Ashly Protea DSP480 Panduan Pengoperasian - Halaman 7

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Operating Manual - PROTEA™ DSP480 and DSP360 System Processors
whereas a larger "wider" bandwidth produces an
audible change to the overall tone of a signal.
Parametric filters are best used to hunt down
and eliminate problem feedback frequencies,
add or remove a characteristic "hot spot" from
microphones, or clean up room resonance situa-
tions. It is well worth the time getting proficient
with parametric EQ filters, as they offer the best
solution to many EQ problems.
Protea parametric filters have a boost/
cut range of +15dB to -30dB. There is more cut
than boost because one of the more common
uses for parametric filters is to dramatically
cut, or "notch out", very narrow frequencies
(low bandwidth) in order to eliminate system
feedback problems.
Every instance of a parametric EQ filter has a center frequency selected. The factory default is 1kHz, but each filter's
center frequency is adjustable from 19.7Hz to 21.9kHz in 1/24 octave steps. Carefully sweeping a narrow bandwidth filter through
a problem feedback area, with just a slight boost, is a quick way to find the exact frequency causing trouble. Once the offensive
frequency has been found, cut the filters level, and then the bandwidth is adjusted as narrow as possible while still eliminating
the feedback problem. Bandwidth is adjustable from about 1/64 octave to four octaves, and the lower the bandwidth, the less
audible the filter action will be. Finding the problem frequency is relatively easy, but finding the best combination of cut and
bandwidth takes a little practice. Again, it is well worth the time becoming comfortable with the notching procedure, so that
problems can be quickly addressed with a sufficient but minimal amount of correction.
The EQ functions on all four inputs and eight outputs are switched in or out on an individual channel basis. In other
words, each input or output has one "switch" for all of its EQ filters. If certain filters are not going to be used within a channel,
simply leave the gain for that filter at 0.0dB, and the filter will have no effect.
For an excellent interactive display of the way parametric and shelving filters work, experiment with the DSP480 or
DSP360 EQ section of Protea NE Software. The software works whether a unit is connected or not, so it is an invaluable teach-
ing tool as well as an audio setup tool for Protea products. The program is available on the Ashly web site.
4 .6c Delay
In large installations or outdoor
venues there are often many speaker
clusters in various locations to get the
best coverage possible. Since sound trav-
els relatively slow through air (1130 ft/s
at 20ºC), multiple loudspeaker locations
can create a situation where the original
audio signal, simultaneously leaving all loudspeakers, arrives at a single point in the venue at several different times. Needless
to say this causes problems, and what may be crystal clear sound directly in front of any one loudspeaker can be unintelligible
in the farther reaches of the venue with direct line-of-sound to multiple loudspeakers. The solution is to delay the audio signal
to the loudspeakers located beyond the main stage area, so that sound comes out of the distant loudspeakers at the exact time
that sound from the main stage loudspeakers arrives. Up to 682 milliseconds of time delay are available, allowing secondary
loudspeaker clusters to be time aligned with the primary speakers up to 771 feet (235m) away from the main stage area.
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