JBL 6230 - 2.8 SPEAKER CABLES

will
be
6
dB too
loud
(four
times the
level
of
the
woofer).
Therefore,
the
crossover
network must
provide
6
dB
of
attenuation
for
the
compression
driver,
lowering
its
input
power
to 50
watts.
The
200 watt
amplifier
turns
out to be
perfectly
suited to
driv-
ing
this
system,
even
though
one
driver
is
rated
at just
50
watts.
2.8
SPEAKER CABLES
2.8.1 TYPE
OF WIRE
A
number
of
companies
offer
various
special
"speaker
cables"
which are
claimed to
vastly
improve
the
signal
delivered
from
amplifier
to
loudspeaker
system.
Without
going
into
great
details,
suffice it
to say
that
some
special
cables
have
merit,
others
may
actually be
detrimental,
and
overall
the value
will
have to
be
determined
by
the user.
In our
opinion, for
most
applications just
two factors
need to
be
considered:
DC
resist-
ance
and
durability.
Generally,
the
larger
the
wire gauge,
the
better.
DC
resis-
tance
is lower
with
larger
wire,
and hence
more of
the
amplifier
power gets to
the
loudspeaker
(and
damping factor
is
not
degrad-
ed;
see
Section 2.8.2).
More
strands of
wire in
a
given wire
gauge
are
beneficial
because
they
let
the cable
handle
more
flexing
without
fatigue.
2.8.2
DAMPING
FACTOR
The
higher
the damping
factor
of
an
amplifier,
the
greater
its
ability
to
control
unwanted
speaker
cone
movements
—
espec-
ially
at
low
frequencies.
Damping
factor
is easy
to
calculate;
divide the
speaker's
rated
load
impedance by
the
amplifier's
out-
put
source
impedance.
For
example,
an
amplifier
with
0.04
ohms
output
impedance
at
1 kHz
presents a
damping
factor of
200 to
an
8 ohm
speaker
(8
/
0.04
*
200).
To
understand
how a
high
damping
factor
improves
sound
quality,
one must
first
understand
the
underlying
principles.
When an
amplifier
drives
a
woofer,
current
flowing
through
the
voice
coil creates a
magnetic
field
which
interacts
with
the
permanent
magnetic
field
in the gap
and
forces
the
diaphragm/
voice
coil
assembly
to
move.
Consider what
happens
when
the
resting
cone
is accelerated
to a
maximum velocity
by a
signal
pulse;
the
maximum
signal
builds up,
and the
voice
coil/diaphragm
assembly
tracks
the
current,
moving
outward
proportionately.
When
the current
returns
to zero,
the
suspension
and the
air
mass
loading the
diaphragm
pull it
back
toward its
original
resting
position, and
momentum
tends to cause
overshoot
past
that
point.
In
the absence of
an
applied
signal,
the voice
coil
is
moving
through a
magnetic
field,
and
according to
basic
physical
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