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Clipping
and driver failure:
Clipping means
that the tops of the signal are "clipped off" or
"flat-topped" when the signal level is exceeding the
maximum capability of the power amplifier or some other piece of
equipment in the system. During the times when a signal is flat-topped,
loudspeaker cones are not being "instructed" to move as it
is receiving essentially a DC signal. This means all power goes into
heating up their voice coils instead of producing sound. In other
words, during the times the signal is flat-topped a loudspeaker is
100% efficient at converting power into heat. Ironically, the more
efficient the driver, the worse the problem. A horn tweeter (~25%
efficient) normally converts 75% of its input power to heat. During
clipping it must convert 25% more power to heat. A cone woofer (~3%
efficiency) normally converts 97% of its input power to heat. During
clipping, it has to convert a mere 3% more to heat. Now you know why
tweeters burn out much more easily.
Thermal
Inertia:
A hidden
consequence of clipping is that, while high frequency drivers are
more efficient in converting electrical power to sound, they have
less mass than low frequency drivers. Mass translates into thermal
inertia. The higher the thermal inertia the more it takes to change
the temperature of the mass. This means that high frequency drivers
can heat up faster than low frequency drivers. This is especially
true during clipping because the driver is converting all its input
power from the amplifier into heat while the signal is clipped.
Clipping Facts:
ANY CLIPPED SIGNAL
CAN BLOW A LOUDSPEAKER. It does NOT matter if it is caused by the
mixer, amplifier OR any other piece of equipment in the system OR
whether the amp is at full output.
A MAJOR CAUSE OF
DRIVER FAILURES is using too small an amplifier. If the amplifier is
driven into clipping, it can burn out a loudspeaker that has a power
rating HIGHER than the amplifier.
CLIPPING CANNOT BE
DETECTED by electronic or built-in loudspeaker protection circuits
and therefore cannot prevent damage from clipping.
LOUDSPEAKER POWER
RATINGS are valid on for un-clipped input signals.
WATCH THOSE CLIP
INDICATORS on every piece of equipment to avoid ANY clipping.
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