Behringer MDX4400 User Manual
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MULTICOM PRO MDX4400
1.1.3 Compressors/Limiters
By measuring the dynamic range of musical instruments in live recording situations, you will find that extreme
amplitudes occur which often lead to overload in subsequent signal processing equipment. Especially in
broadcasting and record cutting techniques, these signal peaks can lead to heavy distortion. To avoid this kind
of distortion or, for example, to avoid loudspeakers being damaged by overload, compressors or limiters are
used.
The principal function used in these devices is dependent on an automatic gain control as mentioned in the
previous section, which reduces the amplitude of loud passages and therefore restricts the original dynamics
to a desired range. This application is particularly useful in microphone recording techniques, to compensate
for level changes which are caused by varying microphone distances. Although compressors and limiters
perform similar tasks, one essential point makes them different: limiters abruptly limit the signal above a
certain level, while compressors control the signal gently over a wider range. A limiter continuously monitors
the signal and intervenes as soon as the level exceeds a user-adjustable threshold. Any signal exceeding this
threshold will be immediately returned to the adjusted level.
A compressor also monitors the program material continuously and has a certain threshold level. With com-
pression, in contrast to the action of a limiter, signals are not reduced in level abruptly once the threshold has
been exceeded, but are returned to the threshold gradually. The signal is reduced in gain, relative to the
amount the signal exceeds this point.
Generally, threshold levels for compressors are set below the normal operating level to allow for the upper
dynamics to be musically compressed. For limiters, the threshold point is set above the normal operating level
in order to provide reliable signal limiting, to protect subsequent equipment from signal overload.
1. INTRODUCTION