Choosing an Enclosure
GTi Series subwoofers are optimized to
perform best in small sealed, vented and
bandpass enclosures. While infinite-baffle
mounting of GTi Series subs is possible,
power handling will be compromised since
there will be no enclosed volume of air
to help the speaker’s suspension control
the motion of the woofer’s cone. For this
reason, we do not recommend infinite-
baffle mounting for high-power applications.
You should choose the enclosure you’ll use
based on the type of music you listen to,
how much amplifier power you’ll use to
drive the subwoofer, and how much space
inside the vehicle you can devote to a
subwoofer enclosure. If you’ll be using your
GTi Series subwoofer for SPL competition,
please see the document titled “GTi as SPL
Competition Subwoofers” (included with
your woofer).
Because a sealed enclosure provides the
most control over the woofer’s movement, a
woofer mounted in a sealed enclosure will
handle more power at low frequencies than
a woofer mounted in another enclosure
type. Sealed enclosures provide more
accurate sonic reproduction than other
enclosure types, so they are well suited
to all types of music. Sealed-enclosure
construction is straightforward. An
optimum sealed enclosure is always smaller
than other types of enclosures that are
optimized for a particular speaker, so they
require the least space inside the vehicle.
Vented enclosures provide better efficiency
in the 40Hz – 60Hz range, but this
efficiency comes at the expense of sound
output in the lowest octave (below 40Hz)
and at the expense of some control and
power handling below box tuning. If you
are using a small amplifier, a vented box
will provide more 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. 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.
Bandpass enclosures can provide the
greatest 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 vented or bandpass
enclosure. Bandpass enclosure design is
very tricky and the aid of a computer and
enclosure design software is necessary if
you wish to design the enclosure yourself.
Like a vented enclosure, a bandpass
enclosure must be built exactly to the
specifications provided. Bandpass
enclosures can be quite large and may
require a lot of space inside your vehicle.
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