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NOTES ON ADJUSTMENTS
1. Turn the EQ controls on the mixing desk to a central position (linear setting).
2. Switch any third-octave or octave equalisers to “Bypass” or set the equaliser controls to a
central position.
3. Connect a microphone and use the SUB and TOP control of the power amplier to set the
signal in such a way that the human voice sounds “natural”.
4. This concludes the basic system setup.
5. Using the EQ controls, a wide variety of microphone and instrument inputs can now be
adjusted on the mixing desk to match personal preference.
EQUALISER
Third-octave or octave equalisers should be set very carefully, if at all. With many third-octave or oc-
tave equalisers, even slight alterations in Lo or Mid range lead to unacceptable sound falsications
which cannot be eliminated via other EQ controls.
ADJUSTMENTS WITH REAL TIME ANALYSER AND EQUALIZER
“Fine tuning” of amplier and loudspeaker systems with real time analysers and third-octave or octave
equalisers is not normally advisable. Depending on the setting in question, third-octave equalisers in
particular cause phase and group time distortions which falsify the sound considerably. The measuring
microphone evaluates both the cabinet direct sound eld and the reections simultaneously, thus pre-
venting any proper interpretation of the readings from a sound point of view.
If particularly unfavourable acoustic conditions make ne tuning seem necessary, the following princip-
les should be adhered to when tuning amplier and speaker systems:
1. Only measure in the direct speaker sound eld, normally at a distance of 3 - 5 metres
maximum. If the measuring microphone is set up further away, (e.g. in the middle of the
hall), both direct and room sound is measured. Any attempt to linearize this “blend” with EQ
normally produces an extremely mid-, tinny- sounding, obtrusive sound image.
2. When measuring in the “critical” range between ca. 250 Hz - 5 kHz, only cut with the EQ - do
not boost on any account! A “gap” in the spectrum is not considered so obtrusive as a “hump”.
It is essential to avoid substantial increases in the bass range as this would drastically impair
the transient response of the entire system.
3. When measuring, only work with 5 W maximum capacity (pink noise). This prevents
amplier clipping and related distortions. With conventional noise generators the peak value of
the noise voltage is approximately 10 dB higher than the RMS value, meaning that even 5 W
amplied power can lead to short-term peaks of up to 50 W.
4. Dominant acoustic feedback can sometimes be suppressed somewhat by third-octave
equalisers or parametric EQ’s. In applications of this nature, great care should be taken to
ensure that the gain in volume does not mean reduced clarity and naturalness.
NOTES ON ADJUSTMENTS
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