Ashly DPX-200 Betriebshandbuch - Seite 8

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1. Dimensions and Schematics

Operating Manual - DPX-200 Parametric Equalizer - Compressor/Limiter

8. TYPICAL APPLICATIONS

By itself, a parametric equalizer is useful for gen-

eral tone control, feedback control, room resonance cor-

rection, individual microphone voicing, and many other

applications. The compressor/limiter provides many so-

lutions where dynamic signal level processing is required.

The combination of a parametric EQ and a compressor/

limiter allows for additional applications, such as a full

range speaker processor, 70 volt distributed system pro-

cessor, mixing console channel insert, and frequency sen-

sitive limiting, just to name a few. In most cases, the

DPX-200 should be the last device before the power amp

or crossover, or right before a recording device or trans-

mitter.

8.1 Parametric Equalizer Applications

General Tone Control

Like a graphic EQ, the parametric equalizer is a

very useful device for general tone shaping because the

filter's center frequency, bandwidth and level are all con-

tinuously variable. To use the power of the equalizer ef-

fectively, you need to translate your idea of the tone you

want to produce into a range of numerical frequencies.

This is simple after a little practice. Here are a few refer-

ences which are useful for starting points:

- Very low bass (the "wind" in a kick drum, almost felt

as much as heard -40Hz-80Hz.

- The low register of a male voice - 200Hz

- The low register of a female voice - 350Hz

- Lower midrange ("warmth" frequencies) - 400Hz-

1KHz

- Upper midrange ("harshness", snare drum "bite", "hot"

sound) -2.5KHz-4KHz.

- Sibilance ("sss" sounds, cymbal "sizzle") - 8KHz-

15KHz.

Try using these starting points as a guide when

you want more or less of these types of sounds. Adjust

by ear from there. It is always a good idea to remember

that a little equalization usually works out much better

than a lot, and that there are many audio problems which

cannot be solved with equalization alone.

Feedback Control

The parametric equalizer is a powerful tools when

applied to eliminating feedback problems. On a tradi-

tional graphic equalizer, the fixed filter center frequen-

cies are insufficient when the frequency of feedback oc-

curs between two slide faders, or is extremely narrow.

The continuously variable center frequency and bandwidth

of a parametric equalizer allows very sharp notching of

feedback frequencies.

The following procedure outlines how to use a

parametric equalizer to suppress feedback frequencies:

1. Start with all the EQ switches out except the

master EQ switch in and the gain at 0.

2. With the entire PA hooked up and turned on,

slowly increase the sound level at the mixer until

feedback is heard, then lower the level by about

3 dB so that feedback does not continue.

3. Start with one of the two parametric filters by

setting the level at 0, bandwidth set fairly sharp

(about .3 oct.), and adjust the frequency control

to where you estimate the predominate feedback

frequency to occur.

4. Push in the filter's EQ switch and increase its

level control by about +6 dB. Now "sweep" the

frequency around where you have estimated the

feedback frequency until feedback occurs. Once

you have induced the feedback by boosting its

frequency, quickly turn down the filter's level

control to about -6 dB to suppress or "notch out"

the feedback frequency.

5. Again slowly increase the master level at the

mixer until feedback is heard. If a new feedback

frequency is heard, then repeat step 3 with the

other parametric filter to find and suppress the

new frequency. If the original feedback frequency

is still heard, then adjust the first filter's level

even lower. The bandwidth control may be ad-

justed full clockwise to produce a very sharp

notch so that a severe feedback frequency can be

attenuated by as much as 15 dB without degrad-

ing the frequency response with noticeable

notches. Note: Very sharp bandwidth lowers the

maximum equalizer input level because of the

high filter gain necessary to obtain such a nar-

row bandwidth. Only use bandwidth control full

CW (.05 Octave) in severe cases.

Console Channel Equalization

Many mixing consoles provide only simple equal-

ization for individual channels. If your console has chan-

nel inserts, you can patch your parametric equalizer into