BSS Audio FDS366T OMNIDRIVE User Manual page 25

Dynamic Equalisation
Notes and Uses Frequency selective compressing
Conventional compressors affect the whole audible band of frequencies
equally. Some compressors can be configured to only start compression when
they encounter given frequencies, however, once they start compressing they
compress the whole audio band. This is quite distinct from the type of
compression available in the FDS-366T DEQ.
The DEQ can be set up so that when it encounters a given band of frequencies
it compresses only that band, this is a very different technique from simple
equalisation and is vastly more powerful for both corrective applications and
creative manipulation.
To use Dynamic EQ as a wide band compressor, use high pass (i.e low
shelving) with a low frequency or vice versa.
Use with Stereo sources
To avoid 'image shift' when stereo sources are compressed the input DEQs
have their sidechains linked when the Stereo Link parameter is set to "On" .
Control of horn distortion
Above a certain critical sound level output, horn loaded speakers often start to
produce distortion. This is due to the irregular movement of air in the horn
throat and is usually a problem over a restricted range of frequencies. The band
of frequencies affected is dependent on the dimensions of the horn.
The DEQ can be used to reduce the energy in the frequency band that
aggravates the horn, resulting in both a much-improved sound and the
possibility of higher sound levels.
To do this:
1
With some program material playing, set the EQ shape of the DEQ to
Bell with some boost.
2
Manipulate the sound system level, DEQ frequency and width
parameters to find the frequency band that is causing problems.
3
Make this band as narrow as possible using the width parameter,
ensuring that the DEQ is initially set to "Off".
4
Set the EQ to cut and increase the system sound level until there is
unacceptable distortion.
5
Adjust the threshold ("Thr") parameter until the distortion is diminished.
6
Try different ratio and filter settings to achieve the best response.
- 25 -
FDS-366T