Yamaha EM1620 - Manual (Page 9)

CHANNEL EQ GRAPHIC EQUALIZATION
The HIGH, MID and LOW equalization controls on each
channel of the mixer make it possible to independently
equalize the channel signals to some degree. The basic
rule of thumb is that equalization should NOT be used
unless it is absolutely necessary. Always put some effort
into proper microphone selection, careful microphone
placement, and/or setting of source instrument controls
to achieve the desired sound before resorting to equali­
zation. When you've set everything up as best you can,
but still need to modify a sound, then go ahead and
equalize. Channel EQ can be most useful in tonally sepa­
rating one sound from another or from a group.
A bit of extra HIGH EQ added to a guitar sound, for
example, can give it a bit more "bite" and help it to stand
out more clealy from the background. Vocals tend to
stand out nicely if given a bit of boost in the MIDDLE
range. Speech generally benefits from a reduction in the
low frequencies—to prevent that "boomy" sound that
occurs when the speaker gets too close to the micro­
phone. Experimentation and experience will tell you how
much EQ is right for different types of sound.
HiGH
EQUAUZER
MID
EQUAUZER
LOW
EQUAUZER
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Graphic equalization has two main uses in powered
mixers like the EM1620: compensation for acoustic de­
ficiencies in the listening area; and feedback control.
Like the channel equalizers, the graphic equalizer should
be left alone unless it is absolutely necessary. The more
equalization you use, the more phase deviation you in­
troduce into the program signal, and this can result in an
unnatural sound. There are many instances, however, in
which the listening area itself causes response anoma­
lies due to its acoustic characteristics. Large areas of
uncovered glass or tiled floors, for example, are ex­
tremely effective reflectors of high-frequency sound.
Sound produced in environments like this can sound
painfully sharp, and some reduction in the high fre­
quency range may be called for. Smaller symmetrical
rooms (a square room being the worst case) can actually
have resonant frequencies within the audible low-fre­
quency range. A bit of reduction in the low frequencies
can help to make the sound more intelligible. Note that
in almost all cases good equalization practice demands a
cut in the offending frequency range rather than a boost
in ranges where response is lacking.
The graphic equalizer can also be used—although to a
limited degree—for feedback control. Proper micro­
phone placement is the primary tool for prevention of
feedback, but this can be extremely difficult if you're
working in a tight stage area. Simply cut response in the
frequency range where the feedback is occurring (this
wil have to be found by experimentation). This will
compromise the overall frequency response of the pro­
gram, but it's better than facing the possibility of squeal­
ing feedback in the middle of an important performance.
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