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1kHz pure tone just below clip level
(Vertical = level in decibels, horizontal = frequency)
1kHz heavily clipped signal
The heavily clipped signal (see previous illustration) shows clipping distortion as a series of odd harmonics
at 3kHz, 5kHz, 7kHz etc., whose levels decrease with frequency at approximately 6dB per octave. Where
clipping occurs before the system crossover, clipping harmonics can crossover into the HF driver and the
HF driver can be called upon to dissipate far more power than normal.
Note that the example shows a single frequency fundamental. Musical signals will be a lot more complex
and the distortion content will be denser. Asymmetrical clipping (from studio or backline valve amplifiers,
for instance) would also include even harmonics.
As mentioned earlier, long-term clipping can be avoided – and performance improved - if you choose
mixers, effects units, controllers and amplifiers with adequate headroom and set your limiter thresholds
to below clipping levels. You can also avoid clipping your signals at source by setting your console and
effects system “gain structure” carefully. See appendix B...
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