Equalizing The Main Speakers Of A Standard Reinforcement System - DOD RTA Signal Processors Owner's Manual

Signal Processors 18-0121-B 6/8/99 10:24 AM Page 7
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characteristics vary greatly as you move around the room (particularly with
multiple driver systems). If you find that different areas of the room behave
differently, try to average the settings on the equalizer to correct the room as
a whole.
You don't need to blast the system with pink noise. Use just enough level
from the RTA to overcome any ambient room noise (such as air conditioners
or traffic noise). The sensitivity of the RTA should be just high enough that
when you turn the pink noise off, none of the LEDs are lit by the noise in the
room.
Use the 3 dB resolution setting on frequencies below 500 Hz. Peak response
of the pink noise causes drift in the 1 dB resolution setting, making it hard to
correct quickly. Use the 1 dB resolution setting to measure frequencies above
500 Hz.
EQUALIZING THE MAIN SPEAKERS OF A STANDARD REINFORCEMENT SYS-
TEM
First, place the calibrated microphone 3 to 4 feet in front of the main speak-
ers on the axis of the speaker. This is especially important with an indoor sys-
tem so that you make the first adjustments to the system inside this critical
distance (before the reverberation of the room environment has a chance to
affect the response of the system).
Turn on the pink noise generator, being careful not to blast the system. Make
sure that you turn down the input to the system, then increase the pink noise
level to a listenable measuring level. Using the graphic equalizer, adjust the
response of the system to be as flat as possible.
Once you have equalized and corrected the system in the near field, move the
calibrated microphone out into the room, a normal listening distance from the
speakers. As you move the microphone away from the speakers, you will
notice two things:
1. The high frequency response of the system will fall off, usually starting at
about 10 kHz.
2. When there are other structures nearby, one or more peaks or dips will
appear in the low end.
The high frequency rolloff is caused by absorption of high frequencies in the
air. Don't adjust the highs any more by measurement. The highs can be
adjusted by ear using program material you're familiar with. Be sure to check