Here is a common complaint made by the owner of a
damaged loudspeaker: "How could I have blown a
loudspeaker? I have a compressor!" Unfortunately, while
compressors and limiters help prevent audio transients
from causing clipping or possibly damaging a loudspeaker,
high-level transients are not the only cause of damaged
loudspeakers. In fact, over-compression of the audio signal
can contribute to premature loudspeaker failure.
It is standard practice to use an amplifier with a power
rating at least twice the loudspeaker’s continuous power
rating (e.g. use a 200 watt amplifier for a 100 watt
loudspeaker). The extra headroom afforded by the larger
amplifier allows for peaks in the program material to be
delivered to the loudspeaker without clipping. The majority
of the amplifier power goes largely unused since the
average level of an uncompressed audio signal is
considerably lower than the peaks. Highly compressed
signals have an average level much closer to the peak
level. If the level of the compressed signal is raised to take
advantage of the additional amplifier power (thereby
making it louder for the audience), the average power
delivered to the loudspeaker may be more than the
continuous power rating of the loudspeaker, overheating
the loudspeaker’s voice coil and causing failure.
As with all audio processors, using a compressor
does not eliminate the need for proper system operation.
Though a compressor or limiter is essential for reducing
transient peaks, excessive compression is the enemy of
the loudspeaker.
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