Section Six - Troubleshooting Tips - SABINE FBX1200 Operating Manual

5.3.3. Setup Mode
NOTE: Setup mode is for pre-performance audio setup only, and will cause distortion in your audio program if left on during
performance. You must follow the setup procedure outlined in the previous section, and do not play program during Setup
mode. Otherwise the FBX will clip and filters may be set improperly. (Clip level is set to the lowest level so the feedback clips
quickly; therefore, your program will also be clipped in setup mode. Be sure a dynamic filter is set, and if one isn't, press the
READY button before your program begins.) You'll know the FBX1200 / FBX2400 is in setup mode when the SETUP button
is lit. NOTE: You can manually override Setup mode if necessary.
5.3.4. Mobile vs. Stationary Microphones
One significant advantage offered by the Sabine family of FBX Feedback Exterminator products is their ability to adapt to changing
acoustical relationships involving sound system components in various applications. One major source of potential feedback
problems arises in situations with wireless microphones, when the user of the wireless mic is moving around the performance
area. As a microphone moves in a sound space, with varying degrees of proximity to the speakers and varying acoustic
responses, feedback frequencies may shift. In such a situation, feedback-free mobility may be more important a concern than
maximum system gain.
For this reason we recommend setting FBX filters for mobile microphones by moving to the various possible microphone
locations and setting filters for those locations. As the Setup instructions show, raise the system gain and set the FBX filters in
each predictable location.
In some situations, increasing the number of dynamic filters (versus fixed FBX filters) may allow a second layer of defense
against new feedback from new locations. This technique is recommended if you cannot predict where the performer may
roam. But fixed FBX filters placed in the setup procedure are still your best bet because the feedback filters are already set.
SECTION SIX — TROUBLESHOOTING TIPS
Q. Can I place the FBX in the mixer's EQ loop?
A. Yes.
Q. Can I place the unit in the mixer effects loop?
A. Avoid this configuration. You can configure the system this
way only if each effects send of each mixer channel is set
so that all of the signal is routed completely through the
effects loop. You cannot mix dry signal with effects signal
and still control feedback.
Q. The signal input LEDs do not light. The unit will not catch
feedback. Why?
A. The unit is not in the signal path. Check the connections.
Be sure that the program is interrupted when the input is
disconnected from the back of the unit.
Q. Can I mix balanced and unbalanced inputs and outputs?
A. Yes. An unbalanced input and balanced output is compat-
ible. However, a balanced input and unbalanced output will
result in a 6 dB loss of dynamic range. Refer to section
5.3.5. for more details.
Q. Why does one of the FILTER ACTIVITY LEDs blink?
A. The last filter to be automatically updated blinks. During
normal operation, the blinking will move from filter to filter
as they are reset. This gives the user a visual confirmation
that the unit is responding to new feedback and is function-
ing properly.
Q. Sometimes during the initial setup, the first filter LED will
blink before any feedback has been introduced into the
system. Why?
A. The FBX will set a filter if the system has a hum. Check for
bad grounds. Try resetting the filters and/or the Ground
switch on the rear panel.
Q. Why do I have a loss of 6 dBs at the outputs?
A. Your outputs are connected to an unbalanced connector,
causing a loss of 6 dB through the box. You can put your
FBX in unbalanced mode, giving the box a boost of 6 dB at
the outputs. To change between balanced and unbalanced
mode, hold down the SETUP and RESET DYNAMICS buttons
at the same time. Refer to section 5.2. for more details.
Q. Why does my system sound thin and muffled?
A. Place the FBX in BYPASS MODE. If the system still sounds
thin, your problem is probably improper use of a graphic
EQ. If the problem is really the FBX, re-initialize the system
and make sure the READY button LED is on steadily.
Q. Why does my program sound clipped and distorted?
A. Make sure you are not in Setup mode. Setup mode turns
off automatically after the first dynamic filter is set, or you
can turn it off manually by pressing the READY button. See
Section 4.3.3. for information on Setup mode.
Q. Can I patch two FBX channels together for twice the
filters?
A. Yes; connect the output of one FBX channel to the input of
the other channel. Place the FBX between the output of
the mixer and the input of a power amp, and set up the
channels sequentially. When combining channel A with
channel B on an FBX2400, bypass channel B while setting
up channel A, then lock channel A's fixed filters (all channel
A's filters should be fixed) by pressing channel A's READY
button on the front panel after setup. The blue READY LED
should remain lit.
Q. Why doesn't the FBX1200 & FBX2400 Series filter feed-
back immediately?
A. Four possible reasons:
1. Lower frequencies may take longer than higher ones.
2. Check input level of signal at the unit and set gain so
the signal level LED's on the unit light up.
3. It may be patched in an "effects loop", not directly in the
signal path. This WILL NOT WORK.
4. You may have used all 12 filters. Dynamic filters will
continue to operate by notching feedback frequencies
as they occur, but ultimately, gain will exceed filter
capacity.
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