INSTRUCTION MANUAL
INTRODUCTION
JBL craftsmen have been involved in the art of sound for more than
a generation - signal and source, wood and fabric, transducers and
acoustics - all of it.
Today these craftsmen continue to perform to the most rigid
standards any craftsmen can submit to: those impose upon
themselves.
JBL loudspeakers are carefully engineered instruments, pains-
takingly crafted and assembled to watchmakers standards. JBL
enclosures express the excitement of creative design; they are ele-
gant, solid and flawlessly finished. JBL transducers and electronics
offer what has been characterized by devoted music listeners as
"the incomparable JBL sound".
By following the few simple suggestions contained in this booklet,
you can look forward to superb high fidelity reproduction that will
retain its clarity and realism year after year.
UNPACKING
The packing material of your L-Series speakers has been designed to
protect the loudspeakers from any damage due to rough handling
during shipment. We strongly suggest that you keep the packing
material for future purposes, in case you are moving or your
loudspeakers should require service.
PLACEMENT
The listening room and the location of the loudspeakers within the
room affects bass level and bass response, imaging, clarity and
overall quality of sound. No other single factor has the same level of
effect on the final sound quality. The acoustics of the listening room
are determined by the dimensions of the room, its construction and
the furnishings it contains. Rooms that have different dimensions
for ceiling height, length and width will give a more even, balanced
sound than rooms where the dimensions are equal to each other.
This is important, especially at low frequencies, as the room
dimensions determine the pattern of standing waves within the
jom.
Consult your JBL dealer for information regarding the use of pro-
ducts or materials designed to control certain acoustic problems
caused by room size, shape or construction. In many cases,
significant improvement in performance can be achieved by careful
attention to room acoustics.
Your JBL L-Series speakers are able to give a very satisfying sound
in a great variety of listening rooms when set up in an even sided
triangle with respect to the listener. However, a careful setup
procedure will always be rewarding, and for best results we
recommend placement well away from the boundaries of the room
with preferably minimum 0.75 m (30 in) distance to the wall behind
the speaker, and 0.75-1.0 m (30-40 in) distance to the side walls.
The "bookshelf-size L-Series speakers, L 20, L 40 and L 90 can
naturally be placed on a bookshelf or mounted on the wall by a
suitable bracket.
The best possible sound, however, is achieved if the speakers are
placed on rigid and open, preferably heavy stand of appropriate
height (40-60 cm for the L 20 and L 90, 20-40 cm for the L 40).
Suitable stands are available from your specialized JBL dealer.
If you wish to place your JBL L-Series loudspeaker on a bookshelf
please be aware that the port of the enclosures are placed on the
back. A small distance between the back of the loudspeaker and
the wall (2,5 cm, 1 in) will ensure that the port is working properly,
while a complete closing of the vent will have a minor, but audible
effect on the performance of the deep bass.
A good guideline to proper setup is to start concentrating on the
tonal balance of the sound, aiming for the most neutral production.
Is the bass too strong or too weak compared to the midrange and
treble? Moving the speakers around in relatively large steps,
(20-30 cm or 8-12 in) will change the perceived tonal balance.
When a satisfying balance is found, a proper sound stage and
stereo localization is developed by smaller movements of the
loudspeakers in combination with angling towards the listening
position.
The larger L-Series loudspeakers (L 90, L 100) come in mirror
imaged pairs, but not as specific left and right enclosures. We
strongly recommend experimentation in order to find the most
satisfying overall sound. Attention to every detail of the setup will be
beneficial in terms of improved sound quality.
Your authorized JBL L-Series dealer, will by happy to help you obtain
the best possible performance from you JBL L-Series speakers.
NOTE: New loudspeakers require a certain amount of "exercise"
before they perform their best. A steady level of performance is
achieved after 8-12 hours of operation, depending on the nature of
the music and the level. Should you want to speed up this process
you can use inter-station FM noise as a signal during periods where
you would normally not be listening to the speaker. Alternatively a
CD player on "Repeat" would be an appropriate signal source.
CONNECTIONS
IMPORTANT: When connecting or disconnecting loudspeakers from
an amplifier, the amplifier must be turned off. Making connections
while the amplifier is operating could seriously damage the loud-
speaker system and void the warranty. The amplifier must also be
turned off before connecting or disconnecting cables at the
amplifier or pre-amplifier inputs.
1 mm
2
(18 AWG) insulated wire is the minimum size recommended
for loudspeaker connections up to 5 meters (16 ft). Beyond this
distance, heavier gauge wire is recommended: 1.5 mm
2
(16 AWG)
up to 10 meter (30 ft) and 2 mm
2
(14 AWG) up to 20 meters (60 ft).
These recommendations are given as MINIMUM requirements, and
generally speaking, the speaker leads should be as short as
possible.
Speaker wire and interconnect cables are important components in
an audio system. With all other factors at an appropriate level of
quality the speaker cable and the interconnect cable can make
significant contributions to the perceived sound quality. Careful
selection of cable and interconnects can add or subtract marked
shadings in the tonal character. Likewise, different cables can have
quite a dramatic impact on the dynamic contrasts experienced by
listeners.
The same care that was given to the internal system wiring in the
JBL L-Series speakers should be afforded to the selection and
application of the cable that will connect the various components in
your system. Your JBL dealer has the experience and knowledge to
