SABINE Graphi-Q2 3122-S User Manual
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An FBX FILTER is essentially an automatically placed, narrowly attenuated parametric filter, with
the center point of its narrow cut tuned to a precise frequency that feeds back when a sound system
amplifies one or more microphones to a sufficient volume. The Graphi-Q2 will automatically place
up to 12 FBX filters in the signal path, corresponding to 12 distinct frequencies of feedback.
•
A FIXED FBX FILTER will not change the frequency of the filter notch. Once it sets itself, it remains
at the same frequency. However, unless it is LOCKED, a FIXED FILTER may move its notch deeper
without changing frequency. Fixed filters are typically set by turning up system gain to the point of
feedback prior to sound check or performance, and will represent the “first layer” of feedback
protection.
•
A DYNAMIC FBX FILTER acts like a Fixed filter, until all available FBX filters (Fixed or Dynamic)
are in use and a new frequency begins to feedback. When this happens, whichever Dynamic filter
was set earliest in the performance will drop its original frequency and move to the new one. Dynamic
filters are especially useful with mobile or wireless microphones (where feedback frequencies may
change due to microphone repositioning) and represent the “second layer” of feedback protection.
Note that both Fixed and Dynamic filters can be set while music is playing (except when in Setup
Mode). One of the distinguishing properties of the Sabine FBX algorithm is its ability to distinguish
music (or speech, or other sounds) from feedback.
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A LOCKED FBX FILTER is a Fixed filter locked in place; i.e., it cannot get any deeper or change
its frequency. Locking Fixed filters ensures your first layer of feedback protection is always in place.
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FILTER WIDTH generally refers to the width (measured in octaves, or fractions thereof)
of a filter, including graphic EQ filters, parametric filters, and FBX filters. More specifically, width
is defined by determining the outer frequencies (surrounding the filter center point) that are altered
± 3 dB when the filter is imposed. This is shown in the diagram below:
In this example, the filter width is defined as approximately one-half octave, corresponding to the
band of frequencies attenuated 3 dB or more when the filter is pulled down. In this example, the width
is the same whether the
filter depth is -9 dB or -19
dB.
•
CONSTANT Q filters are
filters whose widths remain
constant regardless of the
amount of boost or attenu-
ation imposed by the fil-
ters. In other words, in the
above example, a Con-
stant Q filter that was one
half-octave wide would re-
main a half-octave wide
regardless of the EQ slider
position. Some EQ units
on the market are Con-
stant Q; others are Pro-
portional Q, meaning the
filter gets wider as it gets
deeper. All Sabine products use Constant Q filters, to prevent affecting any more sound than
necessary.
•
FBX Setup Mode refers to Sabine’s unique, exceptionally fast method of placing FBX filters during
sound system setup. Setup Mode is less “fussy” about analyzing the sound it hears and is more
likely to regard audio signals over a minimum threshold as feedback. It’s also designed to allow
feedback to occur at lower input levels, and, finally, it imposes a strong limiter on the feedback output
as it occurs. The net result of all this black magic is that you are able to ring out feedback more
quickly, and at a much quieter level! You’ll know Setup Mode is engaged when the Setup LED (at
the right of the front panel) is illuminated.
NOTE: MAKE SURE Setup Mode IS OFF WHEN YOU USE THE Graphi-Q2 OR YOUR AUDIO SIGNAL
QUALITY MAY SUFFER! (See Section 6.4.2.3 Setup Mode Cautions).
S
ECTION
S
IX
: U
SING
G
RAPHI
-Q2 C
ONTROLS
True Constant Q filters:
widths remain constant
as the filters get deeper.
Standard on all Sabine
products.
IMPORTANT
FBX Setup Mode
OFF During
Performance