Symetrix 258E, Руководство пользователя, Страница: 32 / 46

528E
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the equalizer. Likewise, cutting or attenuating certain frequencies desensitizes the compressor to
those frequencies.
Keep in mind that the C
OMP
T
HRESHOLD
becomes a function of the amount of overall gain through
the equalizer, including the boost. This technique can be used with any frequency that can be
controlled by the equalizer.
Using Sidechain EQ to Enhance Expander Action
Since the expander can only discriminate between different levels (not different sounds), it can be
fooled by signals whose levels are nearly the same, even if the frequency content of those signals is
fundamentally different. When the 528E’s expander is used to shut out unwanted sounds, any
signal that exceeds threshold will trigger the expander. When unwanted signals trigger the system,
it’s often possible to eliminate the false triggering by equalizing the control signal.
For example, if low frequency signals transmitted through a desk or podium are triggering the
528E’s expander unnecessarily:
With an equalizer in the sidechain, remove the low frequencies from the control signal, and/or
boost the higher voice range frequencies.
When the offending frequencies are removed, and the relative level of the desired frequencies is
increased, the expander can tell the difference between the wanted and unwanted signals. Use this
technique in any situation where levels are nearly the same, but the fundamental frequencies
involved are different.
Note The ability of the expander to discriminate between wanted and unwanted signals is
determined in part by mic technique. Be particularly careful of high frequency sounds
entering the side or rear pattern of a cardioid mic. Most cardioids exhibit a sharply rising
off-axis response characteristic at higher frequencies. Check the off-axis curve (the lower
one) in the manufacturer’s literature. If there’s only a 3dB to 6dB difference between the
on-axis (front) response and the off-axis (side or rear) response in the 5kHz to 10kHz
region, high frequency sounds will be picked up by the side or back of your mic.
Use the mic’s directional pattern to keep other sources as far off-axis as possible - do
everything you can to extract all the source-to-source discrimination possible through
good mic technique. The sounds picked up by individual mics must be primarily the
sound of the desired signal, or the expander won’t be able to tell the difference.
Using Reverb or Effects
Effects usually require another mixer input for effects return. However, the 528E’s patching
connections can be used to feed a signal to the effects unit, and the output stage input can be used
to return the effects signal to the 528E’s output. The only requirement is that the effects device
have a mix control to set the direct/effects signal mix. If you need a hookup diagram, you’ll find
one in Figure 7-4.
Vocal Processing - Recording and Reinforcement
The 528E handles a wide variety of program material with ease. When recording vocals, the
undesirable side effects that usually result from high ratio comp/limiting, like headphone leakage
and room noise, can be reduced with the 528E’s interactive expander processing. During
mixdown the 528E not only provides compression, but also eliminates the noise that often accom-
panies vocal tracks that are processed with high frequency EQ, compression, or both.
In sound reinforcement situations, if the threshold has been set correctly, the expander will
attenuate whenever a mic is not in use, eliminating extraneous pickup of stage sounds, and reduc-
ing feedback from monitor speakers. The operating principle is the same for both the recording
and reinforcement situations.