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Refer to General Operating lnstructions for connec-
tions and setup.
Use typical program source and program material.
Locate listening position in main audience area so
that what is heard is typical of what most of the
audience will hear. If practical, the SR107 should
be at this location (temporarily) for ease of ad-
justment.
As Filter Control adjustments are made, adjust
LEVEL Control to maintain initial volume level, using
EQUALIZER INIBYPASS Switch to compare equal-
ized to unequalized sound level and quality.
Bass guitar, string bass or kick bass drum sounds
are most affected by 63 Hz and (to a lesser degree)
125 Hz Filter Controls. Avoid excessive boost of
these frequencies or low-frequency overload may
occur.
Power supply hum (60 Hz) and certain types of
turntable rumble may be suppressed using 63 Hz
Filter Control. The 31 Hz Control may also be help-
ful for very low frequency turntable sounds.
The 8 kHz Filter Control is most effective in con-
trolling "brightness" of the sound, especially affect-
ing speech sibilance and cymbal sounds. The 8 kHz
and 16 kHz Filter Controls may also be used to
reduce record noise and tape hiss.
Vocal performer sound is affected most by varia-
tions in the Filter Controls covering the 1 kHz to
4 kHz range.
If room resonance is encountered where frequen-
cies in a certain band are accentuated, some ad-
justment of speaker positions may correct the
condition. If this is not practical, experiment with
attenuation of the octave bands in the suspect fre-
quency
region. The low-frequency octaves (32
through 250 Hz) are often affected by room char-
acteristics. A typical subjective effect is that of a
"boomy bass" sound.
Use tone controls on the console or mixer (if so
equipped) for broadband adjustment of the high
or low end of the audio spectrum.
Live Performance Equalization
Equalization of a sound reinforcement system for live
entertainment applications is similar to that described in
Playback Equalization except that microphones and per-
formers constitute the sound source. Utilize this section
where applicable in live performance equalization.
In most indoor sound system installations, the SR107
Audio Equalizer is adjusted first for feedback control as
previously described. Additional adjustments may then
be made to improve sound quality. This second level of
adjustment is usually performed during a rehearsal where
the performers and musicians are present and the sound
aspects of the total performance can be evaluated. It is
important to note that this secondary equalization process
can affect the feedback threshold previously achieved
and should therefore be performed with caution.
If the SR107 was not previously connected to the sound
system, refer to General Operating lnstructions for con-
nection and setup instructions. Preliminary adjustment of
the Equalizer can be made using recorded program
material typical of the live performance.
The recommendations given in Playback Equalization
should be considered along with the following:
1. While judgements of sound quality should be made
in the main audience area, it is advisable to check
a number of locations throughout the area for
significant variations in response. If such are en-
countered, speaker location and aiming should be
reviewed.
2. Any increase in Filter Control setting (clockwise
rotation) previously adjusted for feedback suppres-
sion should be done with care. In the case of a
reverberant room where an audience would signifi-
cantly increase the sound absorption, this may be
possible.
3. Intelligibility and presence for vocal performances
may be improved by slight increases of system
response in the 1 kHz to 4 kHz region.
4. Adjustment of the response of a particular micro-
phone must be made through the use of the console
or mixer tone controls for that particular channel.
If an individual channel exhibits a "hollow" or un-
natural sound, the gain of that channel may be
near feedback threshold and should be reduced.
5. If the room is acoustically "dead" (carpeted, up-
holstered seats, acoustic wall treatment), the sound
system output may seem deficient in the lower mid-
range frequency region. In this case, slight boosting
of the frequency bands in the range of 1 kHz to
4 kHz is appropriate. If the room is "live" or rever-
berant, the sound may seem excessively "bright"
and some attenuation of the octave bands at 8 kHz
and 16 kHz may provide a more uniform response.
In outdoor applications, attenuation of both low and
high frequencies may be experienced. Boosting
octave bands 125 Hz and below, 8 kHz, and 16 kHz
may be helpful but must be performed carefully to
avoid excessive amplifier and speaker drive levels.
6. Occasionally a combination of program material
and room resonance produces a "boomy" sound in
which some low frequencies are accentuated. At-
tenuation of the 63, 125 or 250 Hz Filter Controls
will suppress this characteristic.
Equalization Instrumentation
While the final measure of any equalization effort is a
subjective judgement of the quality of the sound delivered
to the audience, acoustic measurement instrumentation
is available which can be of considerable assistance in
more efficient and consistent equalization procedures.
The equipment consists of a pink noise generator
(equal sound energy per octave), an equalization analyzer
and an omnidirectional analyzer microphone with a
known frequency response. The analyzer generally pro-
vides a display of input signal amplitude versus frequency
in either octave or
1/ 3
octave bands for the complete
audio spectrum.
In general, equalization analyzer equipment is used to
measure sound system performance instead of perform-
ing the subjective evaluations previously discussed. Con-
nection, setup and operation of the SR107 remains the
same. Recommendations regarding various equalization
objectives are also generally applicable. Operation of the
analyzer equipment is in accordance with the manufac-
turer's instructions.
Usually, the analyzer equipment is used first to estab-
lish the desired house curve or preferred sound system
response characteristic. For playback equalization, the
analyzer microphone is located in the main audience
area and connected to the equalization analyzer input.
The noise generator is connected to the audio console
or mixer input and the volume adjusted to provide a
sound level sufficiently above the room ambient noise
level. The analyzer should be placed close to the SR107
so that as Equalizer adjustments are made, the results
are easily observed. Adjustment for a flat response in the
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