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17

Figure E

Use 2-conductor stranded

type, insulated wire to connect
the 08GTi to it’s crossover, and
the crossover to the amplifier.  A
minimum wire gauge of 18AWG
is recommended, with larger size
suggested for wire runs longer
than 10 feet.

The polarity — the positive/

negative orientation of the con-
nections for every speaker to
amplifier connection must be
consistent from left to right chan-
nel to assure proper imaging and
optimum frequency response.
This does not mean that the

08GTi Owners Manual  9/17/98 4:17 PM  Page 17

08GTi should always be con-
nected in the same polarity as
the midrange however.  It is pos-
sible, that due to the difference
in the distance the sound travels
from the midrange to your ears
compared to the distance from
the tweeters in a typical system,
and the short wavelengths of
sound at the crossover frequen-
cy, that a connection where the
tweeters are connected in
reverse polarity from the other
drivers in the system may actu-
ally result in better sound.
Because there is no way to
accurately predict this before

installation, we recommend that
you try the connection both
ways, and leave it in the polarity
that gives the smoothest audible
transition between the midrange
and tweeter.  The JBL standard
for polarity marking uses the
solid red wire as positive (+) and
the black striped wire as nega-
tive (–).

There are a variety of sys-

tem options available with the
08GTi.  The simplest configura-
tion is to use the 08GTi 

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connected in parallel to a full
range speaker system.  Because
the 08GTi is specifically
designed for high frequency
operation, it must have low fre-
quencies blocked by electrical
means to prevent damage to the
speaker.  To facilitate this, the
08GTi is supplied with an in-line
12dB per octave 5kHz high-pass
filter.  We call this a “protection
network”.  This allows you to use
the 08GTi as an add-on to an
existing system by attaching the
supplied protection network in
parallel to the existing speakers,
and connecting the tweeters to

the output of the network as in
fig. A, B and E.  For this applica-
tion, no other network is neces-
sary.  A disadvantage of this
type of system is that the high
frequencies are not blocked from
the midrange drivers, making the
performance of this type of sys-
tem typically less accurate than
one where a full crossover is
used.

A better approach is a com-

plete low-pass or band pass filter
for the midrange driver, com-
bined with a high pass filter for
the tweeter.  When a matched
GTi Competition Series system is

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08GTi Owners Manual  9/17/98 4:17 PM  Page 19

used, the best crossover choice
is the laboratory-optimized, 
system-matched crossover which
is included with the 408GTi or
508GTi system.  If you have not
yet installed your components,
we suggest that you consult your
dealer for this system package.
When a crossover such as this
one is used, you do not use the
protection network as it will inter-
act with the main crossover in a
detrimental way.  It is also redun-
dant, the main crossover will per-
form all of the functions of the
protection network.  If the pack-
aged GTi system crossover is

not used, the protection network
should be used as the high-pass
element, and a 5kHz low-pass fil-
ter may be built or purchased to
connect in line with the midrange
driver.

The most advanced system

designs use active electronic
crossovers such as the JBL
GTX2 or GTX47.  When an
active crossover is used, the pro-
tection network is not used, you
should however install an in-line
fuse holder containing a 1.5A
fast acting fuse between the
power amplifier and the tweeter.
Set the crossover frequency at or

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