Basic Mixer Operation; Equalizer Functions - Shure SCM800 User Manual

1. Turn on the Power switch.
2. Adjust each channel level so that its Overload LED flickers only
during very loud speech or noise.
3. Turn unused channel controls full counterclockwise.
4. Adjust the Low-Cut and High-Frequency controls adjacent to
each Input Gain control until all microphones sound alike.
LIMITER
The SCM800's output limiter prevents distortion during loud program
peaks without affecting normal program levels. Increasing the individual
or Master level controls will increase the average output and, in turn, the
amount of limiting. The limiter prevents excessive overloading of devices
connected to the SCM800 output. As supplied, the limiter is defeated.

EQUALIZER FUNCTIONS

Low Cut Filter (High-Pass)
The low-cut (or high-pass) filter allows all frequencies above its cutoff
point to pass from filter input to filter output without attenuation, while fre-
quencies below the cutoff are attenuated (see Figure 9). The cutoff point
is defined as the frequency where the signal has dropped 3 dB relative
to the flat, or bandpass, region. Below the cutoff point, the filter exhibits
increasingly more attenuation as the frequency diminishes. The rate at
which this attenuation occurs is defined in decibels per octave (dB/oct).
The SCM800 has a one-pole, low-cut (highpass) filter of 6 dB per octave.
Low-cut filters are ideally used for attenuating, or rolling off, the audio signal
where extraneous noise, excessive proximity effect, or other unwanted
material is present. For example, the low-frequency vibration cause by
footsteps and vehicle traffic can be transmitted through microphone
stands to the microphone, and then into the sound system. These
frequencies, typically ranging from 5 to 80 Hz, are generally not desirable.
+2
FULL CW
0
-2
-4
-6
-8
50%
ROTATION
-10
20 100
LOW–CUT FILTER EFFECTS

BASIC MIXER OPERATION

FULL CCW
1,000
FREQUENCY (Hz)
FIGURE 9
5. Adjust the SCM800 Master level control for the desired output
level, as indicated by the output peak meter.
6. Adjust the headphones volume level with the PHONES control
knob.
The limiter threshold can be set for a peak output level of +4, +8, or +16
dBm. With the threshold set at +16 dBm, the mixer has 12 dB of head-
room at a nominal level of +4 dBm. Refer to the Internal Modifications
section for information on how to change the limiter's settings.
High-Frequency Shelving
The fixed-frequency equalizer produces a 6 dB boost or cut at 5 kHz
and above (see Figure 10). High-frequency shelving is extremely useful
for boosting flat frequency response, tempering very sibilant vocal
microphones, or enhancing the sound of off-axis lavalier microphones.
+10
+8
+6
+4
+2
0
-2
-4
-6
-8
-10
200
HIGH-FREQUENCY SHELVING EFFECTS
5,000
7
1,000 10,000 20,000
FREQUENCY (Hz)
FIGURE 10
FULL
CW
50%
ROTATE
FULL
CCW