All features & specifications subject to change without notice. 520-124 JUL95
Printed in the U.S.A. on Recycled Paper
©Rane Corporation 10802 47th Avenue West, Mukilteo WA 98275-5098 TEL(206) 355-6000 FAX(206) 347-7757
OPERATING INSTRUCTIONS
Before attempting any equalization of audio with the FME
15, 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 FME 15 provides you with an overall
BYPASS
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 FME 15 to approximately unity. Failure to do so can
produce alarming results, when A-B-ing.
The input and output gain ranges of the FME 15 go from –
12dB to +12dB. The FME 15 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
equals red LED on).
2. Both
GAIN
controls center-detent positions.
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 FME 15 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
optimum 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. If the
OL
LED is not on, then leave the
GAIN
controls in their
center-detent positions. Do not increase the gain above this
point until you do enough cutting with the EQ controls to
warrant adding make-up gain.
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 compensation
is controlled nicely with a device such as the FME 15. The
best way to find out what room acoustics are doing to your
sound is to use either a real time analyzer or computerized
measurement systems such as time delay spectrometry or
other similar devices. This sort of test equipment lets you see
the response of the combination of room and sound system
and is the only accurate means available for setting up the
FME 15 properly. If you are unable to utilize science in this
way, your ears will have to be the judge.
It is a very good idea to always start the equalization
process with the filter
RANGE
switch in the
±6dB
position. 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 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 enclo-
sure 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 FME 15 is accom-
plished 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) to prevent
your audience from calling 911. Be aware that the FME 15 is
capable of boosting signals up to 12dB —a level at which
great care should be taken to prevent seismic disturbances.
IMPORTANT NOTE
CHASSIS GROUNDING
Rane Flex Series modules 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:
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.
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.
Please refer to Rane Note 110 (supplied with your
product and available on request at no charge if you lost
your first one) for further information on system ground-
ing.