600 GTi - JBL Car Audio User Guide / Operation Manual. Page 8

frequencies. Because the 600GTi are
specifically designed for midbass
frequency operation, in a 4-way system as
described they should have their low and
high frequencies blocked by an active or
passive bandpass crossover in order to
achieve the best system fidelity and the
widest dynamic range.

For the best performance, we

recommend that an active crossover with
a minimum of 12dB per octave slope be
used for the transition point between the
Subwoofer and the 600GTi. The optimum
crossover frequency for this transition is
dependent on the specific components
used, the vehicle, and other installation
details. As a general rule, the crossover
frequency should be as low as possible
to achieve the best system imaging. You
can fine-tune the crossover after the
installation is complete for the best sound.
A good place to start your tuning process
is approximately 50Hz for the subwoofer
to midbass high-pass crossover point.
Higher crossover frequencies will allow the
speaker to play louder. Since no crossover
is perfect, it is advisable to keep your

crossover points away from the range
where your hearing is most sensitive.
Therefore we recommend that you try to
keep the low-pass frequency below
250Hz. This lets your full-range system
reproduce the frequencies covering the
most important vocal and lead instrument
fundamentals and their harmonics, which
will help optimize imaging.

If you prefer to use all passive

crossovers, you will need to construct or
purchase a band-pass filter for the desired
midbass frequency range and install it in-
line ahead of the 600GTi. Although the
wide range and smooth roll-off of the
600GTi allows the use of a simple 6dB per
octave filter, for the best system dynamic
range, we recommend that a minimum
slope of 12dB per octave be used.

The most advanced system designs

use active electronic crossovers such as
the JBL GTX2, GTX4 or GTX47 at both the
subwoofer to midbass transition point and
at the midbass-to-midrange transition. The
maximum recommended RMS amplifier
power routed directly to the 600GTi
is 300 watts.

The 600GTi Woofer/Midbass uses

many high strength materials which benefit
from a break-in period to achieve top per-
formance. The 600GTi will reach maximum
performance after playing for about one
hour at a moderate volume level.

As a result of their high efficiency,

all JBL loudspeakers will produce reason-
able volume levels in the automotive
environment using very little amplifier
power. However, the use of a low-powered
amplifier to attain very high volume levels
could lead to overdriving the amplifier. This
will generate high distortion levels which
can easily damage loudspeakers, 

even if

the rated power of the amplifier is below
the rated maximum power handling of the
loudspeaker!

As a general rule, do not turn up the

volume control past the point where you
hear distortion in the form of either signal
distortion from an overdriven amplifier or

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600 MANUAL/vs2.QXP  7/28/98 11:47 AM  Page 8