JBL D208H User manual

Contents Page
Inlroduclion 1
PowerCapacity 2
AmplifierConnection 2
BassLoudspeakers 3
Midrange And
HighFrequencyDrivers 6
HornsAndAcousticLenses 9
FrequencyDividingNetworks 13
Service 25
JBLcontinuallyengagesinresearchrelatedtoproductimprovementNewmaterials,
productionmethodsanddesign relinements are introducedinto existingproductswithout
noticeas a routineexpression ol thatphilosophy.Forthis reason, anycurrent JBL product
maydillerinsomerespectfrom its publisheddescriptionbutwillalwaysequal or exceed
theoriginaldesignspecificationsunlessotherwiseslated.

Excellence isan elusivequality It'sso easy to recognize yetso difficult
toattain
JBLcraftsmenhavebeeninvolved intheartof sound (or morethan
agenerationsignal and source,wood and fabric,transducers and
acoustics—all ofit
Todaythesecraftsmencontinue to perform tothe mostrigidstandards
anycraftsman can submit to: thosetheyimposeuponthemselves.
JBLloudspeakers are carefullyengineeredinstruments,painstakingly
craftedandassembled to watchmakers'standards. JBL enclosures
express the excitement of creativedesign;they are elegant,solid and
flawlesslyfinished. JBL transducersandelectronicsofferwhat has been
characterizedbydevotedmusiclistenersastheincomparableJBLsound.'
Byfollowing thefew simplesuggestionscontained in thisbooklet,
you can lookforward to superbhighfidelityreproductionthatwillretain
itsclarityandrealismyearafteryear.
Introduction
Every JBL loudspeakersystem isthe product of extensivelistening
evaluationcombinedv/ithexhaustiveresearch and testing,using the most
sophisticatedequipment and methodsavailable. JBL systemrecommen-
dations are based on subjectiveevaluation of componentperformance
aswell as efficiency and eleclricalcharacteristicsTheseandothercritical
factorsmust be integrated bya frequencydividingnetworkengineered
for the specificcomponents ofthe system
Awell-built,sturdyenclosure is essential for optimumbassperformance.
Anenclosurehaving the properinternalvolume and tuning forthe loud-
speakerincreases low frequencydynamicrangeandimprovestonal
quality: it alsoreducesdistortionand the possibility ol overdriving the
loudspeaker.
Detailedguidance on enclosureconstruction maybe obtainedfrom
your JBL LoudspeakerComponentsdealer who mayalsosupply the
JBLEnclosureConstruction Kit.An illustratedbrochurewith a discussion
ofloudspeakertheory as woll as detailedenclosureconstructiontuning
andfinishinginstructions for homeentertainment and musicalinstrument
applications is contained inthekit Actualconstructiondrawings and
"LoudspeakerComponents by JBL'nameplates for yourfinished
enclosures are alsoincluded.
JBLtransducersareprecisioninstrumentsrespondingwithhighaccuracy
to the variations in electricalcurrentproduced by othercomponents in
themusicsystemExtraneousnoises,such as hum.rumble,crackling
orhissing donot originate inthe loudspeakers If youexperiencedifficulty
realizing the fineperformancebuiltintoyour JBL components,consult
the JBL LoudspeakerComponentsdealerfromwhomtheywere
purchased. Heis equippedwith the knowledgerequired to provideexpert
adviceandassistance. If.for somereason,yourJBLdealer is unable to
assistyou, or youcannotfind the answeryouneedpublished inJBL
literature,writedirectly to theJBLTechnicalServicesDepartmentdescrib-
ing the difficulty in detail:please be certainthatyourreturnaddress and
telephonenumberareclearlyprinted on yourcorrespondence.
1

