JBL L7 Guide de configuration
L7 Ovvneds
ManualSupplement
Sped<erPlacement
Bi-Wiring andB¡jAnplification
g' 3'
side-mounted
woofers faceinward
Drawing
L-B
- L7
position
frontview
é,
L7 Placement
Drawing
L-Aand
L-B
show
optimal
placement
foryourL7
loudspeakers.
Note thatthe
speakers'
side-mounted
woofers
should
beplaced
inwards
towards
thecenter
oftheroom.
Bi-wiring
TheL7's
outerconnection
Panel
and
internal
dividing
network
are
designed
sothatseparate
sets
of
speaker
cable
c¿nbe
attached
to
thewoofer(LF)
and
midrangd
treble(HF)portions
ofthedividing
networlcThis
confìguration
is
alledbi-wirîng.
Bi-wiring
can
provideseveral
sonic
advantages
and
considerably
moreflexibility
inpoweramplifier
selection.
Reduction of intermodulation
Themajority
ofcurrent
flowing
between
anamplifierand
speaker
is
devoted
to thereproduction
of
bass.
fnfrLæ"60%
or moreof an
amp's
powerisdestined
for the
woofers.
When current
flows
through
awire,
it produces
a
magnetic
fìeld
(EMF)which
expands
and
collapses
atarate
Drawing
L-A
- L7
position
topview
equalto thatofthe music's
complexfrequency
components.
lf
asinglespeakerwiremustcon-
ductthefullmusicalfrequency
spectrum,thispreponderance
of
lowfrequencyinformation
can
interactwith or modulotehþh
frequencies.Theresulting
intermodulotioncan
createaudible
changesto trebleevenbeforeit
reachesyourloudspeakers.
By
usingseparateconductors
for highandlowfrequencies
(drawingL-C),
unwantedtreble
modulationisavoided.Bass
flowsthrough
one,
treble
throughanothen
Frequency-optimized cables
Havingtheopportunityto use
separateHFand
LFcables,
allows
you
to employconductorsbest
suitedto eachfrequencyrange.As
previouslynoted,mostamplifìer
powerísdestinedfor yourL7's
woofers,
souponfirstconsider-
ation,¡twouldmakesenseto use
veq/
thickwirefor LF
connections
and
tjrinner
wire
for HF
connections.
Howeve[thevery
fact
that
trebleishþherinfrequency,means
it isactuallymoresensitiveto the
typeand
gauge
ofwire used. Hþh
frequencies
are
prone
to
attenuation
fromaphenomenon
calledskr:neffedt.
Highquality
speakerinterconnectwires
minimizeskin
effectby
employing
a
largenumber
ofthinconductors
withverylowoxygencontent2.
Optimall¡you
should
useaudio-
phileinterconnects
for bothHF
and
LFconductors.
Howevenif
ydirrbudget
intervenes,
usethe
best
quality
speaker
cables
for the
highfrequency
connectionsand
planto addbetterbass
cableslaæn
Amplifier flexibility
Bi-wiring
alsoallows
you
the
optionof using
separutestereo
poweramplifiers
for leftandrþht
L7loudspeakers
or even
four
monopoweramplifiers.
Using
two stereoamplifiers
'
(drawingL-D)cannotonlyadd
sonic
improvementsbutupgrade
convenience
aswell.From
asound
standpoing
dualamplifiersreduce
intermodulation
between
leftand
rightchannels,
since
acompleteset
ofinputand
power
supplycircuits
aredevoted
to eachspeaker.Dual
amps
also
provideane:Ny
power
upgrade
path:
youcanstartout
lEeoors acaallyflo,,ralorgfie orærmostatorm
ofawire,nthertJænirside.Thenrcres.¡rácealeâ,
dælessresbance
to o-rrrern Tlns ürenumbercf
indvidul conducors(conmbutírgin<reased
skin
area)bmore imporarn únn thejrindividt¿l
drUgtess
2O"¡6en isacommonimgrrÇ incopperwire.
The,lesso46ør, thebeaercon&ctivity. Zp cordb
cornpoea ofaecoot¡ic ouó ¡itó copper
(El?C)
andtasslffinrcre o46en contentúnn dre
o4rgeftft€ehi$ corìductlvÇcopper
(OF{Q used
h çecftilgeakerwire
Dra¡ving
L-F
- Four-AmpBi-Wire
DrawingL-C- One-Amp Bi-Wire
DrawingL-D -Two-Amp Bi-Wire
Stereotube amp
DrawingL-E
- Three-AmpBi-Wire
w¡thonestereoamplifìer;
thenadd
asecondoneldterto quadruple
POWer
reseryes.
Three
or fourindividual
ampli-
fìersprovide
evñro¡u
possibilitíes,sinceyou
càn't¡3d¿¡f-
ferent
brandsandtypes.ofamps
for HFand
LFpower.
Many
seri-
ouslisteners
prefer
themidrange
andtreblesoundquality
produced
bytubeamplifiers.Howeve¡
many
tubedesignsdonotprovide
as
"tþht" abasssoundassolid
state
models
andoften
produce
less
power3.
