JBL III SERIES Quick Start Manual
SERIES III SUBWOOFERS
THANK YOU for choosing a JBL
Series III subwoofer. These subwoofers
are designed to suit a broad range of car
audio applications and can be used in a
wide variety of enclosure types to produce
extended, powerful bass in a limited
amount of vehicle space. To get the most
performance from your new subwoofer, it
is strongly recommended that you have a
qualified professional install your
subwoofer. Although this manual does
provide general instructions about
installing these Series subwoofers, it does
not include enclosure construction details
or exact installation methods for any
particular vehicle. If you do not feel that
you have the necessary experience, do not
attempt the installation yourself, but
instead ask your authorized JBL dealer
about professional installation options.
Remember to keep your sales receipt in a
safe place, along with this manual, so
that both are available for future
reference.
WARNING
Playing loud music in a vehicle can hinder
your ability to hear traffic and
permanently damage your hearing. The
maximum volume levels achievable by JBL
speakers when combined with high-power
amplification may exceed safe levels for
extended listening. Using low volume
levels is recommended when driving. JBL,
Inc. accepts no liability for hearing loss,
bodily injury, or property damage as a
result of use or misuse of this product.
REPRODUCING
BASS IN VEHICLES
Depending on the size of your vehicle’s
interior listening space, reproduced bass
frequencies below 80Hz will be boosted
by nearly 12dB per octave as frequency
decreases. This phenomenon, known as
the vehicle’s transfer function (or cabin
gain), plays an important role in shaping
the subwoofer’s frequency response in
your vehicle.
SUBWOOFER
ENCLOSURE TYPES
The subwoofers are designed to perform
best in moderately sized sealed
enclosures, vented enclosures and
prefabricated band-pass enclosures.
Infinite-baffle mounting is possible, but
the subwoofer’s mechanical power
handling will be reduced because there
will be no volume of air to stiffen the
subwoofer’s suspension and prevent
overexcursion. If you choose infinite-
baffle mounting, consider the RMS and
peak power-handling ratings to be half of
what is listed in the specifications in this
manual.
You should choose an enclosure type
based on the amount of cargo space you
can devote to the enclosure, the amount
of power you will use to drive your
subwoofer(s), and your listening habits.
handling at and above resonance, but
reduced mechanical power handling below
resonance. Since the subwoofer cone and
voice coil don’t move much at resonance,
airflow across the voice coil is minimized
and thermal power handling is reduced
slightly at resonance.
Vented enclosures provide better
efficiency in the 40Hz – 60Hz range, at
the expense of sound output in the lowest
octave (below 40Hz). The use of an
infrasonic filter is recommended with
vented enclosures. An optimum vented
enclosure for a Series subwoofer is larger
than an optimum sealed enclosure.
V
ENTED-
E
NCLOSURE
P
ERFORMANCE
A
DVANTAGES
• An optimum vented enclosure has
greater efficiency and higher output in
the 40Hz – 60Hz range than an optimum
sealed enclosure.
• An optimum vented enclosure provides a
greater sensation of bass than an
optimum sealed enclosure.
• A subwoofer in an optimum vented
enclosure will require less amplifier
power to achieve a given acoustic
output (down to the enclosure’s
resonance frequency) than in an
optimum sealed enclosure.
V
ENTED-
E
NCLOSURE PERFORMANCE
TRADE-OFFS
• Reduced output in the lowest octave
(below 40Hz).
• Reduced mechanical power handling
below the enclosure’s resonance
frequency. The use of an electronic
infrasonic filter is strongly recommend-
ed to reduce the chance of overdriving
the subwoofer below the enclosure’s
resonance frequency.
• An optimum vented enclosure will
always be larger than an optimum
sealed enclosure.