PowerCapacity
Thespecifiedpowercapacityindicates the continuousprogrampower
levelthat canbe acceptedwithoutdamage. The peakpowercapacity is
considerablygreaterthan the continuousratedvalue, as indicated bythe
remarkabletransientresponse ofJBL loudspeakersystemcomponents.
JBLloudspeakerswillreproducecleansound at comfortablelistening
levelswhendriven byan amplifierhaving an output ofas little as10 watts
continuoussinewave per channel)However, for reproduction ofthe full
dynamicrange of contemporaryrecordings at highvolume, a morepower-
ful, qualityamplifierwillprovideoptimumperformance.Individual,fullrange
orextendedrangeloudspeakers, or loudspeakersinstalled in systems
rated upto50 wattscontinuousprogram maybe driven byan amplifier
delivering upto75 wattscontinuoussinewave per channel;thosehaving
aratedpowercapacity of50 wattscontinuousprogram or greater maybe
usedwith an amplifierdelivering upto150 wattscontinuoussinewave per
channel. Such an amplifier hasthe reservepowernecessary for accurate
reproduction of transients,which can reachmomentarypeaksequivalent to
tentimes the averagepowerlevel, inany case, an amplifiershould be
chosenwith an outputpowerralingthatisgreaterthan the maximumpower
thatwill be used.Thismargin of reservepowerwillhelpensurethat the
amplifierwill not attempttodelivermorepowerthanitsdesignallows.When
overdriven,mostamplifierswillclipsignalwaveforms, a condition of severe
distortionwhich is particularlydangerous to highfrequencyradiators.
Ifdistortion is heard, oneor more ofthe soundsystemcomponents is
operatingbeyond its capacity(assumingeachcomponent is properly
adjusted) andthe overallvolumelevel ofthe soundsystemshould be
reduced. In almost all cases, the acousticlevelgenerated byaJBL
loudspeakerwillbecomenoticeablydiscomforting totheear before the
loudspeaker can becomedamaged by excessivepowerfrom the amplifier.
There is virtually no danger of damaging a JBL loudspeaker ifit isoperated
within the followingguidelines: I)the signalfrom the amplifier,regardless
of its ratedpower, isnot distorted; 2)the amplifier isnot drivenintoclipping
(anotherform of distortionwhichoccurswhen the poweroutputlimitations
of the amplifiercircuitry are exceeded): and3)the powercord or audio
connectors arenot inserted or unpluggedwhile the amplifier is operating.
However, a powerfulwiderangeamplifier can accidentallydamage any
loudspeakerundercertainconditions. For example,rewinding a tape
recorderwith the playbackvolumeturned upcan generate"squeals"
powerfulenough to burn outthe highfrequencyunit.Similarly,powerful
lowfrequencypulsesextendingdowninto the subsonicrange can
eventuallydamage thelow frequencyloudspeaker. Ifthe phonograph
pickup is accidentallydroppedwith the volumecontrolfull up.orifthe
system is playedveryloudlywithexcessivebassboost,nearly the fullrated
power ofthe amplifier canbe channeledintodangeroussubsonicenergy.
AmplifierConnection
Important: Whenconnecting or disconnecting an extended or fullrange
loudspeaker, ora completeloudspeakersystemfrom an amplifier, the
amplifiermust be turned off. Makingconnectionswhile the amplifier is
operatingcouldseriouslydamage the loudspeakers and void the warranty.
1. The continuoussinewaverating of amplifierpower isthe moststringentmethod
currentlyused inthe audioindustry.Notethatmanyamplifiermanufacturers usethe
term"wattsrms" asa directequivalent tothe moremeaningful"wattscontinuous
sinewave'.'

