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Operation Manual
I-Tech HD Series Power Amplifi ers
page 32
4.8.10 Crossover Filters
The Crossover section lets you use infi nite impulse response (IIR) or
fi nite impulse response (FIR) fi lters for the crossover.
FIR advantages: FIR has a longer processing latency but has less
phase artifacts compared to IIR. FIR allows for brickwall, 48dB/oct and
24dB/octave fi lters.
IIR advantages: FIR has one processing block per channel; IIR has one
or more. For example, you can place an FIR at only one end of a channel,
but you can place an IIR at either end.
The amplifi er contains two FIR blocks which can be used in various
confi gurations:
• 2x2 mode: One FIR fi lter per channel can be used.
• Bridge mono mode: Both FIR fi lters can be used.
• 1x2 mode: Two modes are available – Duplicate or Unique. In Duplicate
mode the same settings are used on both channels, allowing two FIR
fi lters per bandpass. In Unique mode the FIR fi lters are limited to one per
bandpass. However, if the High Pass of Channel 1 and Low Pass for
Channel 2 are set to identical slopes and frequencies, you can use FIR on
all the bandpasses. The logic for this operation is built into the software
controls. In addition, the Processing (FIR) latency sets the minimum
frequency that can be set for an FIR.
A polarity inverter button lets you change the polarity of each channel
independently.
4 Advanced Operation
Each audio channel has three separate places where fi lters can be placed in the
system: input EQ (16 fi lters), Crossover, and Output EQ. Up to 24 fi lters per
channel are available, plus crossover fi lters and 4 fi lters for the signal
generator. Each fi lter has up to +/-24dB of gain. The following fi lters are
available:
• Lowpass: Bessel 2-4, Butterworth1-4, and Linkwitz-Riley 8
• Highpass: Bessel 2-4, Butterworth1-4, and Linkwitz-Riley 8
• Lowshelf: Low-frequency shelving EQ
• Highshelf: High-frequency shelving EQ
• Lowpass EQ: Variable bandwidth, can be expressed as Q (0.100 to 35) or
Octaves (0.041 to 6.672)
• Highpass EQ: Variable Q from 0.1 to 25
• Parametric EQ: Variable Q form 0.1 to 35