JBL L7 Owners Manual
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Page 1
equal to that of the music's
complex frequency components.
lf a single speaker wire must con-
duct the full musical frequency
spectrum, this preponderance of
low frequency information can
interact with or modulote hþh
frequencies. The resulting
intermodulotion can create audible
changes to treble even before it
reaches your loudspeakers.
By using separate conductors
for high and low frequencies
(drawing L-C), unwanted treble
modulation is avoided. Bass
flows through one, treble
through anothen
Frequency-optimized cables
Having the opportunity to use
separate HF and LF cables, allows
you to employ conductors best
suited to each frequency range. As
previously noted, most amplifìer
power ís destined for your L7's
woofers, so upon first consider-
ation, ¡t would make sense to use
veq/ thick wire for LF connections
and tjrinner wire for HF
connections.
Howeve[the very fact that
treble is hþher in frequency, means
it is actually more sensitive to the
type and gauge of wire used. Hþh
frequencies are prone to
attenuation from a phenomenon
called skr:n effedt. High quality
speaker interconnect wires
minimize skin effect by employing a
large number of thin conductors
with very low oxygen content2.
Optimall¡you should use audio-
phile interconnects for both HF
and LF conductors. Howeven if
ydirr budget intervenes, use the
best quality speaker cables for the
high frequency connections and
plan to add better bass cables laæn
Amplifier flexibility
Bi-wiring also allows you the
option of using separute stereo
power amplifiers for left and rþht
L7 loudspeakers or even four
mono power amplifiers.
Using two stereo amplifiers '
(drawing L-D) can not only add
sonic improvements but upgrade
convenience as well. From a sound
standpoing dual amplifiers reduce
intermodulation between left and
right channels, since a complete set
of input and power supply circuits
are devoted to each speaker. Dual
amps also provide an e:Ny power
upgrade path: you can start out
lEeoors acaallyflo,,ralorgfie orærmostatorm of a wire, nthertJæn irside. The nrcre s.¡ráce aleâ, dæ less resbance to o-rrrern Tlns üre number cf indvidul conducors (conmbutírgin
Page 2
w¡th one stereo amplifìer; then add
a second one ldter to quadruple
POWer reseryes.
Three or four individual ampli-
fìers provide evñro¡u
possibilitíes, since you càn't¡3d ¿¡f-
ferent brands and types.of amps
for HF and LF power. Many seri-
ous listeners prefer the midrange
and treble sound quality produced
by tube amplifiers. Howeve¡ many
tube designs do not provide as
"tþht" a bass sound as solid state
models and often produce less
power3. Bi-wiring with separate
bass and treble amplifìers allows
use of both tube and solid state de-
signs, where each is most
desirable.
Whether you are using two or
four amplifiers, it is important to
use the same brand and power
rating to power like connections
on the L7's. ln facL since the cross-
over point for the L7's HF/LF
connections is l50H¿ using ampli-
fìers of the same power for both
woofer and midbass/midrange/
treble connections is recom-
mended. For example, in a
2-amplifier bi-wire hook-up, if you
are using a 200-watt Brand X amp
for the leftLT,use a matching 200-
watt Br¿nd X amp for the rþht L7.
Or if you'r:e powering the left L7
low frequency connection with a
1SO-watt BrandY amp and the high
frequencies with a 1S0-watt Brand
3
Ztube amplifier; use the same
types and brands of amplifiers for
respective rþht speaker HF and LF
connections.
Bi-wiring connections
Drawings L-G and L-H show
two bi-amplifìcation options: dual
stereo amplÍfìer and four-amplifier
modes.
IMPORÏANT
l. The €xt€rnal "strapping bars"
which normally connect the
L7s' HF and LF terminals MUST
BE REMOVED as shown in
Drawing LJ (on the next page)
BEFORE BI-WIRING
CONNECTIONSARE MADE.
2. NEVER CONNECTTWO
AMPLIFIER CHANNELSTO
THE SAME LOUDSPEAKER
WITHOUT FIRST REMOVING
THE STRAPPING BARS.
Operating two amplifier
channels with the L7 strapping
bars in place can seriously
damage the amplifìers!
3. lf your preamplifier has just one
set of stereo outputs, you will
tns c not to oy ú,"ttfrey cant There are some *perb ulbe amplifiers whió prwirle wery bit as mudr tþtnr-*as solidslãte des¡gns Howwer, úey are high power modeb and are very, VERY epersive Moderåt€ly"riced obe porver amplifurs tend to be nndenæly powered aswdL They midn be accepable forpowerír6de mldbesfmËrarrgd reble poni