Forconnections upto15m (50 ft). 1 mm(#18 AWG)insulatedwire
(ordinaryhouseholdlampcord) isthe minimumsizerecommended. For
longerdistances,werecommend the followingminimumsizes: 1.3mm
(#16 AWG)upto30m (100 It),and 1.6mm (#14AWG) upto60m (200ft).
Iflampcord is used, wires canbe differentiated by notingthat oneofthe
insulatingjackets is smooth,while the other hasa distinctridge.
Locate the loudspeakeroutputterminals onthe back ofthe receiver or
poweramplifier For eachloudspeakersystem,connectthe"black"wire to
theamplifieroutputterminallabeled"common:'"ground" or(-),andthe
"red" wire tothe remaining8-ohmspeakeroutput? The specified8-ohm
impedanceraling isa nominalfigurewhichsuggests a connectiongiving
themostefficientpowertranslerbetweenamplifier and loudspeakersystem
Notethatmanyamplifiershave a chassisgroundingterminalwhich is
usuallyseparatedfrom the otherconnectors.Thisshould notbe confused
withthe"ground"designationsometimesused to describe oneofthetwo
terminals for eachloudspeakerconnection.
BassLoudspeakers
It is goodpractice to keep a loudspeaker inits originalcarton or placed
facedown ona cleansurfaceuntilinstalled in order to preventaccidental
conedamage.Thealuminumcenterdome otan extendedrangeloud
speaker is particularlyfragileandshould notbe touched. A grille onthe
front ofthe enclosurewillrestrain the curiousoncetheloudspeaker
systemiscomplete
Mounting InAn Enclosure Widestsounddistributionwill be realized
andresponsethrough the midrangeregionwill be just a littlemorenatural
andtransparentwhen a loudspeaker is mounted tothe front,ratherthan
backsurface ofthe bafflepanel.Use of T-nutsandmachinescrews,
providedwithin the cartonpackingmaterial,allows the loudspeaker tobe
removed and reinstalledrepeatedlywithoutdamaging the enclosure. A
second, larger seiof hardware is supplied for rearmounting 300mm
(12 in) units.
Thesealbetween the loudspeakerframeandbafflepanelmustbeairtight
Whenfrontmounted,a seal is achieved by fitting the whitetubularvinyl
gasketinto a groove onthe back ofthe loudspeakerframe. (A flat, fiber
gasketissuppliedwiththeD208H.)Loudspeakersthat can berearmounted
areprovidedwith a facinggasket to form a seal. An airtightsealmustalso
bemaintainedwhere the inputwiresenter the enclosure.
Wheninstalling the loudspeaker,tighten the mountingscrewsevenly to
avoid the possibility of framewarpage.Avoidexcessiveforce;tighten the
screwsjustenough to prevent air leaksbetween the frame andthe
enclosure,
2Connectingbothspeakers as describedwillinsureproperin-phaseoperation:
i e.. iheirconeswillrespond toa monophonicsignal by movingsimultaneously in
thesamedirection,and not oppositetoeachotherInadvertentout-ol-phaseoperation
(whichoccurswhen onesetot speakerwires is reversedv/ithrespect to theother)
will not harm the system, but willcausesomeacousticalcancellationwhichwillhave
theaudibleeffect ol reducing low Iroquencyresponse.
3

AlthoughJBLloudspeakersareextremelyrugged,theconeand
othermovingpartsaresubjecttoaccidentaldamage.Exercise
extremecautionwheneverusinga screwdriverorothertoolsin
theirimmediatevicinity.
WallMountingTheD208HandLE8T-Hareshallowenoughtomount
betweenthestudsofmostroom walls. Werecommendthatyoubecertain
sufficientdepthexistswithinthewallbeforecuttingan opening. Whilewall
mountinginevitablycompromiseslowfrequencyperformancetosome
degree, excellentresuitscanstillbeachievedwhenspaceisnotavailable
fora conventional,portedenclosure.
MountingDimensions
Loudspeaker BattleCutoutDiameter Boll
Circle
Diymoior Frame
MourningHoie
DrillSize
T-Nut Or ISize
1' rontMount RearMounl Boll
Circle
Diymoior Frame
MourningHoie
DrillSize FrontMount RearMount
D208H 179 mm
7X,m
179 mm
7Vi.in
194 mm
7% in 5.4mm in 58 mm
m b8 mm
»1
LE8T-H
t79mm
7M,m
NoiRec-
ommended
194 mm
754in 54 mm
&in 5.8mm
J1
250mm
10-mch
??8mm
H Not
Ree
ommended 245mm 954in 54 mm (4>in 5.8mm
m
300mm
12-inch 281mm 11Vi«in
281 mm
11 Vi. in 294mm
11K.in
6 7 mm
•%.in 5.8mm #1 8mm 5i«in
360mm
14-inch 316mm
9mm NotRec-
ommended 337mm 13VJ in 6.4mm
5kin 58 mm Si
300mm
15-inch 355
mm"
13%in 343mm*
t3!4in
3.'Omm*
145i.in
71 mm
Ki m
5.8mm
'"it! " 8mm
Vie III
•WhenineMA'Sisused.Ihebalt-ecutoutdiametermaybeaslargeasI4V«in;363mm),andinebetìcircle
diameteris irati 16%in(416mm)toI6J4in(120mm}.T-nutdrills'2e>55<6in(8mm)
UseofTheMA15
TheMA15loudspeakerinstallationkitsimplifiestrontmountingandallowsgreater
latitudeinthediameterofthebafflecutout