V
ENTED-
E
NCLOSURE
C
ONSTRUCTION
Vented-enclosure construction is more
difficult than the construction of a sealed
enclosure. The enclosure volume and port
dimensions have a specific relationship
with the physical and electromechanical
characteristics of the subwoofer,
requiring that the recommended
enclosure volume and port characteris-
tics be strictly observed. As with sealed
enclosures, use medium-density
fiberboard (MDF), glue and screws to
construct the enclosure, and seal all
joints with silicone caulk.
R
ECOMMENDATION
Subwoofers in vented enclosures are
recommended for enthusiasts who prefer
accentuated bass response, for those who
have plenty of cargo space to devote to a
subwoofer enclosure and for those who
will use a less powerful amplifier to drive
their subwoofer. The volume and port
dimensions indicated must be followed
precisely to ensure optimum
performance.
MOUNTING THE
SUBWOOFER
The subwoofers should be
mounted from the outside of the
enclosure. Use the included foam
mounting gasket to ensure a leak-free
seal between the subwoofer frame and
the enclosure.
CONNECTING THE
SUBWOOFER
S
ETTING THE
I
MPEDANCE
The Series III subwoofers both feature
the Selectable Smart Impedance
™
(SSI) switch. This exclusive feature lets
you set the subwoofer’s impedance to
either 2 ohms or 4 ohms with the flip of a
switch (see illustrations below). This
allows you to extract the most from your
subwoofer amplifier in any situation.
The SSI 2-ohm setting increases the
subwoofer’s output over the 4-ohm
setting by up to 3dB, depending on the
amplifier. Performance is identical in all
other respects. If the connected amplifier
is rated for 2-ohm operation and its 2-ohm
power ratings are within the subwoofer’s
power-handling specifications, setting
the SSI switch in the 2-ohm position will
achieve maximum output.
S
EALED
E
NCLOSURES
The air trapped inside a sealed enclosure
is compressed when the subwoofer moves
rearward and is rarefied when the
subwoofer moves forward. In both cases,
the air inside and outside the box will
seek equilibrium by pushing and pulling on
the subwoofer cone. The result is a
stiffer suspension when compared to the
subwoofer operating in free air. This
means that the subwoofer’s cone will be
harder to move at low frequencies, a
condition which protects the subwoofer
from physical overexcursion, but
requires more power than other designs
to achieve a given acoustic output.
S
EALED-
E
NCLOSURE
P
ERFORMANCE
A
DVANTAGES
• The in-vehicle performance will have
the flattest overall frequency response.
• The in-vehicle response will have the
widest bandwidth. (Usable low-frequency
response inside the vehicle will be
below 20Hz.)
• An optimum sealed enclosure will always
be smaller than an optimum enclosure of
another type.
S
EALED-
E
NCLOSURE
P
ERFORMANCE
T
RADE-OFFS
• An optimum sealed enclosure will have
lower overall efficiency than an
optimum enclosure of another type.
• A subwoofer in an optimum sealed
enclosure will require more amplifier
power to achieve a given acoustic
output than in an optimum enclosure of
another type.
S
EALED-
E
NCLOSURE
C
ONSTRUCTION
Sealed-enclosure construction is straight-
forward and forgiving of errors in volume
calculation, but air leaks should be
avoided. Use medium-density fiberboard
(MDF), glue and screws to construct the
enclosure, and seal all joints with silicone
caulk.
R
ECOMMENDATION
Subwoofers in sealed enclosures are
recommended for enthusiasts who prefer
accurate music reproduction and flat
frequency response, for those who have a
smaller space to devote to a subwoofer
enclosure, and for those who have plenty
of amplifier power devoted to driving the
subwoofer. The sealed-enclosure design
indicated in this manual represents the
best compromise between low-frequency
extension and flat response.
V
ENTED
E
NCLOSURES
A vented enclosure acts like a sealed
enclosure at frequencies above its tuned
(resonance) frequency. At resonance
(which is defined by the vent), the vent
produces the majority of sound – the
subwoofer cone is nearly stationary while
the air inside the vent vibrates. This
provides greater mechanical power
2-Ohm Setting
4-Ohm Setting