JBL 6290 - Appropriately Rated Loads

Input
load
resistors,
If
required,
may
most
conveniently
be
attached
to
the
barrier
strip
connector
of
the
amplifier.
2.7
APPROPRIATELY
RATED
LOADS
2.7.1
IT
IS
THE
USER’S
RESPONSIBILITY
TO
AVOID
OVERPOWERING
It
is
essential
that
the
amplifier
be
used
with
loudspeakers
of
suitable
impedance
that
can
handle
the
amplifier’s
power
output.
We
realize
this
Is
not
always
easy
to
determine,
especially
since
speaker
power
ratings
have
not
been
standardized.
Nonetheless,
JBL
IS
NOT
RESPONSIBLE
FOR
DAMAGE
TO
LOUDSPEAKERS
RESULTING
FROM
OVERPOWERING.
Fuses
may
be
Inserted
in
series
with
the
loudspeaker
to
protect
against
overpowering,
though
the
fuse
value
must
be
chosen
with
care.
Ideally,
the
value
will
be
high
enough
that
the
fuse
does
not
limit
the
peak
power
capability
of
the
loudspeaker.
On
the
other
hand,
the
fuse
value
must
be
low
enough
for
the
fuse
to
actually
do
its
job.
It
takes
a
period
of
time
to
heat
the
fuse
element
enough
to
cause
it to
melt
and
break
the
circuit.
If
it
takes
too
long,
the
loudspeaker
may
go
first.
Obviously,
delayed
action
(slo-blo)
fuses
are
not
acceptable
for
use
here.
If
fuses
are
used,
consider-
ation
must
be
given
to
their
location.
Put
them
where
they
are
accessible
for
ease
of
replacement,
provide
clear
labelling
of
the
replacement
fuse
value,
and
place
spare
fuses
nearby.
2.7.2
MORE
ABOUT
LOUDSPEAKER
POWER
RATINGS
While
there
is
no
cut-and-dr
i
ed
method
to
establish
an
appropriate
amplifier
power
for
a
given
speaker
system,
certain
guidelines
do
exist.
If
a
loudspeaker
manufacturer
specifies
’’to
be
used
with
amplifiers
rated
at no
more
than
’x’
watts,"
then
neither
speaker
nor
amplifier
warranty
is
likely
to
cover
damage
if
a
larger
amplifier
is
used.
If
the
amplifier
power
Is
only
recommended,
or
if a
power
rating
is
given
without
mentioning
the
amplifier,
then
the
question
as
to
whether
the
amplifier
is
"safe"
becomes
more
difficult
to
answer.
Loudspeakers
usually
fail
due
to
one
of
two
factors:
thermal
or
mechanical
overload.
Thermal
overload
means
overheating,
and
is
almost
always
caused
by
applying
too
high
a
level
of
sustained,
average
power;
the
voice
coll
insulation
may
burn
and
short
circuit,
the
coil
may
deform
due
to
the
heating
and
scrape
in
the
gap,
and.
In
some
cases,
speaker
cones
have
been
known
to
burst
into
flame.
Mechanical
overload
means
excessive
d 1
aphragm/vo
1
ce
coll
travel.
A
single
very
high
power
transient,
especially
at
lower
frequencies,
can
literally
tear
a
loudspeaker
apart.
Sometimes
mechanical
over-
load Is
more
gradual,
with
the
voice
coll
"bottoming"
against
the
magnetic
assembly
until
It Is
deformed;
a
compression
driver
dia-
phragm
can
strike
the
phase
plug
and
shatter,
or
the
suspension
can
be
overextended
and
simply
tear
apart.
I
1-6