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leaving little or no power for the high frequencies. The
result can be severe amplifier clipping (distortion) of the
high-frequency material. By biamping the system, with
an electronic crossover, the high-frequency material can
be routed to its own power amplifier avoiding the clip-
ping problem. This results in an effective increase in
head room that is greater than that which would be
obtained by simply using a single power amplifier of
equal power output.
Another advantage of biamplification is that it does
not absorb amplifier power as a loudspeaker-level
passive crossover does. Biamplification, by removing
this loudspeaker-level crossover, improves the overall
system efficiency.
Improved damping factor is another advantage of
biamplification. The damping factor of a power ampli-
fier is a number found by dividing its load impedance
(the impedance of the loudspeakers) by the actual
output impedance of the amplifier, which will be very
low for a modern solid state power amplifier. An ampli-
fier with a high damping factor can exert a greater
control over the motions of a loudspeaker cone than an
amplifier with a low damping factor. Thus, a high
damping factor may improve the sound quality of a
system. A loudspeaker-level passive crossover lowers
the damping factor by inserting its impedance between
the amplifier and the loudspeakers. Removing the loud-
speaker-level passive crossover, and biamplifying the
system, can thus improve the damping factor.
Biamplification can lower distortion by increasing
head room as explained previously. However, if clipping
distortion occurs anyway, it may be less audible in a
biamplified system. In a conventional, nonbiamplified
system, the high-frequency harmonics generated by clip-
ping of a low-frequency transient are passed through the
loudspeaker-level crossover to the high-frequency loud-
speaker where they will be quite audible. In a biampli-
fied system, there is no crossover and no high-frequency
loudspeaker after the low-frequency power amplifier.
Thus, the clipped low-frequency signals and their
harmonics are restricted to the low-frequency loud-
speaker and, due to its poor high-frequency response,
the low-frequency loudspeaker attenuates the audibility
of these unwanted harmonics.
34.3.4.3 When to Use a Loudspeaker System with
Passive Crossover
In small sound systems where high sound levels aren’t
needed and economy is a major consideration, a loud-
speaker system with a traditional passive crossover net-
work may be the best choice. In addition, the crossover in
a packaged loudspeaker system from a manufacturer usu-
ally includes a certain amount of equalization designed to
improve the overall response of the loudspeakers. Biam-
plifying this system would require the addition of a
graphic or parametric equalizer and, perhaps, a signal
delay in addition to the additional power amplifier and
electronic crossover. Thus, it’s usually best to use the
manufacturer’s loudspeaker-level passive crossover in a
packaged system unless the manufacturer has made spe-
cific provision for biamplification and offers recom-
mended DSP settings for biamplified operation.34.3.4.4 Signal Alignment in a Loudspeaker Crossover
NetworkIn the crossover frequency range the output from the
loudspeaker system includes output from both the high-
and low-frequency components. If the arrival time, at
the listener’s ears, of the signal from the high-frequency
component differs from the arrival time of the signal
from the low-frequency component, significant fre-
quency response degradation can result near the cross-
over frequency.
The solution to this problem is to physically or elec-
tronically align the low- and high-frequency compo-
nents so that their signal arrivals coincide at the
listener’s ears.34.3.5 Protecting the Loudspeakers34.3.5.1 Loudspeaker Failure ModesThe discussions in this section apply equally to both
low-frequency cone-type loudspeakers and high-fre-
quency compression drivers.
Discounting manufacturing defects that may cause
random failures, loudspeakers normally fail from either
excessive average power or from excessive peak power
at low frequencies. Loudspeakers may also fail due to
materials aging, physical damage, weather-related dete-
rioration or damage from insects or other pests.
Excessive average power causes voice coil heating
and eventually voice coil failure (or failure of other
components in the voice coil area). Excessive
low-frequency peak power causes mechanical failure of
the loudspeaker due to overexcursion. The voice coil
may separate from the rest of the loudspeaker or the
loudspeaker cone (or driver diaphragm) may tear or
shatter. Protecting a loudspeaker, then, is primarily a