Handbook for Sound Engineers

Sound System Design 1309

equalization process and mixer tone controls used to

adjust for different microphone types (a more reason-

able approach).

34.5.2.2.6 The Test Setup

Connect the pink-noise generator to a typical micro-

phone input (use a pad if necessary to connect a

line-level pink-noise generator to a microphone input).

Set all system tone controls to their flat positions, and

set the equalizer controls to flat. Place the real-time ana-

lyzer near the equalizer and place the test microphone in

a typical listening position. Avoid placing the micro-

phone directly on-axis of any individual loudspeaker,

Fig. 34-75.

Turn on the system and the pink-noise generator, and

using the sound-level meter in its flat and slow response

positions, set the system gain for the design level. That

is, if the system was designed for 90 dB with 10 dB of

head room, increase the system gain until the meter

reads 90 dB. If the system produces the proper output,

reduce the signal at least 10 dB so the system will not

go into clipping in any octave.

Turn on the real-time analyzer and observe the

response. Note any significant peaks or dips. Move the

test microphone to several different locations and note

the changes. If the analyzer has memories, these can be

used in comparing microphone positions. If the system

response changes radically from position to position or

has significant peaks or dips at any position, attend to

these problems before beginning the equalization

process.

34.5.2.2.7 The Equalization Process

To equalize the system, first adjust the high-frequency

and low-frequency power amplifiers (in a biamplified

system) for the flattest response as indicated on the

real-time analyzer. Begin the process of adjusting the

equalizer by observing the real-time analyzer and

choosing a frequency area that peaks above the rest of

the response curve. Using the equalizer, reduce the

response in this frequency area. In the beginning of the

process, avoid cutting or boosting any frequency more

than about 3 dB since later adjustments of adjacent fil-

ters may affect the earlier adjustment. Do the same at

any other significant peaking areas. If the system equal-

izer includes boost capabilities, boost carefully between

system peaks if you desire, being sure that you are not

Figure 34-73. Precision integrating sound-level meters and
accessory filter sets. Courtesy Brüel & Kjaer Instruments, Inc.

Figure 34-74. SMAART real-time analyzer function. Cour-
tesy EAW/SIA Software.

Figure 34-75. Equalization test setup diagram.

EQ noisePink

RTA

Amp