Rane RA 27 User Manual

Page 6

Manual-5

MONITORING PROGRAM MATERIAL FOR FEED-
BACK USING THE DISPLAY

Once the pink noise test is completed, switch off the PINK

NOISE on the RA 27 and unplug the Rane test mic from the
front panel jack. When the mic is unplugged, the display is
automatically switched to monitor the signal at the RA 27
LINE INPUT jack on the rear. Adjust the LEVEL control so
that an occasional green LED blinks on during the perfor-
mance peaks, but no red LEDs come on: you should be in the
±3 dB mode on the display. If feedback occurs, one or more
red lights show the general feedback frequency area. Usually
several red LEDs will be lit by the time you quickly cut back
volume to kill the feedback and glance at the display. When
this happens keep watching the display: the last red LED to
go off contains the exact feedback frequency (it was the first
LED on, too, but you probably didn’t see it). Adjust that
slider down a couple dB and feedback problem will be
reduced. If you’re real good you’ll keep one eye on the
analyzer display and quickly adjust one or two sliders when
feedback occurs, without altering master volume levels. This
program monitoring feature is particularly useful for stage
monitors which are usually plagued with feedback problems.

TESTING

The RA 27 really contains its own test equipment. By

patching the PINK NOISE OUPUT to the LINE INPUT with
a mono ¼" patch cord (and no mike plugged in) the entire
analyzer/pink noise system can be checked and verified. Turn
up the LEVEL control until the display LEDs respond. With
all sliders centered, the display should show all green in the
±3 dB position with proper level settings. Switching to ±1 dB
should show mostly green with some LED flutter in the lower
frequency bands below l kHz (due to inherent crest factor of
pink noise showing through the 2 dB window).

STAGE MONITOR EQUALIZATION

IMPORTANT NOTES:
1. Analyzing and equalizing the monitors provides the most

expedient method to optimize stage monitor sound quality
and reduce feedback problems. The stage mic is connected
to the same mixer as the RA 27. Feedback induced by
specific stage mic/monitor speaker coupling can also be
attenuated by leaving the stage mic turned up and running
up the pink noise level through the monitor speaker until
feedback occurs. Attenuate each feedback frequency, as
indicated by the analyzer display, until the mic/monitor
combination feeds back at two or more frequencies
simultaneously. Usually the final EQ setting will be a
compromise between a good monitor sound that doesn't get
as loud, or a not-so-good monitor sound that gets louder
before feedback.

2. Place the Rane microphone at eye level of the performer

and about six inches off to one side of the stage micro-
phone, in line of sight to the monitor speaker. If the stage
microphone is directly between the Rane mic and monitor
speaker (blocking line of sight), some high frequencies will
be blocked giving a false reading on the analyzer display.

3. If you are running more than one monitor from a single

equalizer, test each monitor location by running up pink
noise until feedback occurs. The monitor which feeds back
soonest should be used for the overall EQ adjustments
using pink noise.

4. If maximum SPL before feedback is most important, use

the stage mic only. This arrangement allows the analyzer to
look at the specific relationship between each stage
microphone/speaker combination. Since both the micro-
phone and stage monitor speaker exhibit their own indi-
vidual feedback tendencies, the interaction between the two
can cause pronounced feedback problems. This configura-
tion allows you to flatten or “normalize” this interaction
without actually getting to feedback levels. It should be
noted that this testing procedure favors maximum SPL
before feedback and not necessarily optimum monitor
sound quality. This configuration can also be used for main
speaker equalization to optimize system response for a
specific microphone used throughout the system, such as
for choir, orchestral or big band situations where all
program material is picked up through microphones of the
same make and model.

5. Do not attempt to plug a regular microphone directly into

the MIC INPUT. See Rane Note 104 regarding use of other
microphones with the RA 27.

MAIN SPEAKER EQUALIZATION

IMPORTANT NOTES:
1. If your sound system is stereo or multichannel, equalize

each channel individually first, then look at the combined
acoustic output of all channels, making small corrections as
necessary.

2. If you are using a powered mixer, or a mixer that has mic

level inputs only, you will need to reduce the signal level at
the pink noise output. Use a small screwdriver to adjust the
PINK NOISE LEVEL control on the rear chassis so the
Pink Noise Output suits your mixer.

3. An RA 27 can be used as a driver alignment tool (see the

AC 22/23/B Owners Manual) as well as a room-flattening
equalizer. Drivers are aligned when maximum level is
shown at the crossover frequency on the RA 27 display. It
is important to align drivers either physically or electroni-
cally 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 RA 27 mic should be in line with the
on-axis phase response of the speaker stack, perpendicular
to the drivers.

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