Audiovox PEQ-200 User Manual download pdf (Page 18)

ULTRA-Q PRO PEQ2200

8. SPECIAL APPLICATIONS

8.1 Equalizing a sound reinforcement system

Before you insert an equalizer in your sound reinforcement system, you should clearly define its tasks. If you

fail to set up the EQ properly, it might deteriorate the sound image more than if you used no sound-processing

device at all.

In a sound reinforcement system equalizers are used in three major areas of application:

1. Reducing the risk of feedback, while increasing the overall volume level.

2. Improving the natural sound of music.

3. Improving the intelligibility of speech.

It is quite obvious that compromises must be made to meet these requirements. In rooms with poor acoustics

or a high level of background noise, both natural sound and acoustic power can usually not be realized

simultaneously. Priority must be given to one of these quality-improving measures.

However, it should be noted that even a perfectly natural sound is useless if the audience has difficulties

understanding what a speaker says, for example at an election campaign rally!

Before you start equalizing your system it will be useful to play back some music or speech program without

equalization. If the sound is distorted you should first try to eliminate this problem. In order to get a feel for the

room acoustics it might be helpful to sweep a sine tone generator over the entire audio range (i.e. the

frequency range from 20 Hz to 20 kHz), which is better than playing back a signal consisting of pink noise, as

it will enable you to identify weak points (room resonances, distortion, rattling noise) of both system and

location. In particular, the critical range between 2 and 4 kHz should be tested (if required, use the BEHRINGER

ULTRA-Q PRO as a band-pass filter to limit the frequency range). If you detect any problems, these are

definitely caused by the system itself and should not be fixed with an equalizer!

Finally, use the ULTRA-Q PRO to fine-tune the system.

+ If extreme equalizer settings are necessary to achieve a usable frequency response, the alarm

bell should start ringing!

This does not mean that such settings should generally not be used, often enough they cannot be avoided if

the room acoustics are poor. Nevertheless, you should always try to change the room acoustics before you

start tweaking the response curve drastically.

Once the basic setting has been found, you can fine-tune the system using music and speech signals. If you

own a so-called real-time analyzer (RTA) make sure that the measuring microphone is properly positioned. It

should be placed directly within the dispersion field of the sound system without being disturbed by acoustic

characteristics of the room. Avoid placing it behind curtains, less than 1 m away from the walls, or on an open

balcony, as this would impair your measurements.

We recommend that you move the measuring mic on a circular line in front of the stage, so that you can

compare the measured results. In this context it should be made sure that the frequency response diagrams

do not differ excessively from each other. If you encounter any problems, change the position of the measuring

mic or check the system for proper phase.

Please verify that any background noise is at least 6 dB (better 10 dB) lower in level than your operating level;

otherwise you cannot trust your measurements!

Once the system has been adjusted as accurately as possible to yield the desired response curve, walk

around in the audience area and listen to the sound produced at various places. Remember to give your hearing

some pauses during the test and use different music or speech programs, so that you get a feel for the

response characteristics of the sound system.

It takes a lot of time and patience to set up an equalizer properly!

Additionally, you could experiment with a stage or house microphones directly connected to the analyzer, as

this will give you some clues as to local reflections, acoustic resonances and the lateral dispersion character-

istics of the speakers. Once the overall adjustment of the sound system has been completed, any further

corrections should not be made on the system itself but in the respective channels of the mixing console, in

particular, when you find that certain microphones are susceptible to feedback.

8. SPECIAL APPLICATIONS

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Audiovox PEQ-200 User Manual Page 18

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