P1520e (serv.man9) - JBL Car Audio User Guide / Operation Manual. Page 3

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 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. Bandpass
enclosures can be quite large and may
require a lot of space inside your vehicle.

Enclosure construction
Please observe the following suggestions
when building an enclosure for POWER
subwoofers.

1. Choose an enclosure design from the

enclosure design Sheet included with your
subwoofer.

2. Use at least 19mm (3/4") MDF(Medium

Density Fiberboard) or marine birch
plywood to build the enclosure. Enclosure
for 30cm (12") and larger subwoofers and
smaller woofers driven by high-power
amplifiers should be constructed using
25mm (1") material

3. Join pieces of wood with glue and screws;

do not use nails. Once the box has been
tested, seal all joints inside the box with
silicone caulk.

4. Fill the enclosure with damping material

(dacron, fibreglass insulation or long-fiber
wool).

5. Use PVC or ABS plastic for ports. Keep in

mind that the openings at either end of the
port must be at least one port diameter
away from any obstruction.

6. Mount the woofer on the baffle and screw

it down tightly for an air-tight seal.

We, Harman Consumer International 
2, route de Tours
72500 Château-du-Loir
France

Emmanuel Millot
Harman Consumer International 
Château-du-Loir, France  01/02

declare in own responsibility, that the products 
described in this owner’s manual are in compliance 
with technical standards:

EN 50081-1:1992
EN 50082-1:1997

03

TM