Rane RA 30 - Manual (Page 7)

Manual-
Alignment Instructions
Since the RA 30 features a unique form of realtime analyzer,
we highly recommend that you read this section before perform-
ing an alignment with pink noise. If you’ve never used an ana-
lyzer before, use these instructions on your first occasion. You’ll
be delighted at how simple it really is.
WEIGHTING FILTERS
Used in SPL mode, the filter “weights” or gives more atten-
tion to certain frequency bands than others. Weighting filters are
a special type of band-limiting filters designed to compliment the
way we hear. Since the ear’s loudness vs. frequency response is
not flat, it is argued, we should not try to correlate flat frequency
vs. loudness measurements with what we hear.
A-WEIGHT: The A-curve is a wide bandpass filter centered
at 2.5 kHz, with ~20 dB attenuation at 100 Hz, and ~10 dB
attenuation at 20 kHz, therefore it tends to heavily roll-off the
low end, with a more modest effect on high frequencies. It is the
inverse of the 30-phon (or 30 dB-SPL) equal-loudness curve of
Fletcher-Munson. A-weighting is preferred for background music
and systems that will be normally operated at a low level.
C-WEIGHT: The C-curve is “flat,” but with limited band-
width, with -3 dB corners of 31.5 Hz and 8 kHz, respectively. C-
weighting is preferred for home cinema, live sound, and systems
optimized for operation at full volume.
BACKGROUND NOISE CHECK
Any background noises such as air conditioners, talking, wild
animals, traffic and the like can cause false readings on the ana-
lyzer display if the pink noise volume through the speakers is not
loud enough to drown these noises out. Before turning on the
Pink Noise, set up the RA 30 for RTA mode with the SCALE
set to the 6 dB setting. Turn the GAIN control on the RA 30
fully clockwise and press the NORMAL button: now you’re
looking at background noise. Slowly turn the GAIN control
back counter-clockwise until only the bottom row of red LEDs
are on, and no background noise is showing on the display. If
the GAIN control is turned up (clockwise) from this setting, the
background noise will falsify the readings.
PINK NOISE RUN-UP
Turn down your mixer output controls before switching on
the Pink Noise, so that you don’t detonate your speakers. Now
switch the RA 30 PINK NOISE button ON and turn up the
mixer (and EQ Level) controls slowly until you hear pink noise
through the speaker(s). Increase the Pink Noise Level until some
of the upper row yellow LEDs are on or the OL LED starts flash-
ing, whichever comes first. There is a Pink Noise Output Level
Adjustment on the rear of the RA 30 — use a 3/16" screwdriver
to vary the amount of Pink Noise to the mixer if necessary.
Proceed to adjust your equalizer with tips from the following
sections. Typically start with 6 dB SCALE and fine tune as you
work down through 3 dB and then in some instances 1 dB. If
the display is too “jumpy,” then the larger scales work better.
MICROPHONE PLACEMENT
If you are using the analyzer to measure response from a
single predetermined location or “sweet spot,” then the mic natu-
rally goes right there for testing. For larger audience areas, per-
form the pink noise test with at least two different test microphone
locations for each separate channel of EQ. Since speaker disper-
sion 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. 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. Analyze
one channel at a time.
INITIAL SYSTEM ALIGNMENT
Before using the equalizer for adjustment, use the analyzer to
align other equipment 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).
EQUALIZER SLIDER ADJUSTMENTS
Now adjust each slider up or down as necessary until the
green LED corresponding to the same frequency is lit. 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 vol-
ume or GAIN 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 is affected by both sliders. Not to worry:
simply nudge the adjacent slider until the green LED lights up
again.
FINAL EQUALIZER ADJUSTMENTS
Once the RA 30 is all “greened out”, you’re done with the
pink noise alignment test. Now the speakers are properly coupled
to the specific room and the overall system response is accurately
aligned. This alone will make a great improvement in most
systems, but don't stop at flat necessarily. Now that the RA 30 has
given you a consistent starting point, feel free to make further
slider adjustments during the performance or sound check to
enhance overall sound quality. Fatten the bass, smooth the
mids or sweeten the highs to taste. You will probably find these
adjustments will be consistently set above or below the Pink