InstallingA PassiveRadiatorA passiveradiator(unclionslike a port.
IIcanbeused,wherebattlespacepermits,totuneanenclosuretovery
lowfrequenciesbyvaryingthenumber of weightsattached to thecone
assembly.A passiveradiatorshouldbeusedonlywiththespecificlow
frequencyloudspeakersforwhich itis recommended.
Thepassiveradiatormustbeinstalledwiththeloudspeakerinanairtight
enclosure of therecommendedinternalvolume.Mountingdimensions
arethesameasfortheloudspeaker.Foroptimumperformance,placethe
twounitssidebyside;however,theycanbemountedinanyconfiguration
aslongastheyarenocloserthantwoinches(50mm)toeachother,and
notseparatedbymorethansixinches(150mm).Tworemovablemetal
discsareattachedtothecenter of thePR15CThefiberboarddiscinfronl
ofthemisintegraltothepassiveradiatorandmustnotberemoved.Each
ofthemetaldiscsweighs100grams.Sixfiberboarddiscsaresupplied in
thecarton;each of theseweighs20grams.
Thepassiveradiatormusthavethepropermassinorder lo tunean
enclosuretoIheresonantfrequencyofthelowfrequencyloudspeaker.This
chartprovidesa guidetotheuseofthePR15Cinitsusualapplications.
Tuning Chart for PRI5C
InstallIhonumberofdiscsindicated tor the
enclosurevolume Cm = metaldisc I= liberboarddisc)
Enclosure
Volume
Ures
GUSC =081
113 HI
142- 16D
5 1-St)
170- jjjg •QS-??b
7- B0
Used with
LEMH.LE15H 3t 21 11 o-
Used with
12-11! 136H
1 m • • (
1m _ _
•Da noiristai mvoJÙW scre.v
Tuning A PassiveRadiator
Whenadding or removingluningdiscs,becertainlhatthehardware is inihe
sequenceshownTightenIhemachinescrewonlyenough lo holdIhediscsand
washerssnuglyinplace.

Fine TuningAnEnclosure If you are usingthedetailedplanscontained
intheJBLEnclosureConstructionKit,followtheportinginformation
provided; it hasbeenvalidated bytheJBL engineering stafl. When
constructing an enclosure of your own design,use of the portingchart for
homeentertainmentloudspeakers(included in theJBLEnclosure
Construction Kit) willresult in excellentbassreproduction.Sinceeach
recommendation in the chart is averaged for the range of enclosure
volumesindicated, the audioperfectionist may wish to furthertune his
enclosure in order to achieveoptimumbasspotential. The finetuning
procedureisalsousefulwhendealingwith an irregularlyshapedenclosure
forwhichcalculating the internalvolumewould be difficult.
Thefinetuningprocedure is described in theJBL EnclosureConstruc-
tion Kit. In mostinstances,following the portingchartwillresult in a
measuredtuningfrequencywithin 10% of the optimumrecommended for
theloudspeaker(seechartbelow), and therefore, the improvementrealized
bycompletingthefinetuningprocedure maynot always be audible.
Recommended TuningFrequency For
JBL Loudspeakers
fcncfosure
Model Description tuning
Frequency
124H 300
mm(12 in)lowfrequency
I36H 380 mm(15 in)lowfrequency 26Hz
LESI H
200 mmf8in]full range
LE10H 250 mm[10in) lowfrequency
LE14H 360 mmC14 in)lowfrequency 32Hz
LE15H 380 mm (15 in) lowfrequency
32Hz
D130H 380
mm (15 in)extended rango 45Hz
130H 380mm (15 in) lowfrequency
D208H
200mm (6in)extendedrange
55 Hz
I)systemtuning is hignerthanrecomn-eindcd forthe loudspeake'covai a portun pithenon or lengthen ihe duct
il oneIs used.Conversely, if systemluniityidkJwarthanrecommendedma«o1r-<jpertterser or ahoitanIliaduel.
Whentuning a pass-vcradiator.beginwith'e^verwtTflv.ctgntsthanrecommended for ttteenclosurevolume Add
iveights J syslsmluning is higherIlarirecommendedremrjveweights it the systemtuning.ulortorthandesired
Apassivoradatcrcan be lemporantyrrounledinside PUT soihc luningweights are easilyaccessibleAdditional
washersused in conjunction winthe •/.eightssupplied vvitl aid in obtainingprecisetuning.
Midrange AndHighFrequencyDrivers
TheLE5H, LE21H, 075.and 077 mountdirectly tothe enclosurebaffle
panel, andcompressiondriversarebolted to theirappropriatehorns.Com-
ponentsandhornsintended for enclosuremounting are providedwith a
tubularvinylflangegasket foran airtightinstallation.Largefreestanding
horns, of course, donot requiresuch a gasket.
With the exception of freestandinghorns, a highfrequencyunit is
normallypositioned onthe bafflepaneldirectlyabove or below the bass
loudspeaker, and slightly tothe side if necessary to accommodatepanel
dimensions. If the distancebetween the pair of enclosures is limited, the
highfrequencyunitscan be mounted onthe outboardside of their
respectivebassloudspeakers;conversely, if the enclosures are further
apartthanaverage, the highfrequencyunitscan be mounted onthe

