Behringer DSP1100P Manual do Utilizador descarregar pdf (Página 21)

0 dB

-2 dB

-4 dB

-6 dB

-8 dB

-10 dB

-12 dB

1 kHz

5 kHz200 Hz

Bandwidth = 600 Hz

Filter attenuated by 8 dB at 1kHz

Center frequency

= 1 kHz

-3 dB

Fig. 4.2: Typical equalizer filter curve

The filter bandwidth can also be expressed in octaves (as on the FEEDBACK DESTROYER PRO). The

following table shows a list of decimal Q values vs. octaves:

Octave Quality factor (Q)

1/6 8.65

1/4 5.76

1/3 4.32

1/2 2.87

3/4 1.90

11.41

3/2 0.92

20.67

30.40

Tab. 4.1: Octaves vs. Q factors

Now the following relationship becomes clear: the higher the Q factor, the narrower the frequency band that can

be cut or boosted. On the BEHRINGER FEEDBACK DESTROYER PRO you can adjust the relative bandwidth

conveniently with the infinitely variable jog wheel. The filter bandwidth can be tuned from 2 octaves (120/60

octaves) down to 1/60 octave (for fine adjustments).

4.1 Feedback

Almost every concert goer may have experienced the howling and squealing of an improperly set sound

reinforcement system. Feedback is one of the main problems encountered during live events. A feedback loop

is produced when a microphone signal is reproduced by an amplifier system, to be picked up again (with the

same phase) by the microphone. Thus, feedback is built up at all frequencies where the distance between

microphone and speaker corresponds to a multiple of the signals wavelength.

4. TECHNICAL BACKGROUND

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