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IQ–P.I.P.–DSP Programmable Input Processor with DSP for IQ Systems
Reference Manual
level would indicate a sudden decrease in the load
impedance—such as a shorted speaker cable or
shorted loudspeaker. There are two parameters which
control this feature:
ODEP Short Detect:
Turns this function on/off.
ODEP Short Level:
Sets the
ODEP level above
which a short is presumed to have occurred in the
load resulting in a warning message being
displayed. The range is from 1 to 100%.
4.18 Fault Warning
Fault conditions can be monitored by the
IQ System
and a warning message displayed on the host
computer’s screen if they occur. If desired, the AUX port
can also be turned on during a “fault” condition. An
amplifier “fault” condition occurs when a channel fails.
The symptoms are a normal input signal, an
IOC condi-
tion that is “locked” on, a high voltage supply (VCC)
that reports a normal condition and no signal at the
output of the amplifier.
PIP2-compatible amplifiers
monitor a “fault” signal from the amplifier while stan-
dard
P.I.P.-compatible amplifiers deduce a “fault” con-
dition from the aforementioned symptoms. There are
two parameters which control this feature:
Fault:
Turns this function on/off.
Input Drive Level:
Sets the threshold below which
a fault condition is presumed to exist in a standard
P.I.P. amplifier. This parameter is necessary
because it may be normal for an
IOC error to
persist if the audio input signal level is high.
Monitoring the input level can help determine
whether a fault condition really exists or whether
the amplifier output is distorted simply because of
an excessive input level. The range is from +16
dBu to –40 dBu.
4.19 Signal Delay
A signal delay is available for each channel. Each one
is controlled by the
IQ System and has one parameter:
Delay:
Sets the amount of signal delay. The range is
1.25 milliseconds to 0.175 seconds in 22.7
microsecond steps. (The minimum delay of 1.25
milliseconds is inherent in the DSP system design.)
Note: The signal delays are not disabled by the ASA
control.
4.20 Programmable Filters
Each channel can have as many as eight different
cascaded filters (the actual number depends on the
mix of filters chosen and the total number of required
filter cells). There are seven different filter types from
which to choose—all controlled by the
IQ System:
Low-pass crossover filter (1st–4th order)
High-pass crossover filter (1st–4th order)
Parametric equalization filter (2nd order only)
Low-pass equalization filter (2nd order only)
High-pass equalization filter (2nd order only)
Low-pass shelving equalization (1st order only)
High-pass shelving equalization (1st order only)
All filters have IIR based topologies to insure a proper
magnitude/phase relationship for use in professional
audio applications such as equalizer or crossover
(dividing) networks. Each channel has a total of eight
“biquad” filter cells.
Note: “Biquad” refers to the double
quadratic equations which mathematically describe
each filter implemented in the digital signal processor.
The 1st and 2nd-order filters each require one biquad
filter cell. The 3rd and 4th-order filters each require two
biquad filter cells. This means that a channel can have
no more than four filters if they are all 3rd or 4th-order
filters. Remember that only eight filter cells are
available—this limits the total number of filters that a
channel can have. An error message will be reported
by the IQ software if this capacity is exceeded.
A description and list of the parameters of each filter
type are presented next:
Low-Pass Crossover Filter
Description: This filter rolls off high frequencies
at a rate determined by the shape parameter.
The filter is commonly used to feed the low
frequency portion of an audio signal to woofers
or subwoofers. It can be combined with a high-
pass crossover filter to create a band-pass
crossover filter for driving mid-range drivers.
Passband gain:
Fixed at unity.
Frequency:
Sets the –3 dB corner frequency of
the filter. The range is 20 Hz to 20 kHz.
Shape:
Sets the response shape of the filter.
Available response shapes are: 1st-order
Butterworth, 2nd-order Butterworth, 3rd-order
Butterworth, 4th-order Butterworth, 2nd-order
Bessel, 3rd-order Bessel, 4th-order Bessel and
4th-order Linkwitz-Riley.
High-Pass Crossover Filter
Description: This filter rolls off low frequencies at
a rate determined by the shape parameter. The