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FM-531HD / May 2013
F M - 5 3 1 H D P R O G U I
VBMS (Vorsis Bass Management System)
The Vorsis Bass Management System allows extremely
low program frequencies to be processed without causing
dynamic gain changes and without generating undesir‑
able intermodulation artifacts. Its primary purpose is to
allow the thumps of kick drums and other percussion
instruments to sound natural in their “percussiveness.”
The algorithm operates in left/right mode treating both
channels identically.
Our laboratory research has revealed that it is perfectly acceptable to process very
low frequency material using the VBMS prior to all modern FM exciters provided that
the harmonics caused by the VBMS are well controlled spectrally. Since our algorithm
does not allow significant harmonic levels above the third or fifth harmonic (depending
on the Style setting) there is no audible downside to using the VBMS with coded audio.
Furthermore, the ability to utilize the VBMS on
both the FM and HD sides of the pro‑
cessor allows the sound to be more evenly matched as receiver‑based digital to analog
crossfades are encountered.
Drive
This control adjusts the amount of drive to the VBMS algorithm and is adjustable
over a range of +/‑ 6dB.
Style
Two VBMS operating styles, plus Off, are available. The
Hard setting has a transfer
function occupying approximately 1dB of transition amplitude. The waveform control is
fairly abrupt and generates a fair amount of low order harmonics; however, we eliminate
everything above the fifth harmonic. The
Soft setting operates with a transfer function
occupying approximately 2dB of transition amplitude. Therefore the control is less sharp
than the hard setting, generating even fewer harmonics.
While the two settings may appear to be almost the same, because the transition am‑
plitude is 1dB greater on the soft setting there is a
significant
difference in how the two
VBMS transfer functions
sound on actual program material.
Output
The VBMS
Output
control adjusts the output of the VBMS algorithm and can be thought
of as a “low bass mix” control. Settings higher than 0.0dB add more bass sound to the
overall mix, while settings lower than 0.0dB reduce the amount of bass. Both the VBMS
Drive
and the VBMS
Output controls may be generally adjusted to taste. However, care
should be exercised in the setting of the VBMS
Output control because settings above
about +3dB may cause the amplitude of bass to reach the master clipper and added distor‑
tion may result. Like VBMS Drive, VBMS Output is adjustable over a range of +/‑ 6dB.
VBMS Frequency
The VBMS
Freq
control tunes the VBMS algorithm’s frequency of operation from
60Hz to 300Hz with the program energy that is not passing through the algorithm time
aligned for coincidence regardless of the settings.
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...
