JBL GT5-12 - Manual (Page 2)

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CHOOSING AN ENCLOSURE
W WA AR RN NIIN NG G:: Playing loud music
in an automobile can permanently
damage your hearing, as well as
hinder your ability to hear traffic.
We recommend listening at low
levels while driving. JBL accepts no
liability for hearing loss, bodily injury
or property damage resulting from
use or misuse of this product.
GT Series subwoofers are optimized
to perform best in small, sealed,
vented and prefabricated band-pass
enclosures. While infinite-baffle
mounting of GT Series subs is possi-
ble, power handling will be greatly
compromised because there’s no
enclosed volume of air to prevent
the speaker’s cone from moving
past its limit. For this reason, we
do not recommend infinite-baffle
mounting for GT Series subwoofers.
You should choose the enclosure
you will use based on the type of
music you listen to, how much
amplifier power you will use for the
subwoofer and how much space
inside the vehicle you can devote
to a subwoofer enclosure.
Because a sealed enclosure
provides the most control over
the woofer’s movement, a woofer
mounted in a sealed enclosure will
handle more power than a woofer
mounted in another enclosure type.
Sealed enclosures provide more-
accurate sonic reproduction than
other enclosure types when
mounted inside a vehicle, so they
are well suited to all types of music.
Sealed-enclosure construction is
straightforward, and there are many
prefabricated sealed enclosures
available. An optimum sealed
enclosure is always smaller than
other types of enclosures optimized
for a particular speaker, so they
require the smallest amount of
space inside the vehicle.
Vented enclosures provide better
efficiency in the 40Hz – 50Hz range,
but this efficiency comes at the
expense of sound in the lowest
octave (below 40Hz) and at the
expense of some control and power
handling at the lowest frequencies.
If you are using a small amplifier,
a vented box will provide more
perceived bass output from less
power. Vented enclosures are also
well suited to a variety of music
types. Because vented enclosures
require the volume of the enclosure
and the size of the port to have
a specific relationship with the
characteristics of the woofer, the
enclosure must be built exactly to
the specifications provided. While
there are some prefabricated
vented boxes available, matching
a prefabricated box to a particular
woofer is difficult. If you wish to
use a vented enclosure, we strongly
recommend having your authorized
JBL dealer build it or verify that your
design is correct if you wish to build
it yourself. An optimum vented
enclosure is always larger than the
optimum sealed box for the same
woofer and will require more space
inside the vehicle.
Band-pass enclosures often provide
the most output available from any
amplifier and subwoofer combination,
at the expense of sonic accuracy.
If sheer SPL (sound-pressure level)
is what you desire most, choose a
band-pass enclosure. Band-pass-
enclosure design is very tricky, and
the aid of a computer and enclosure
design software is necessary. If you
are an experienced installer or have
some woodworking experience,
you may wish to build the band-pass
enclosure described in the enclosure
design sheet included with this
woofer. Fortunately, there are many
prefabricated band-pass boxes
available, and they are all optimized
to extract the most output possible
from any woofer. Band-pass
enclosures can be quite large and
may require a lot of space inside
your vehicle.