OPTIMOD SURROUND PROCESSOR TECHNICAL DATA
6-1
Section 6
Technical Data
Specifications
It is impossible to characterize the listening quality of even the simplest limiter or
compressor based on specifications, because such specifications cannot adequately
describe the crucial dynamic processes that occur under program conditions. There-
fore, the only way to evaluate the sound of an audio processor meaningfully is by
subjective listening tests.
Certain specifications are presented here to assure the engineer that they are rea-
sonable, to help plan the installation, and make certain comparisons with other
processing equipment.
Performance
Frequency Response (Bypass Mode): Surround Processing: ±0.10 dB, 20 Hz–20 kHz for
44.1 kHz or higher input/output sample rates. At 32 kHz input and/or output sample rate,
the passband is reduced to approximately 14.7 kHz.
Noise: Output noise floor will depend upon how much gain the processor is set for (Limit
Drive, AGC Drive, Two-Band Drive, and/or Multiband Drive), gating level, equalization,
noise reduction, etc. The dynamic range of the A/D Converter, which has a specified
overload-to–noise ratio of 110 dB, primarily governs it. The dynamic range of the digital
signal processing is 144 dB.
Polarity (Bypass Mode; Operate Mode when processing chain is configured for linear
phase): Absolute polarity maintained. Positive-going signal on input will result in positive-
going signal on output.
Internal Processing Sample Rate: 48 kHz. We believe this provides maximum audible
transparency by minimizing numerical “noise” in the equalizers and filters while still pre-
serving a pure, transparent sound. The double-precision equalizers and crossover filters
used throughout the 8685 produce at least 6 dB lower noise and nonlinear distortion
than they would at 96 kHz.
Processing Resolution: Internal processing has 24 bit (fixed point) or higher resolution;
uses 12 Freescale (formerly Motorola) 150 MHz DSP56367 DSP chips.
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