inboardside of Iheirrespectivebassunits. If Iheloudspeakersystemis to
havelow.midrangeandhighfrequencycomponents,placingthemin a
verticalline(low,midandhigh)willgenerallyprovidewidestandmost
uniformsounddistributionwithinthelisteningroom.Forbestacoustics,
componentsshouldbeasclosetogetheraspractical,butalleast50mm
(2in)aparttomaintainthestructuralintegrity of thebafflepanel
Positioningthehighfrequencydrivernear,ordirectingitsoutputtoward,
listenerearlevelwillusuallyresultinthemostrealisticperformance.
Caution: Topreventseriousdamage,neverconnecta midrange or high
frequencytransducerdirectlyloanysourcecapableofgeneratinglow
frequencysignals.Connectionshouldbemadeonlytotherespectivemid
orhighfrequencyterminals of therecommendedJBLfrequencydividing
network. If separateamplifiersareusedforthevariouscomponents of the
system(bi-amplification or tri-amplification). a properlydesignedhigh-pass
filtermustbeused-inadditiontoanelectronicfrequencydividingnetwork
-toprotectthetransducerfromturn-ontransientsandotheraccidental
lowfrequencysignals.
LE5H Midrange Transducer TheLE5Hmustbehousedinanisolated
sub-chambertopreventinteractionwiththelowfrequencyloudspeaker.
Forsmoothestfrequencyresponsethesub-chambershouldhave a
minimumvolume of 1.3litres(80 in3), andshouldbefilled lo moderate
densitywithfiberglassacousticdamping material. A sub-chambercan be
fabricatedof a tubehavinganinternaldiameter of 114mm (4 ft in)and a
length of 130mm(5in)flushmountedonthebafflepanelandclosedat
itsinteriorend.Inserttheinpulleadsthrough a smallholepunched in the
side of thetube(usecaulkingcompoundtomaintainanairtightseal),and
installthedampingmaterial.Pressthetubularvinylgaskelintothegroove
ontheback of themountingflange,connecttheinput leads, placetheLE5H
intothetubeandsecure it tothebafflepanelwiththefourself-tapping
screwsprovided.
LE21H HighFrequencyDirectRadiator TheLE21Hmountsdirectly to
thefront of thebafflepanelusingT-nutsandmachinescrewsThecutout
should be 105mm[AM in)indiameter,withadditionalclearanceprovided
fortheterminals(seethediagramonthenextpage).Theflatgasketonthe
rear of themountingflangewillformanairtight seal. PlacetheLE21H in
themountingcutoutandlightenthescrewsa littleat a time,maintaining
evenpressureonthegasket.Donotovertighten,
075And077 The075and077mountfromtherear of thebafflepanel in
an81mm(3?i«in)diametercutout:thedriverisheldinplacebyfour
machinescrewsextendingthroughthebafflepanel.Placethetubularvinyl
gasketaroundthehornandseat it againstthemountingbracketprior to
insertingtheunitintothebafflecutout.NOTE:The077shouldbemounted
withtheslot vortical, asshown,toprovidemaximumhorizontaldispersion.
The075producesa conicalsounddistributionpatternandneedsnopar-
ticularmountingorientation

I
105mm
Diameter
075,077MountingDimensions
075Or077Installation
Installthe077asshown,lorwidest
sounddistributioninthehorizontalplane. LE21HMountingDimensions

