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VP-8IP / Sep 2013
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In the Hard mode, limiting action does not occur until the threshold within a particular
band is reached. This setting is more open sounding because no limiting activity occurs
until the threshold is achieved and once limiting does begin, the compression ratio is
very high.
In the Soft mode, limiting starts to occur at a level that is 3dB below the user-set
limiter threshold and the transfer function is relatively soft. That is, the audio waveform
is not abruptly limited, but instead is allowed to gradually increase over a 3dB window
until the ultimate limit threshold is reached, whereupon no further amplitude increase
is allowed.
Because of this behavior, the sound of the Soft function is more obvious than the
Hard setting, even though the latter is actually more aggressive in controlling levels. In
this mode, and until the ultimate limit threshold is reached, the limiters operate more
like variable ratio multiband compressors than multiband limiters.
Bass Tools
Vorsis Bass Tools allows extremely low program frequen
-
cies to be processed without causing dynamic gain changes
and without generating undesirable intermodulation artifacts
in higher frequency signals. Its primary purpose is to allow
the thumps of kick drums and other percussion instruments to
sound natural in their “percussiveness” without pumping or
other undesired artifacts. The algorithm operates in left/right
mode treating both channels identically.
Our laboratory research on codec behavior rather surpris-
ingly revealed that it is perfectly acceptable to process very low frequency material using
the Bass Tools algorithm provided that the harmonics generated during the process are
well controlled spectrally. Since our bass algorithm does not allow significant harmonic
levels above the third or fifth (somewhat dependent the Bass Tools
Style setting) there
is no audible downside to using it with coded audio. Furthermore, the ability to utilize
the Bass Tools on both the FM and HD sides of the processor allows the sound to be
more evenly matched as receiver-based digital to analog crossfades are encountered.
Comparison of Hard and Soft Limiter Modes
