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FM-531HD / May 2013
F M - 5 3 1 H D P R O G U I
Threshold
The Threshold control determines when limiting will start in a particu‑
lar band. The range for the FM‑531HD limiter threshold control can be
adjusted over a 12dB range to offset the 31‑band Limiter Drive.
Attack
This control determines how quickly the Limiter will respond to audio
once it exceeds the limiter threshold. Recommended settings are between 30 and 10ms
Release
The Release time determines how quickly the limiter will return to 0dB once audio
has fallen below the limiter threshold. Faster release times will yield a louder sound while
slower times will yield a smoother sound at the expense of loudness.
Because of the way the 31‑band limiter works, there is a lot of leeway with attack
and release times and these controls have been set so that the end user doesn’t drive the
car “off the cliff.” Basically, only extreme settings will yield a totally undesired sound.
That being said, these controls should also not be adjusted haphazardly.
Lookahead Limiter
The output of the 31‑band Limiter can be peak controlled by a special high‑speed
feed forward limiter with a 0.5 millisecond look ahead time. The control path, and not
the audio path, is oversampled in order to achieve extremely precise peak control. Be‑
cause the goal of oversampling is better peak control through finer definition of the audio
waveform, oversampling of the audio signal itself is not only unnecessary, but wastes
DSP resources. The graphic below visually illustrates why control signal oversampling
is more effective.
Summary of Contents for FM-531 HD
Page 2: ...Technical Manual Wheatstone Corporation May 2013 FM HD Digital Audio Processor FM 531hd...
Page 122: ...page A 2 FM 531HD May 2013 A P P E N D I C E S Appendix A General Specifications A 3 Contents...
Page 128: ...page A 8 FM 531HD May 2013 A P P E N D I C E S Appendix B FM 531HD GPI Interface A 9 Contents...