LEI75.LE85 And376Compression Drivers A compressiondriver
musi be bolted to theappropriatehighfrequencyhorn,which in turn, will
bemounted to thebafflepanel or freestanding ontop of theenclosure.
Bolts(%-20. 'Aè' hexhead)suppliedwiththedrivershould be tightened
evenly, and justenough to achieve a snug fit withoutovertightening. The
perforatedcentersection o( thefibergasket onthe matingsurface ofthe
drivermust be removedbeforeinstallation. It is goodpractice to cover the
exposedthroatopeningwithplasticelectricaltapewheneverthedriver is
notactuallyinstalled ona horn to preventforeignmatterfromentering
thedriver,particularlyironfilings or chipswhich canbe attracted bythe
strongmagneticfieldwhichexists in thedriverthroat
Horns AndAcousticLenses
Ahorn/lensassemblycouplestheoutput ofa compressiondriver tothe
air inthe listeningenvironmentandspreadsthesoundoutwardthroughout
theroom ina predeterminedpattern.Thesmallerhorn/lensassemblies
areusuallymounted to theenclosurebafflepanel; the largerhorn/lens
assemblieswill be freestanding ontop of theenclosure.
Caution: When a horn is mounted toa sturdybafflepanel of the recom-
mendedthickness, it will notbe necessary to supportthedriverHowever,
thedrivermust be separatelybraced or removedfrom the enclosure
whenevertheloudspeakersystem is transported,sinceundersuchcircum-
stances it is possible lor theweight of thedriver to pull the hornfrom
thebafflepanel.
HL87 Perforated-Plate Horn/Lens The HL87mountsfrom the front of
theenclosure ina 134mm (5%? in) diameterbafflecutout. Itis secured
byfourmachinescrewsandT-nuts.Aftermaking the bafflecutout,place
theHL87 in position anduse it asa pattern to mark the location ofthe
holes forthe mountingscrews.Thedrill bit sizerequired for theT-nuts
is 8 mm(Me in).
HL88 Perforated-Plate, HL89 SerpentineAnd HL90 Slant-Piate
Horn/Lens Assemblies Theselargehorn/lensassembliesmount ontop
of the enclosure.Themountingbracketsmust bo assembled tothe
horn/lens per theaccompanyingillustrations.TheHL89 is shownwith the
MA25installation kit, consisting of mountingbrackets anda bafflewhich
isrequired for optimumperformance. It is alsopossible to mountanHL89
ontheenclosurebafflepanelusing the cutoutillustrated.
HL91, HL92 And HL93 Slant-Plate Horn/Lens Assemblies The HL91.
HL92 and HL93mount on theenclosurebafflepanel, as illustrated- The
bafflecutout is108mm (4% in)in diameter.Countersink the four 7 mm
0& in) holes forthe flatheadmountingscrews The whitevinylringgasket
should be placed onthe hornmountingflange to insureanairtight seal.
(Continued on page 12.)

10

MountingThe HL91, 92And93
Thelensisaffixedtothefrontsurfaceofthepanelwithhook-and-pile
mounting tape. Whilethe"pile"stripsarestillattachedtothe"hook"
sectionsonthelens,removethepaperbackingtoexposetheadhesive,
placethelensinpositionoverthebaftlecutout,andpresstheadhesive
againstthepanel.Removethelensfromthetape(itnecessary,remove
thetapeas well, altermarkingitslocationonthebaffle)andpermanently
affixthetapetotheenclosurewithstaplesorsmallcarpettacks.Asthe
lensisremovedfromthetape,a "ripping"soundwillbeheard,indicating
normaldisengagement.
Aclearanceof67mm[2%in)betweenthebafflepanelandthegrille
assemblyisrequiredforthe lens. Thegrilleshouldwraparoundtheenclo-
suresothatbothsidesaswellasthefrontofthelensareunobstructed,
foroptimumsounddistribution.Ifthesidesoftheenclosuremustbecom-
pletely solid, a wedgebuiltupoffiberglassshouldbecementedinposition
oneithersideofthelens,runningthefullheightoftheenclosure.Ledges
atthetoporbottomofthebafflepanelshouldbetreatedin a similarmanner.
TopViewOfLensInstallation
12

