1350 Chapter 35
Types of Loudspeakers. The different tasks of sound
reinforcement engineering require different radiator
types. These differ as to size and shape of their enclo-
sures, the form of sound conduction, the types of
driving systems used, as well as arrangement and
combination of the same. In this way one obtains
different directional characteristics of sound radiation,
sound concentrations, sensitivities, transmission ranges,
and dimensions that facilitate solutions for diverse
applications or even enable them at all.
Among the simplest radiators are single loudspeakers
of smaller dimensions and ratings that are used in decen-
tralized information systems, for instance, for covering
large flat rooms or for producing room effects in multi-
purpose halls. The integration into a wall or an enclosure
of these loudspeakers avoids the acoustic short-circuit
usually seen with no baffle situations—suppressing the
pressure compensation between the front and rear sides
of the diaphragm. To this effect a baffle panel or an open
or closed box may be used, Fig. 35-13.
With a closed box one has to consider that the oscil-
lating part of the loudspeaker functions in one direction
against the relatively stiff air cushion of the box. Loud-
speakers for such compact boxes are for this reason
provided with an especially soft diaphragm suspension
so that they cannot be easily used for other purposes.
Acoustically more favorable are the conditions with
vented enclosures, the bass reflex boxes or phase reversal
boxes. Such box loudspeakers are nowadays used less as
decentralized broadband radiators, but increasingly for
high-power large-size loudspeaker arrays.
Another possibility for achieving a determined direc-
tional characteristic consists in the arrangement of
sound-conducting surfaces in front of the driving loud-
speaker system. Given that such arrangements are
mostly of hornlike design, they are named horn loud-
speakers. Because of the high characteristic sensitivity
and the high-directional characteristic, this radiator
design is very well suited for sound reinforcement in
big auditoriums where the desirable frequency range
and different target areas (coverage areas) require the
use of different types of radiation patterns.
For technical reasons it is not sensible to construct a
broadband horn for the overall transmission range. A
better solution is several horn loudspeakers comple-
menting each other.Bass Horns. Owing to the great dimensions involved,
the design of bass horns requires extensive compro-
mises. Practical models of bass horns receive a horn
shape, as a rule, only in one dimension, whereas at a
right angle to it, sound control is achieved by means of
parallel surfaces. The power-handling capacity of such
bass horns, which are mainly used in music or concert
systems, is about 100–500 VA.Medium-Frequency Horns. The greatest variety of
driver and horn designs is available for horn loud-
speakers for the medium-frequency range of about
300 Hz–3 kHz.
The drivers used are mostly dynamic pressure-
chamber systems connected to the horn proper by
means of a throat, the so-called throat-adapter.Treble Horns. For the upper frequency range, two main
types of horn loudspeakers are produced. These are the
horn radiators showing similar design characteristics as
the medium-frequency horns that function in the
frequency range from 1–10 kHz, and the special treble
loudspeakers (calotte horns) used for the frequency
range from 3–16 kHz.35.1.3.3 Loudspeaker Line, Sound Column and Line
Arrays with In-Line Arrangement of RadiatorsClassical Columns. For many tasks of sound reinforce-
ment engineering, one requires radiators capable ofFigure 35-12. Frequency response curve of a loudspeaker
at different mounting conditions. Ts is the reverberation
time of the hall.
Figure 35-13. Different measures for suppressing the
acoustic short circuit.
A. Baffle panel.
B. Closed box.C. Bass reflect box.
D. Transmission box.A. B. C. D.