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In
order
for
manuf acturers
to
convey some real-world specifica-
tions about their products, they must have methods
to
attempt
simulation
of
real-world conditions.
One often used method
is
to use
pink noise and/or white noise techniques.
Pink noise
is
bandwidth
limited
random noise,
and
is
generally
used
as
a
simulation
of
"average program power;"
i.e.
the average power contained
in
a
typical musical sequence, whereas white noise
is
not limited to any
specific bandwidth
or
curve
and as
such,
contains more
high
frequency
energy.
These two test the thermal overload character
I
st
I
cs of
the
device.
Another test method
is
to
sweep
a
sine-wave through
part
or-
al
I
of
the audio spectrum.
While this method may cause
less
thermal
overload than the pink
or
white noise method.
It
can
cause
larger
excursions, particularly
at
low
frequencies.
This
is
a
good
test
of
the mechanical overload characteristics.
With compression drivers,
the mechanical power handling
capability
is
approximately quadrupled
simply
by
raising the minimum crossover frequency
by an
octave.
If
any
conclusion
can
be
drawn,
it
is
this:
NO
SINGLE POWER RATING REALLY DESCRIBES THE POWER HANDLING
CAPABILITY
OF ANY
LOUDSPEAKER
OR
LOUDSPEAKER SYSTEM.
ALSO,
WHEN
A
LOUDSPEAKER SYSTEM
IS
MULT
I
-AMPL
I
F
I
ED
,
I.e.
A
HIGH
FREQUENCY DRIVER
IS
CONNECTED DIRECTLY
TO THE
POWER AMP-
LIFIER OUTPUT,
A
SERIES PROTECTION CAPACITOR
IS
STRONGLY
RECOMMENDED
TO
REDUCE THE POSSIBILITY
OF
ACCIDENTAL DAMAGE
TO THE
DRIVER DIAPHRAGM.
CONSULT
THE
MANUFACTURER
OF THE
DRIVER
AND
HORN FOR RECOMMENDATIONS
ON
PROTECTION CAPACITOR
TYPES AND VALUES.
2.7.3
SOMETIMES
A
LARGER AMPLIFIER CAN
BE
SAFER
If
the desired sound
level
is
high enough to
require
a
low
power amplifier
to be
operated
into
clipping more
than
occasionally,
it
may
be
safer to use
a
larger
amplifier that
will
clip
less
frequently.
In
a
small amp
which
Is
clipping, the average output
power rises due to the increased signal density caused
by
distortion
components.
This increases thermal
and
mechanical stress
in
the
speaker because the clipped waveforms place greater
"G"
loads on
the
moving parts,
and
large
amounts
of
high frequency harmonics are
generated which
can
destroy the tweeter voice coils.
A
more powerful amplifier which
is
able to generate the desired
peak sound
level
without clipping avoids the
large increase
In
average power (thermal)
and
the high
acceleration (mechanical)
stresses caused
by
the
small
amplifier.
The major drawback
of
the
larger
amplifier
Is
that
it
can
produce higher peak outputs that
may
instantly destroy
a
loudspeaker.
Great care must
be
exercised
to
ensure that the amplifier
will
not
be
driven
at too high
a
level,
certainly never
into
clipping.
This can
be
accomplished either
by
knowing the program material
(if
recorded)
and
setting levels
accordingly,
or
by
using peak limiters (with
live or
unknown program
mater
i
a
I
)
.
I
1-7
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