Pfannenberg Catalogue

Introduction
Types of sound generation
Sound capsule – electromagnetic sound generation
In the sound capsule, anchors connected to the membrane are
pre-magnetised by a permanent magnet. When a voltage is
applied, the membrane is stimulated to oscillate, generating sound
waves that are perceived as an audible tone. Despite its relatively
simple and compact structure, the sound capsule has a relatively
high efficiency level. For that reason this technology is often used
in appliances with small dimensions.
Loudspeaker – electro-dynamic sound generation
The electro-dynamic loudspeaker consists of a membrane
connected to a central oscillating coil. This coil is located within
the magnetic fi eld of a permanent magnet. If the voltage of the
signal to be transmitted is applied to this coil, an alternating
electromagnetic fi eld is generated that causes the membrane
to move and, hence, to generate sound pressure.
Various membranes (smaller or larger, softer or harder) and
different coils and permanent magnets are used,
depending on the frequency range. Electrodynamic loudspeakers
are ideally suited for generating high sound pressure.
Horn loudspeaker – electro-dynamic sound generation
The membrane in a horn loudspeaker acts on a very small space –
the pressure chamber. The velocity of the air particles is increased
in this pressure chamber due to its small cross-sectional size. This
principle increases effi ciency considerably in comparison to other
designs. Due to the high sound pressure, which can be attained
and the high frequency range that can be transmitted, horn loudspeakers
are ideal for the transmission of sound in large areas.
Horn loudspeakers are usually insensitive to weather and are
very robust.
Piezo-electric effect
At the heart of a piezo loudspeaker is a crystal. When a voltage
is applied to this crystal, it deforms as a result and is thus set in
motion. Piezo loudspeakers essentially transmit only higher
frequency ranges and are not suitable for penetrating through
obstructions such as walls. The advantage of these systems lies
in their high impedance and, therefore, low power consumption.
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