Bi-wiringwith separate
bassandtrebleamplifìers
allows
useof bothtubeandsolid
statede-
signs,whereeachismost
desirable.
Whetheryouareusing
two or
fouramplifiers,it isimportant
to
usethesamebrand
and
power
ratingto powerlike
connections
onthe L7's.
lnfacL
sincethecross-
overpointfor the L7'sHF/LF
connectionsisl50H¿using
ampli-
fìersofthe samepowerfor both
wooferand
midbass/midrange/
trebleconnectionsisrecom-
mended.Forexample,
ina
2-amplifier
bi-wirehook-up,ifyou
areusing
a200-wattBrand
X amp
fortheleftLT,useamatching
200-
watt Br¿ndX ampfor therþht L7.
Or ifyou'r:epowering
theleftL7
lowfrequencyconnection
witha
1SO-wattBrandYampand
thehigh
frequencieswith a 1S0-wattBrand
3
Ztube amplifier;
usethesame
typesand
brandsofamplifiers
for
respective
rþht speakerHF
andLF
connections.
Bi-wiring connections
Drawings
L-GandL-Hshow
two bi-amplifìcation
options:dual
stereoamplÍfìer
andfour-amplifier
modes.
IMPORÏANT
l. The€xt€rnal
"strapping
bars"
which
normallyconnect
the
L7s'
HFandLFterminals
MUST
BEREMOVED
asshownin
Drawing
LJ (onthe nextpage)
BEFORE
BI-WIRING
CONNECTIONSARE
MADE.
2. NEVER
CONNECTTWO
AMPLIFIER
CHANNELSTO
THESAMELOUDSPEAKER
WITHOUT FIRST
REMOVING
THESTRAPPING
BARS.
Operating
two amplifier
channels
with the L7strapping
barsinplace
can
seriously
damage
the amplifìers!
3. lfyourpreamplifier
has
just
one
setof stereooutputs,youwill
tns c not to oy ú,"ttfrey cant Therearesome
*perb ulbeamplifiers
whió prwirle wery bitas
mudr tþtnr-*as solidslãtedes¡gns
Howwer,
úey arehighpower modebandarevery,VERY
epersive Moderåt€ly"ricedobe porver
amplifurs
tendto benndenæly powered
aswdL Theymidn
beaccepableforpowerír6de mldbesfmËrarrgd
reble poni<rn
of tÍ-wired L7s,hft\ rc'rildnor, in
o.¡roFinitxrbeúæbestdrcicefor lo¡¿bass
reproduaÍcninabi-wiredsFternwhidt willb€
$þ ærealt*ícconcerttnll leveh
DrawingL-G-Two Amp Bi-Wire Detail
Hook-upisidenticalfor
bothL7
speakers
Drawing
L-H- Four-AmpHook-Up Detail
need
to use
"Y' cordsinthe
three-amp
and
four-ampbLwire
hook-ups.
"Y'cordsare
available
from manysources
i¡cluding
your
JBL
dealer.
lfi,oú
häve
hookedupyour L7's
in.any
ofthebi-wireconfìgura-
tioÀs
indicated,it isnot
advisable
to useadditional
speakers,
eitherseparately
or
simultaneously.
Aswith conventional
one-
amplifier
connectionsshown
in
tlremain
LSeriesmanual,make
sure
thatallspeakercablesare
thesame
length.
Bi-amplification
Another adrancedoperation
alternative
is bktmplifuaion.
Instead
of beingdivided
byaninter-
nalcrossovecthefullfrequency
spectrum
isfikeredinto two
segments
bya2-wayocternal
elecuonic
crossoYen
whichiscon-
nectedbetween
the preamplifier
and
poweramplifiers.
Inbi-amplified
mode,the
LZs
woofer andmidrangdhigh-
frequency
transducersare
connected
direrlly
@separate
amplifiers.
Onlyaportion of the LZsinter-
naldividingnetworkisused.
The
wooferandmid-bæstransducer
section
ofthe crossoverareby-
passedviaaspecial
modification
which
canbe
performed
by
your
JBL
dealer.
Do notattemptto b¡-
amplifr
yourL7'swithouthaving
yourJBLdealerdotheproper
modification.
A suÍtable
elect¡onic
cnossover
rdt¡stbe
used.
Whilewe
dontdiscourage
bi-amplification,we
hastento note
ttrgtdre
LZsinærnd
crossover
is
difficukto
imprcve
on.ls phase
coherence,
freedom
fr'omdistor-
tionand
effciency
rinlevendte
finest
(and
most
o<pensive)
electroniccrctssoveß.
,_J
DrawingL-l
Rearof L 7 speakerwith
stapping
barc
disconnected
JBL
Consumer
Products,
lnc.
240Crossways
F¿rkWest,
WoodburyNY
¡1797
8500
BalboaBoulevard,
Northridge,
California
91329
(sr6)4e6-3400
H RHarman
InternationalCompany
PartNumber:739IG-L7A
Prinæd
inU.S,A"
ô6
Gó.,;r'
IO@"
+
o^
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