Crown Audio IQ P.I.P.-DSP manual Fault Warning, Signal Delay, Programmable Filters

IQ–P.I.P.–DSPProgrammable Input Processor with DSP for IQ Systems

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

1.25milliseconds 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

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