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B1-SWM-Op-Guide-v4.pmd 030108-hto
SECTION SIX : FBX FEEDBACK EXTERMINATOR
6.1 Introduction to FBX
WHY FBX? Feedback is certainly the most embarrassing, most pervasive challenge to the audio
industry. The potential appearance of sudden, loud, out-of-control feedback is every sound engineer’s
and musician’s nightmare. It disturbs the performer, the audience, and the technician; and can damage
equipment and just generally ruin your day.
A typical wireless microphone adds a new level of unpredictability to feedback potential. Feedback
involves a relationship between a speaker and a microphone, and the physical distance between the two
is the principal determinant of feedback. A mic that can move anywhere results in an ever changing
potential for feedback. A step in the wrong direction may change a clear, loud sound to a piercing shriek
in less than a second. The potential for feedback with a wireless system is increased further if lavalier
microphones are used. Lavalier microphones are placed farther from the mouth than handheld or head
set microphones, and often require more gain. Lavalier microphones are also frequently omnidirectional,
meaning they pick up sound equally from all directions, increasing the chance of feedback due to
increased sensitivity to the sound emanating from the speakers.
The Sabine True Mobility
TM
solves this problem
by attenuating very narrow bands of feedback-
prone frequencies. The process is automatic,
simple to use, adaptable to changing acousti-
cal conditions and relationships, powerful in its
application, and has minimal consequences to
the audio fidelity of the signal. We call this
automatic filter an FBX Feedback Extermina-
tor
®
filter, or FBX filter for short.
Before the invention of FBX, the most common
device for controlling feedback was the 31-band
graphic EQ. However, FBX has three distinct
advantages. The most obvious is that FBX func-
tions automatically, even during the program.
Another is that FBX micro-filters are precisely
placed anywhere feedback occurs, while EQ
filters are limited to 31 fixed centerpoints. The
difference: FBX filters do not have to be as deep,
so there is more system gain. But the most
important advantage is that FBX micro-filters are
ten times narrower than 31-band EQ filters.
Using FBX micro-filters will return up to 90
percent of the power removed by EQ filters.
An EQ would need more than 10,000 sliders to
be equivalent to your FBX. With FBX technology,
your microphone will finally sound loud enough,
everyone in the audience will understand each
word, and feedback will be far less likely to make
an unwelcome and unexpected visit.
Section SIX : FBX Feedback Exterminator
Figure 6a - Graphic-EQ effect on program
If the graphic EQ really had 1/3 octave filter
widths, the frequency response curve would
vary 6 dB between sliders. This would ruin
the sound.
Graphic EQs usually use one-octave-
wide overlapping filters that provide
much smoother frequency response
curves. Notice that the overlapping fil-
ters add together to cut -16 dB when
the sliders are only pulled down -10 dB.
-10 dB cut at 500, 630,
1K, 1.25K, 1.6K &2K Hz
Содержание TRUE MOBILITY WIRELESS SYSTEM SWM3000
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