3. PINK NOISE RUN-UP:
Turn down the mixer output controls before switching on the Pink Noise, so that you don’t
detonate your speaker cabinets. Now switch the PINK NOISE button IN on the RE 27 and turn up the mixer and EQ LEVEL
controls slowly until you hear pink noise through the speaker(s). There is a Pink Noise Output Level Adjustment on the rear
of the RE 27 - use a 1/8" screwdriver to vary the amount of pink noise to the mixer if necessary.
4. MICROPHONE PLACEMENT:
You should perform the pink noise test
with
at least
two different test microphone
locations
for each separate channel of EQ. Since speaker dispersion characteristics can vary greatly, it is desirable to look at
a couple of different areas with the mic to obtain an average for the entire listening area. If you are using one equalizer
channel for both speakers (mono), place the mic in the center of the left half of the listening area and adjust for green LEDs
with pink noise through the left speaker. Now move the mic to the center of the right half of the listening area, run pink
noise through the right speaker and observe the analyzer LEDs: use the RTA LEVEL control to center the response for as
many green LEDs lit as possible. For each frequency that requires a different adjustment than the left channel, note the
original setting of the slider, then adjust it so that the green LED above it is lit and then note this new slider position: the
final setting should be half-way between these two slider positions, resulting in an average response for the left and right
channels. If you are running stereo, use two mic locations for each channel, averaging in the same manner if there are
differences.
An RE 27 can be used as a driver alignment tool (see the AC 22/23 Owners Manual) as well as a room-flattening equal-
izer. Drivers are aligned when maximum level is shown at the crossover frequency on the RE 27 display. It is important to
align drivers either physically or electronically in multi-way systems for the best sound. The mic should be at listener-ear
height relative to the center of the driver stack If a clear sound is desired in the back of the hall, the height of the RE 27 mic
should be in line with the on-axis phase response of the speaker stack, perpendicular to the drivers as shown below.
5. ANALYZER SETTINGS:
Select either NORMAL or HOUSE CURVE on the RE 27 display. NORMAL is generally
used for large concert halls, large theaters and outdoor facilities. Use the HOUSE CURVE for smaller concert halls, lounges,
churches, etc. In this mode the analyzer is modified requiring that all sliders between 400 Hz and 1.6 kHz must be attenuated
-3 dB in order to obtain green LED response (this is most easily seen in the ±l dB mode). This results in a warmer sound
quality at lower sound pressure levels, requiring less additional adjustment after the pink noise test.
Now select either the ±3 dB or the ±l dB WINDOW on the analyzer. We recommend starting with the ±3 dB setting, then
switching to the ±1 dB mode for fine-tuning frequencies above 400 or 500 Hz. The crest factor (peak response) of true pink
noise causes considerable LED flutter in the ±1 dB mode below about 500 Hz, thus it is more expedient to use the ±3 dB
setting for these frequencies.
6. INITIAL SYSTEM ALIGNMENT:
Before using the equalizer for adjustment, use the analyzer to align other equip-
ment in the system (EQ should always be a last resort after you’ve corrected response problems everywhere else). With all
EQ sliders flat (centered) adjust the electronic crossover frequencies and level controls (if used), passive crossover controls,
speaker placement and alignment, etc. to get as many green LEDs lit as possible on the display. Only after this is done
should you use the equalizer sliders to flatten the system (see next step).
7. EQUALIZER SLIDER ADJUSTMENTS: Now
adjust each slider up or down as necessary until the green LED
above it is lit; if the red is lit, move the slider down until green comes on. If yellow is lit, move the slider up to obtain green
If you can’t get one or more green LEDs lit with their sliders fully boosted or cut, make a slight adjustment in the pink
noise volume or RTA LEVEL control to get these bands in the green. Then re-adjust the remaining sliders. You will also
notice that adjusting one slider may affect the LED readings on the adjacent bands: this is due to the presence of frequencies
half-way between the two bands, which will be affected by both sliders. Not to worry: simply nudge the adjacent slider until
the green LED lights up again.
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