P1280 - JBL Car Audio User Guide / Operation Manual. Page 2

02

for purchasing a new JBL

Power Series subwoofer. Subwoofer
installation often requires woodworking
skills and some experience disassembling
and reassembling automotive interiors. If
you lack the tools or necessary skills,
have your subwoofer installed by an
authorized JBL dealer. 

Warning: Playing loud music in an auto-
mobile 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.

Power Series subwoofers are optimized
to perform best in small sealed, vented
and prefabricated bandpass enclosures.
While infinite-baffle mounting of Power
Series subs is possible, power handling
will be greatly compromised because
there’s no enclosed volume of air to pre-
vent the speaker’s cone from moving past
its limit. For this reason, we do not rec-
ommend infinite-baffle mounting for
Power 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 move-
ment, 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, 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 effic i e n c y
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 han-
dling. 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. While there are
some prefabricated vented boxes avail-
able, matching a prefabricated box to a
particular woofer is difficult. If you wish to
use a vented enclosure, we strongly rec-

ommend 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 larg-
er than the optimum sealed box for the
same woofer and will require more space
inside the vehicle. 

Bandpass 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 bandpass enclosure.
Bandpass-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 enclosure described in the
enclosure design sheet included with the
woofer. Fortunately, there are many pre-
fabricated bandpass boxes available and
they are all optimized to extract the most
output possible from any woofer.
Bandpass enclosures can be quite large
and may require a lot of space inside your
vehicle.  

P-Series Subs Owner's Manual  6/15/99  10:18 AM  Page 2