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6.2 The COMPOSER PRO as a protective device
Sound system distortion is usually a result of amplifiers and loudspeakers being driven beyond their limita-
tions by signals clipping. The signal limitations that occur lead to unpleasant distortion that is dangerous to the
speakers.
A speaker diaphragm is required to accelerate, slow down, smoothly change direction and accelerate again in
normal operation. Distorted operation (clipping) leads to instant acceleration, instant stop, change of direction
and instant acceleration again. Since speaker diaphragms are subject to the laws of physics, they will not
take this kind of punishment for long: the diaphragm will either break up or its voice coil may overheat.
In addition to the damage caused by sustained overload, the speaker may also be damaged by an occasional
high level overload, e.g. the sound of a microphone falling onto a hard floor. Even if this type of transient does
not destroy a speaker outright, it may damage the speaker surround in such a way, as to cause mechanical
abrasion and future failure. It is recommended that you use the Behringer COMPOSER PRO in order to
protect the speaker. Brick Wall peak limiters are not normally necessary for PA systems, as amplifiers and
loudspeakers are tolerant of short signal peaks.
Nevertheless, conventional limiters have to be generally driven far beyond the headroom limit of an amplifier,
in order to limit the level and length of the transients responsible for overloading the system. The disadvantage
of this principle is that the units full range cannot be completely used. If an increase in the average level of up
to 3 dB is attained with the COMPOSER PROs IGC Peak Limiter, this means that you effectively double the
power amplification. The COMPOSER PRO can act in this way to convert a PA system of 5,000 Watts into a
distortion free 10,000 Watts system. The following instructions will help you to integrate the unit into your
system.
6.2.1 Protection Of A System With A Passive Crossover
If your sound system incorporates a passive crossover network (included in the loudspeaker case), insert the
Behringer COMPOSER PRO between your mixing console output and the power amplifier input. It is used as
the last link in the chain preceding the power amp. Thus, you can effectively avoid the technical knockout of
the midrange/tweeter range caused by high-energy bass signals! This statement, as paradox as it may seem
at first, can be explained with the fact that especially low-frequency signals with high amplitudes can overload
the power supplies in the amplifier(s). The resulting clipping (cutting off of signal peaks) produces high-
energy distortion (upper harmonics), which is abruptly added to the midrange/tweeter signals. For this reason,
weak power amps, in particular, must be protected by a limiter in their input dynamics.
6.2.2 Protection Of A System With An Active Crossover
For systems using active crossovers, there are two ways to use the Behringer COMPOSER PRO. The unit
may be inserted between the console output and the crossover input. In this application, the Behringer
COMPOSER PRO will process the entire audio frequency spectrum.
Alternately, the Behringer COMPOSER PRO can be inserted between the output of an active crossover and
the input of a power amplifier. In this application it will only affect a specific range of frequencies. This
application is particularly suited to protect the most fragile components of a multi-way speaker system against
harmful signal peaks. For example, when your tweeters keep on going up in smoke all the time, the entire
system should be operated at lower sound pressure levels or the tweeters should be replaced by other
models. Using the COMPOSER PRO in the corresponding tweeter band avoids overloading and thus damage
to the speakers.
6.2.3 Improving The Sound Of A Processor System
A processor system is understood as a PA system which contains a special active crossover whose outputs
are linked via separated power amplifiers to the loudspeakers. Each band has its own limiter whose task it is
to limit dangerous signal peaks to a certain level. This process avoids overloading the subsequent power
amplifier or destruction of the loudspeaker.
In some units, the crossover frequencies in the crossover unit are further changed during high signal levels
to achieve a loudness contour suited to the human hearing. But in many cases, this function leads more to
a disturbance than to an improvement of the sound quality.
6. SPECIAL APPLICATIONS
