dbx DriveRack PA2 - Manual (Page 48)

44
®
• THRESHOLD [-60 dB to 0 dB]
This parameter sets the level at which the limiter will kick in and begin limiting the
signal. The limiter Threshold Meters (shown to the right) indicate when signal is below
threshold, above threshold, or in the OverEasy region. For example, if the threshold
parameter is set to -17 dB, any signal which exceeds -17 dBFS will be limited, while
any signal lower than -17 dBFS will be left alone. You will want to set the threshold
to a setting just below the clip point of the amp. For example, if your amp clips at +6
dBu, based on where you have set your amplifier attenuators, you would want to set
the limiter’s THRESHOLD to about -14 dB. Note that it is possible for short peaks to
exceed the threshold by approximately 3 dB. To be absolutely safe, you can lower the
threshold by an additional 3 dB to provide a “3 dB cushion”. This would mean, in the
previous example, that the threshold would be set to -17 dB as shown in the following
illustration.
THRESHOLD METER
Preset 1
1
EDIT
COMPRESSOR
HIGH LIMITER
MID LIMITER
LOW LIMITER
30 12 5 0
O
O
O
O
Signal Below Threshold
Preset 1
1
EDIT
COMPRESSOR
HIGH LIMITER
MID LIMITER
LOW LIMITER
30 12 5 0
O
O
O
O
Signal Above Threshold
Preset 1
1
EDIT
COMPRESSOR
HIGH LIMITER
MID LIMITER
LOW LIMITER
30 12 5 0
O
O
O
O
Signal Approaching Threshold
(OverEasy™ Turned On)
Safe Zone
+20 dBu (0 dBFS)
PA2 Output Clip Point
+6 dBu (-14 dBFS)
Amp Clip Point
3 dB
Cushion
Limiter Threshold
-17 dB (-17 dBFS)
Amp Clipping
Gain Structure & Limiter Threshold Setting Example
• OVEREASY [OFF, 1-10]
One criterion that determines how a limiter will function is called the “knee”. The knee region exists at or around the limiter’s
threshold setting and determines how gradual or abrupt the limiting will be. A limiter with hard knee characteristics won’t
limit the signal until it exceeds threshold and will provide a more abrupt and aggressively limited sound, as well as retain
more of the attack and level of the original sound. Conversely, a limiter with soft knee characteristics will begin limiting
the signal lightly before it has actually exceeded threshold and will apply more limiting as the signal level approaches
thershold, applying full limiting once the signal does exceed threshold. This can generate smoother, more musical limiting for
applications that require a smooth (“round”) sound, rather than an aggressively limited (“attacky”) sound.
The OVEREASY parameter in the PA2’s limiter module varies the knee characteristics of the limiter. When set to OFF, the
limiter will function as a hard knee limiter, making it sound more aggressive as described above. Setting this parameter to a
setting between 1-10 will cause the limiter to act as a soft knee limiter, yielding more gradual, smooth, and natural limiting.
The OVEREASY parameter’s 1-10 range is referred to as VariKnee™. Lower values provide a slightly softer knee than a
hard knee limiter. As you increase the OVEREASY setting, the knee softens, rounding out the sound. This lets you choose
the exact knee that is needed for the dynamic effect you are looking for.
Generally, a hard knee limiter will sound louder, more aggressive, and more audible when limiting – although when the
PA2 is configured for 2-way or 3-way operation, the output limiters become “band limited”, making these artifacts far less
audible. The softer the knee, the lower in level the source will sound, but the smoother and less noticeable the limiting will
be. Use proper judgement, depending upon the application and/or genre of music being reproduced through the sound
system, and experiment to find the best setting that works for your application.