OPERATING INSTRUCTIONS
Before attempting any equalization of audio with the MQ
15/MQ 30, it is important to optimize the
IN
and
OUT
GAIN
control settings. Improper gain distribution is a
common cause of headroom loss and increased noise in
audio systems.
The MQ 15/MQ 30 provides you with an overall
BY-
PASS
switch & indicator as well as an
OL
(overload) LED
as useful tools for optimizing this gain set-up. The
BYPASS
switch is useful for making quick A-B comparisons, i.e.,
comparing equalized
(BYPASS
out, LED off) versus
unequalized
(BYPASS
in, LED on) sound. To do this freely,
without danger of system damage, requires you set the level
through the MQ 15/MQ 30 to approximately unity. Failure to
do so can produce alarming results.
The input and output gain ranges of the MQ 15/MQ 30
go from -12dB to +12dB. The MQ 15/MQ 30 is always unity
gain in bypass, so if you add or reduce gain (beyond EQ
make-up gain) the level differences between
BYPASS
in/out
can be startling. Therefore you want to set the
GAIN
controls for equal in/out loudness levels.
To get started, make the following initial set-up adjust-
ments:
1.
BYPASS
switch depressed (equals bypassed condition
= red LED on).
2. Both
GAIN
controls positioned at the top of the panel,
i.e., IN @ +12 and
OUT @ -12.
3. All slide controls center-detent positions (0dB boost/
cut).
4. Apply a signal to the system.
5. Check that the OL indicator is not on. If the OL LED
is on, move both
GAIN
controls down just enough for it to
go out. The MQ 15/MQ 30 stays unity gain from input to
output because you kept both controls at equal settings, thus
ensuring the input is attenuated enough to keep it out of
overload and the output gain is making up for it. For opti-
mum noise performance always take as much gain as
possible through the INPUT stages, i.e., position the
IN
GAIN
slider as close to +12dB (the
OUT GAIN
slider
toward -12dB — keep them together) as possible.
6. Release the
BYPASS
switch and you are ready to start
equalizing the system.
Since acoustic compensation and tone contouring are two
of the most common uses for equalization, here are a few
words on each:
ACOUSTIC COMPENSATION.
Acoustic compensa-
tion is controlled nicely with a device such as the MQ 15/
MQ 30. The best way to find out what room acoustics are
doing to your sound is to use either a real time analyzer or
any of the many computerized measurement systems such as
time delay spectrometry or other similar devices. This sort of
test equipment lets you analyze the response of the combina-
tion of room and sound system and is the only accurate
means available for setting up the MQ 15/MQ 30 properly. If
It is a very good idea to always start the equalization
process with the filter
RANGE
switch in the
±6dB
posi-
tion. It should stay there unless you absolutely cannot
achieve your goal any other way. Then and only then should
you go for the
±12dB
position.
Use the
BYPASS
switch to compare equalized with
unequalized sound. Compare the two and set the equalizer as
best you can using controlled noise sources, sweep signals,
or source material that you are VERY familiar with. Try to
avoid adding too much low end. This is an area where
equalizers are frequently abused, causing lots of unnecessary
stress on amplifiers and speakers. This is particularly
important when using any sort of vented enclosure low
frequency drivers. Too much level applied to a woofer below
the cutoff frequency of its enclosure causes very large
speaker excursions and very short life.
TONE CONTOURING
with the MQ 15/MQ 30 is
accomplished mainly by ear. This you know how to do. Be
careful, though, not to introduce too much boost to the upper
bass area (and the sub-bass area as in the last paragraph). Be
aware that the MQ 15/MQ 30 is capable of boosting signals
up to 12dB — a level at which great care should be taken to
prevent seismic disturbances.
you are unable to utilize science in this way, your ears will
have to be the judge.
IMPORTANT NOTE
Please refer to Rane Note 110 (supplied with your
unit and available on request at no charge if you lose it)
for further information on system grounding.
3. Units with outboard power supplies do NOT
ground the chassis through the line cord. Make sure that
these units are grounded either to another chassis which
is earth grounded, or directly to the grounding screw on
an AC outlet cover by means of a wire connected to a
screw on the chassis with a star washer to guarantee
proper contact.
1. Try combinations of lifting grounds on units that
are supplied with ground lift switches or links.
2. If your equipment is in a rack, verify that all
chassis are tied to a good earth ground, either through
the line cord grounding pin or the rack screws to another
grounded chassis.
Rane commercial equalizers are supplied with a rear
mounted ground-lift switch. The unit is shipped with this
switch in the “grounded” position, tying circuit ground
to chassis ground. If after hooking up your system it
exhibits excessive hum or buzzing, there is an incompat-
ibility in the grounding configuration between units
somewhere. Your mission, should you accept it, is to
discover how your particular system wants to be
grounded. Here are some things to try:
CHASSIS GROUNDING
Rane Corporation 10802 47th Avenue West, Mukilteo WA 98275-5098 TEL (425) 355-6000 FAX (425) 347-7757
All features & specifications subject to change without notice. 520-327 1093
