Fundamentals of Audio Processors
An audio processor, also known as a digital processor, handles digital signal processing. Its internal structure typically consists of input and output sections. Key audio processing functions include: Input section: Input Gain control, Input EQ (multi-band parametric), Input Delay, Input Polarity (phase) reversal. Output section: Input signal routing selection (ROUTE), High-Pass Filter (HPF), Low-Pass Filter (LPF), Output EQ, Polarity, Gain, Delay, Limiter threshold (LIMIT).
Features
Digital Processor Input Functions:
Input Gain: Controls processor input level. Range typically ±12dB.
Input EQ: Usually 4-8 bands of fully parametric EQ. Adjustable parameters: Frequency, Bandwidth/Q, Gain.
Input Delay: Delays the input signal upon entry. Used for overall system delay alignment, e.g., when processor controls delay speakers.
Input Polarity: Reverses signal polarity (+/-) for entire processor, saving cable rewiring.
Digital Processor Output Functions:
Signal Input Routing (ROUTE): Selects input source for this output channel (e.g., Input A, Input B, Mix A+B, Mono Mix).
High-Pass Filter (HPF): Sets lower frequency limit. Used for speaker high-pass (e.g., crossover point). Parameters: Frequency, Filter Type (commonly Linkwitz-Riley, Bessel, Butterworth—choose L-R if unsure), Filter Slope (6, 12, 18, 24, 48 dB/oct—steeper slope = sharper cutoff).
Low-Pass Filter (LPF): Sets upper frequency limit. Used for speaker low-pass (e.g., subwoofer crossover). Parameters same as HPF.
HPF + LPF = Bandpass Filter. E.g., for a 3-way speaker crossed at 500Hz/3000Hz: LF LPF=500Hz, MF HPF=500Hz & LPF=3000Hz, HF HPF=3000Hz. Type: L-R, Slope: 24dB/oct—usually correct. Some processors combine filter type and slope.
Output EQ: Similar to input EQ, usually parametric only (no graphic).
Output Polarity: Reverses output signal polarity. Some processors have Phase angle adjustment (advanced).
Output Limiter: Key parameters: Threshold (Start Level), Attack Time, Release Time. Set threshold based on amp/speaker specs—prevent clipping (amp red light). Attack/Release: Slow attack/fast release for bass; Fast attack/slow release for highs; Medium for mids.
Features
Digital Processor Input Functions:
Input Gain: Controls processor input level. Range typically ±12dB.
Input EQ: Usually 4-8 bands of fully parametric EQ. Adjustable parameters: Frequency, Bandwidth/Q, Gain.
Input Delay: Delays the input signal upon entry. Used for overall system delay alignment, e.g., when processor controls delay speakers.
Input Polarity: Reverses signal polarity (+/-) for entire processor, saving cable rewiring.
Digital Processor Output Functions:
Signal Input Routing (ROUTE): Selects input source for this output channel (e.g., Input A, Input B, Mix A+B, Mono Mix).
High-Pass Filter (HPF): Sets lower frequency limit. Used for speaker high-pass (e.g., crossover point). Parameters: Frequency, Filter Type (commonly Linkwitz-Riley, Bessel, Butterworth—choose L-R if unsure), Filter Slope (6, 12, 18, 24, 48 dB/oct—steeper slope = sharper cutoff).
Low-Pass Filter (LPF): Sets upper frequency limit. Used for speaker low-pass (e.g., subwoofer crossover). Parameters same as HPF.
HPF + LPF = Bandpass Filter. E.g., for a 3-way speaker crossed at 500Hz/3000Hz: LF LPF=500Hz, MF HPF=500Hz & LPF=3000Hz, HF HPF=3000Hz. Type: L-R, Slope: 24dB/oct—usually correct. Some processors combine filter type and slope.
Output EQ: Similar to input EQ, usually parametric only (no graphic).
Output Polarity: Reverses output signal polarity. Some processors have Phase angle adjustment (advanced).
Output Limiter: Key parameters: Threshold (Start Level), Attack Time, Release Time. Set threshold based on amp/speaker specs—prevent clipping (amp red light). Attack/Release: Slow attack/fast release for bass; Fast attack/slow release for highs; Medium for mids.