JBL 6290 - Page 14

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