Handbook for Sound Engineers

1368 Chapter 35

cant measuring errors, especially with respect to the
repeatability of measurements. By refining the measure-
ment setup, using latest measurement technology, and
employing data averaging, as well as symmetry assump-
tions, the data acquisition can usually be improved by
an order of magnitude. In addition, it must be empha-
sized that the variation between samples of the same
loudspeaker model may be larger than the measuring
error. However, this depends strongly on the manufac-
turer and its level of quality control.

From the point of view of the simulation software,
the best-known practices should be assumed. There is
not much sense in limiting the capabilities of an
acoustic simulation package because of the quality of
the most inexpensive loudspeaker boxes. Like for the
geometrical and acoustic model of room, the “garbage

in, garbage out” principle holds true for the sound

system part of the room as well and the user must be

aware of that.

35.2.2 Receiver Simulation

For a complete acoustic model, the acoustic receivers

must also be considered. Most important for auralization

purposes is to account for the characteristics of the

human head and how it influences the sound that

reaches the inner ear. Often, simulation software pack-

ages also allow utilizing microphone directivity data, in

order to be able to image real-world measurement. How-

ever, it must be stated that in general the correct imple-

mentation of electroacoustic receivers has not nearly

received the same level of attention as the sources.

Figure 35-33. Directivity optimization with the prediction software EASE SpeakerLab. Left column shows frequency
response and vertical beamwidth of a two-way loudspeaker for initial crossover filter settings, right column shows optimized
frequency response and vertical beamwidth. LF unit (--), HF unit (- -), full-range (-).

Initial Linkwitz-Riley

Frequency Response

Final Asymmetrical Butterworth

Vertical Beamwidth Vertical Beamwidth

Frequency Response

10

5

0

5

10

15

20

25

30

Level—dB

32 63 125 250 500 1000 2000 4000 8000 16,000

Frequency—Hz

32 63 125 250 500 1000 2000 4000 8000 16,000

Frequency—Hz

Frequency—Hz FH

10

5

0

5

10

15

20

25

30

Level—dB

125 250 500 1000 2000 4000 8000 125 250 500 1000 2000 4000 8000

360

300

240

180

120

60

0

Beamwidth—

o

360

300

240

180

120

60

0

Beamwidth—

o