Handbook for Sound Engineers

1308 Chapter 34

response. In entertainment sound reinforcement systems,
equalization may also be used to enhance the sound
quality of, for example, a nasal-sounding performer’s
voice. This use of equalization is very different from the
other uses and, in general, it is better to avoid using the
same equalizer to both equalize the overall system and
provide enhancement of an individual performer.

34.5.2.2.2 What Equalization Can and Cannot Do

Equalization can make a well-designed system sound
subjectively better. It can improve intelligibility by
smoothing the frequency response or by deliberately
peaking response in the intelligibility frequencies
(approximately 1500–5000 Hz). Equalization can also
help minimize feedback caused by frequency-response
irregularities.
Equalization cannot make a poorly designed system
sound good. Equalization cannot significantly improve
the sound quality of poor-quality loudspeakers. Equal-
ization cannot affect the reverberation time in a room in
any way.

Equalization cannot significantly improve a feed-
back problem in a room where the PAG (potential
acoustic gain) is unacceptable. And equalization cannot
solve system response problems when those problems
are caused by signal alignment irregularities.

34.5.2.2.3 System Design Criteria for Equalization

Equalization should be the icing on the cake for a
well-designed system. A system to be equalized should
be designed using high-quality, low-distortion loud-
speakers and electronics with adequate head room. In a
multiloudspeaker system, solve any signal-alignment
problems before attempting to equalize the system (see
Section 34.3.2.11).

34.5.2.2.4 System Equipment

The system to be equalized must have an equalizer per-
manently installed in its signal chain. The equalizer must
remain in the system after the equalization process has
been performed and thus should be a high-quality device
with low distortion, low noise, and balanced input and
output. Filters should combine smoothly between sec-
tions. For a parametric, this can be accomplished by
using as broad a bandwidth as possible during equaliza-
tion and overlapping the bandwidth of adjacent filters
just enough to keep the electrical response smooth.

Commonly, the equalizer will be a module in a DSP.

Choose the module to meet the above criteria.

34.5.2.2.5 Test Equipment

Test equipment should include a calibrated,

flat-response microphone, a -octave real-time audio

spectrum analyzer, Fig.34-72, (often called a real-time ),

and a pink-noise generator. All equipment should be

high quality and properly calibrated. If available, a

sound level meter, with a flat response position, is use-

ful. Some meters have a line-level output and can thus

be used as the system test microphone, Fig. 34-73. Note

that newer, computer-based test instruments, such as

SIA Software’s SMAART system, Fig. 34-74, offer a

real-time analyzer function and may thus be used in the

equalization process.

Often, a house microphone is substituted for the cali-

brated microphone in the equalization process. This

allows the system response to be adjusted to compen-

sate for the response of the microphone as well as the

loudspeakers and the room acoustics. The house micro-

phone, however, should only be used when there is only

one type of microphone in the system (and all such

microphones have manufacturers’ response curves that

are very similar to each other).

If more than one type of microphone is used in the

system, either a separate equalizer must be used for

each type of microphone (indicating a separate mixer)

or the calibrated microphone should be used for the

Figure 34-72. A real-time, octave, audio spectrum

analyzer. Courtesy Gold Line.

(^1) » 3
(^1) » 3