2
A Few Words About Enclosures
Your Decade Series subwoofer requires
an enclosure to realize its full low-
frequency response. The speaker’s design
is flexible enough to produce exceptional
results no matter whether you specify a
small sealed, vented or bandpass enclo-
sure. In vented and bandpass enclosures,
box size and port tuning frequency will
also help dictate the low-frequency
performance and output capability of
your system.
Your Decade Series subwoofer will also
work in infinite baffle applications where
there is no space or budget to build a
box. Be aware that infinite baffle or “free
air” mounting will reduce the power han-
dling of any subwoofer compared to an
application using an enclosure.
Finally, any deviation from recommended
enclosure volumes or port dimensions
should be made using dedicated
enclosure-design software, such as JBL
Speakershop™. If this type of software is
not available to you, look for assistance
on JBL’s Web site at www.jbl.com or from
your authorized JBL dealer.
Your Car and Bass Reproduction
Depending on the size of the vehicle’s
interior listening space, reproduced
frequencies below 80Hz are actually
boosted by nearly 12dB per octave as
frequency decreases. NOTE: This effect,
known as the vehicle’s transfer function,
plays an important part in shaping the
overall in-car response and is displayed
graphically along with freespace
response on the enclosed data sheet for
your Decade Series subwoofer.
Enclosure Calculations and
Building Boxes
Use the recommended box designs on
the enclosed data sheet. Choose cabinet
dimensions to fit your vehicle, but do not
change the enclosure’s volume. Doing so
will change the tuning frequency of the
enclosure and may adversely affect final
performance. If you cannot perform the
necessary calculations yourself, please
contact your authorized JBL dealer for
help and for information about JBL
Speakershop, a dedicated enclosure-
design software program for experienced
car-audio enthusiasts.
In addition, there are a number of points
you’ll want to keep in mind as you con-
struct an enclosure:
1. Use 3/4" (19mm) MDF (medium-density
fiberboard) or marine birch plywood to
build an enclosure. Enclosures for 12"
and larger subwoofers, or small sub-
woofers driven by high power ampli-
fiers, should be constructed using 1"
(25mm) material.
2. Seal all joints with glue and screws; do
not use nails. We recommend “deck” or
“zip” screws since they have coarse
threads for better grip and don’t require
pre-drilling holes. Once the box has
been tested, seal all interior joints with
silicone caulk.
3. Depending on the application, fill the
enclosure according to the design you
have chosen from the enclosed data
sheet in one of three ways: zero-percent
fill (i.e., no fill), 50-percent fill (i.e.,
1"-thick polyfill sheets on all inside
walls except where subwoofer is
mounted), or 100-percent fill (i.e., entire
box is stuffed with loosely packed poly-
ester fiberfill).
Thank you for choosing a JBL Decade™
Series subwoofer. Decade Series sub-
woofers are designed to suit a broad
range of mobile-audio applications and
can be used in a wide variety of enclo-
sure types to produce extended, powerful
bass in a limited amount of vehicle
space. To ensure maximum subwoofer
performance, we strongly recommend
that installation be left to a qualified pro-
fessional. Although these instructions
explain how to install a JBL Decade
Series subwoofer in a general sense, they
do not show box construction details and
exact installation methods for your partic-
ular vehicle. If you do not feel you have
experience, do not attempt the installa-
tion yourself, but instead ask your autho-
rized JBL dealer about professional
installation options.
Remember to keep your sales receipt
with this manual in a safe place so both
are available for future reference.
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