Ashly 3.24CL-d Instrukcja obsługi - Strona 7

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Operating Manual - PROTEA SYSTEM II 3.24CL Crossover / System Processor

Parametric EQ (PEQ) uses peak fil-

ters with the ability to control boost or cut,

frequency center, and bandwidth. Think of

one band of parametric EQ as a single graphic

equalizer fader except that the frequency is vari-

able, not fixed, and that the bandwidth, or how

"wide" the filter affects the frequency spec-

trum at the center frequency, is completely

variable. The smaller the bandwidth, the less

the audio signal on either side of the fre-

quency center is boost or cut, whereas a larger

"wider" bandwidth produces an audible

change to the overall tone of a signal. Para-

metric filters are best used to hunt down and

eliminate problem feedback frequencies, add

or remove a characteristic "hot spot" from mi-

crophones, or clean up room resonance situations. It is well worth the time getting proficient with parametric EQ filters, as

they offer the best solution to many EQ problems.

Protea 3.24CL 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 three inputs and six 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.

4.6c Delay

The 3.24CL-d is the same as

the 3.34CL in every respect except for

the delay structure. On the 3.24CL-d,

the input delay is adjustable up to

85ms, and the output delay adjustable

up to 256ms.

In large installations or outdoor venues there are often many speaker clusters in various locations to get the best

coverage possible. Since sound travels relatively slow through air (1130 ft/s at 20°C), 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.

Within the Protea 3.24CL, up to 682 milliseconds of time delay are available on each input channel, allowing secondary

loudspeaker clusters to be time aligned with the primary speakers up to 771 feet (235m) away from the main stage area.

+20dB

+10dB

0dB

-10dB

-20dB

-30dB

20Hz

200Hz

3.24CL Parametric Filters

Narrow (Low) Bandwidth

Wide (High) Bandwidth

2KHz

20KHz