JBL MkII automotive Benutzerhandbuch

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.