Jbl L 250 1982 Brochure

Page 2

The L250 is the most advanced
loudspeaker JBL has ever built for
the home. JBL has spared no
effort necessary to meeting the
design goal: to buildthe most
accurate loudspeaker possible.

Accuracy. for JBL. encompasses
many factors. Tonal and transient
accuracy maintain the essential
character of music. High output
capability with low distortion
means wide dynamic range.
Accurate, stable imaging brings
the spatial qualities of live music
into the home.

The JBL L250 excels at all of
these aspects. The limiting per-
formance factors will be the
program source and associated
electronics. From the singular
shape of the enclosure to the
unique level controls. nothing has
been overlooked.

The woodworking complements
the engineering. Our cabinet-
makers finish each enclosure to
your order. by hand. In every
detail. the L250 is a definitive
expression of JBL qualify and
craftsmanship.

Tl-lE ENCLOSURE

Form follows function in the L250's
enclosure. Designed completely
around acoustical considerations.
it provides proper loading and
baffling for the drivers without
adding coloration of its own. The
asymmetrical shape minimizes
diffraction effects. as do the
rounded edges. The sloping front
baffle puts the drivers in correct
time and phase relationship as
well as correct vertical alignment.
To further assure a stable, three-
dimensional stereo image, the
L250$ are designed in mirror-

imaged pairs. Attention to all
these factors has produced the
L250's very open, transparent
sound. more often associated with
the live performance.

Enclosure construction is of 3/4-
inch high density particle board.
extensively braced to prevent any
resonances and lined with fiber-
glass to damp unwanted internal
reflections. Separate subchambers
for the lower midrange and mid-
range drivers preclude any inter-
action with the other loudspeakers.
A ducted port tunes the response
of the low frequency driver.

THE FREQUENCH}

DlVlDlNO NETLUORH

An advanced, highly refined ver-
sion of JBLs high resolution
frequency dividing network contri-
butes greatly to the excellent
performance of the system. The
network is a first-order design with
6 GB per octave slopes for the
smoothest blending of the four
drivers. Such design is possible
because the drivers exhibit lin-
ear response well beyond the
ranges required of them in the
L250. Additionally, the net-
work employs conjugate cir-
cuits to level the impedance
of each driver, so that ac-
tual operation approaches
the theoretical ideal.

Most dividing networks
blur musical transients
because of the hystere-
sis effects of the large
capacitors necessary
for high power han-
dling. To improve res-
olution, JBL incorpo-
rated circuitry more
typical ol active high
frequency electron-
ics. Small. highly
linear, polypropyl-
ene and poly-
styrene "bypass"
capacitors, wired

in parallel with

the larger capacitors. enable the
network to pass transient waveforms
unaltered.