeter
- The Tweeter reproduces high frequencies from
about 6000 Hz to nearly 20,000 Hz. It is responsible for the
brilliance in the sound, mostly associated with harmonics. Speaker
placement and angle are critical because high frequency sounds are
very directional.
Full Range
- A Full Range speaker is a single speaker
which attempts to reproduce the entire audio spectrum, usually not
as well as a multi-speaker arrangement. Full range speakers are
practical for low power speakers, but not for high
power.
Main or House Speaker System
- The Main or House
Speakers deliver the sound to the audience. Usually the a
combination of tweeter(s), mid-range(s), woofer(s), and possibly
sub-woofer(s) designed for smooth frequency response over a wide
frequency range and able to operate at high volume levels is used
for the Main or House Speaker System.
Usually, a central cluster is best for the main speaker system. A
number of multi-speaker cabinets are arranged in an arc and
suspended from the ceiling just in front of the center of the
performance area. The number of cabinets, angle of speakers, and
angle of cabinets is critical for even coverage.
If the room is not suited to a central cluster or the main system
must be portable, a distributed system with one or more
multi-speaker cabinets just in front of each side of the
performance area should be used. The height of the cabinets, angle
of speakers, and angle of cabinets is important for even
coverage.
A distributed system will experience the "comb filter"
effect to some degree. Each audience member hears sound from both
the left and right speakers. These sounds arrive at different
times and therefore are out of phase with each other. The amount
of phase difference depends on the frequency of the sound.
Therefore, from each individual audience seat, some frequencies
are louder (in phase) and some frequencies are quieter (180
degrees out of phase).
Monitor System
- The Monitor Speaker System is located
in or aimed at the performance area. Monitor speakers enable the
performer(s) to hear themselves and other necessary elements of
the program (i.e. music).
Usually Monitor speakers consist of a combination of a tweeter and
a woofer in a slanted cabinet designed to aim the sound back
toward the performers.
Monitor speakers should be placed to satisfy the performer(s).
Wedge shaped monitor speakers should be placed on the floor in
front of the performer so they aim the sound towards the rear of
the performer's mike. Sometimes side fill monitors are needed to
cover a larger area (i.e. if the performer moves around). Avoid
placing monitor speakers where they face the front of a
microphone.
If multiple monitor mixes are required, each performer may have
their own monitor speaker(s).
