with a loud musical signal, but leave some dB headroom for
unexpected level peaks. However, don't worry if the 'Peak' LED
flickers shortly from time to time at the very loudest passages,
as the GF equalizer still offers some headroom above clipping
indication.
In a studio environment, where precise fine-tuning of sounds by
ear is required, it can also be a good idea to set the gain con-
trol, so that the output loudness of the equalizer is the same in
'EQ on' and bypass mode, helping the user to A/B-compare his
equalized sound with the original signal.
General rules for equalizing
In the first place, changing of EQ settings should always be
done carefully and slowly to avoid the danger of annoying if not
hazardous feedback surprises. If you are using your ear as a
reference, bear in mind that the human ear adapts to the new
sound curve and accepts it as a new reference. Therefore, it is
always a good idea to compare the equalized sound with the
original signal from time to time to avoid over-equalization,
which will result in a rather unnatural sound. Instead of boosting
a certain frequency band, first try to achieve the same effect by
attenuating other frequencies, as this generally results in a
more natural sound.
Room equalization
Most acoustical environments, especially rooms, tend to over-
emphasize, or more likely, 'swallow' certain frequencies for phy-
sical reasons. To achieve a linear sound reproduction in spite
of this phenomenon, a graphic equalizer can be used to cut or
boost these suspicious frequencies. First, a real-time analyzer
should be used to detect holes or peaks in the room's frequen-
cy response, which can then be compensated for by the equali-
zer, until the analyzer displays a linear frequency curve. The
sound system is now tuned to the 'house curve' of this particu-
lar room. The following illustration shows, how the analyzer and
equalizer have to be set up for room equalization.
Feedback elimination
If the gain of a sound reinforcement system with microphones
is constantly increased, at some point feedback will occur.
Monitor systems are especially sensitive to feedback due to
their position near microphones, especially when angled
towards them. As a rule, feedback starts at one single frequen-
cy, which can be determined by an analyzer or with the help of
a musical instrument and the table on page 13. Reducing the
gain of this particular frequency on the equalizer will stop the
feedback and allow the overall gain of the system to be raised,
resulting in a higher sound pressure without feedback. When
the next frequency starts to feed back, this procedure can be
repeated to achieve even more feedback-free amplification.
Recording
- Simulated stereo: a simulated stereo signal can be created
from a monaural signal by routing the signal through both
channels in parallel. Boost and cut alternate bands on chan-
nel A and, in reverse order, on channel B and have the chan-
nels panned left and right in the mix.
- Noise reduction: hiss on cassette recordings can be reduced
by boosting all frequencies above 6.3 kHz when making
recordings. When playing the tape back, cut the same fre-
quencies on the EQ for the same amount, resulting in less
hiss. Old but proven effect devices can be improved in their
noise behaviour almost the same way: route the input of the
effect device through channel A and the output through chan-
nel B. Boost the highs on channel A and cut the same fre-
quencies on channel B.
GF equalizers owner's manual
16
owner`s manual GF equalizers © 1994 Zeck Audio
Analyzer
Mixing desk
GF 215
Constant
Q
2x15 Graphic EQ
-10
+10
0
Gain
Channel 2
Power on
EQ in
Low cut
-10
+10
0
Gain
Channel 1
EQ in
Low cut
25
40
63
100160250400630
1k
1.6k2.5k
4k
6.3k10k16k
25
40
63
100160250400630
1k
1.6k2.5k4k
6.3k10k16k
25
40
63
100160250400630
1k
1.6k2.5k
4k
6.3k10k16k
25
40
63
100160250400630
1k
1.6k2.5k4k
6.3k10k16k
+12
0 dB
+6
+3
+9
- 3
- 9
- 12
- 6
Clip
3 dB
6 dB
12 dB
Signal
H
E
A
D
R
O
O
M
Clip
3 dB
6 dB
12 dB
Signal
H
E
A
D
R
O
O
M
R
power
AP ·1800
2 x 900 W att Ster
eo Power Amp
Protect
Limit
Level
ch 1
54
48
45
42
39
36
33
30
27
24 2118 15 12
9
6
3
0
51
∞
5760
– dB
Protect
Limit
Level
ch 2
54
48
45
42
39
36
33
30
27
24 2118 15 12
9
6
3
0
51
∞
5760
– dB
Power
Master
Out
L
L
L
R
R
R
Input
Power amp
GF 215 / GF 230
Input
Output
Output
Measuring microphone