254mm
10in
184rr.m
VA m
HL91, HL92 And HL93MountingDimensions
FrequencyDividingNetworks
JBLdividingnetworksprovideimperceptibledistribution of theaudiosignal
among the transducers ofthe loudspeakersystem. AllJBL networks are
engineered to match the exactcharacteristics of specificcomponents,
including the horn/lensassembly, as shown inthe NetworkSelection
Chart.We donot recommendusing JBL loudspeakersystemcomponents
inothercombinations or withthose of othermanufacturers.
Adjustment Each JBL dividingnetwork is providedwith a levelcontrol
thatpermitsmatchingloudspeakersystemperformance tothe acoustic
characteristics ofthe listeningroom andto listenerpreference. The control
regulates Ihe amount of power fed tothe highfrequencytransducer. It
does not affect the crossoverfrequency, nor does it limit the upper
frequencyresponse of theloudspeakersystem.
Adjustment of thelevelcontrolshould be madeonthebasis of evaluation
ofnormalprogrammaterialplayedmonaurallywithamplifiertonecontrols
at the middle,generallyreferred toas "flat!'position.Once the loudspeaker
system has beenbalanced for bestoverallresults,compensation for
additionaldifferences in programmaterialshould be madewith the tone
controls onthe preamplifier or receiver.
Genera'—Generalapplicationnetworkshaveeither a continuouslyvariable
orthreepositioncontrol.With the control inthemid position,evaluate the
relativeloudness of highfrequencyprogrammaterial and raise or lower
thecontrolsetting to obtain the mostrealisticmusicalbalance.When two
dividingnetworks are required,suchasanN8000usedinconjunctionwith
anLX13.first setthe highfrequencynetworkcontrol atits minimum
position(sothe ear willperceiveonly the balancebetween thelow
frequencyandmidrangecomponents),secondly,adjust thelow frequency
network for themostpleasingbalance,andfinally,adjustthehighfrequency
network forthe mostpleasingtrebleperformance.
13

LX30 and LX300-Vne LX30andLX300havePresence(midrange)and
Brilliance(highfrequency)controls.RotatetheBrilliancecontroltothe
minimum position, adjustthePresence control, andthensettheBrilliance
control.
Mounting Generalapplicationdividingnetworksareusuallymountedon
therearpaneloftheenclosure.Thecutoutpatternillustratedislorself-
containednetworksandforthecontrolassemblyofthelargerLX30.LX50A
andLX80A.Woodscrews,aswellasmachinescrewsandT-nuls,arepro-
videdtosecuretheassemblytotheenclosure.Becertainthatthewhite
vinylflangegasketisinplaceinordertomaintainanairtight seal. Themain
assemblyofthelargernetworksisnormallyplacedononeoftheinterior
surfacesoftheenclosureandsecuredbyfourmachinescrewsextending
throughthepanelintothreadedfastenersonthenetwork.
LX30. LX50AandLX80A
203mm
8n
U3rr.m
554in
Himm
4Sin Gin
LX300
6'/.in
111 mrn_
NetworkMountingDimensions

NetworkConnection Thenetworkinputterminalsshouldbeconnected
totheamplifierloudspeakeroutputs.Connecttheblackterminalotgeneral
applicationnetworkstothenegativeamplifieroutput,andtheredterminal
tothepositiveamplifieroutputHeavy-dutynetworksareprovidedwith
screwterminalsTheinputterminallocatedonthewhiteline,marked"C"
lorcommon,shouldbeconnectedtothenegativeamplifieroutput;
connecttheotherinputterminaltothepositiveamplifieroutput.
Generalapplicationnetworkshaveeyeletsthaiallowleadwirestopass
throughtheflangeintotheenclosureandatthesametimemaintainan
airtight seal. TheLX30,however,hasscrewterminalsonthebackofthe
controlassembly.Color-codedwiresareprovided,althoughany18-gauge
insulatedwirecanbesubstituted.Theproperwiregaugefortheamplilier
connectionisdiscussedunderAmplifierConnection
Connectionsbetweenthenetworkandthecomponentsareillustrated
intheaccompanyingdiagrams,asindicatedintheNetworkSelection
ChartCareshouldbetakentofollowthediagramsexactlytoensurethat
componentswilloperalointheproperphaserelationshipwitheachother.
Notethathighfrequencycompressiondriverphasingisa function of the
crossoverfrequencyaswellasthehorn/lensassembly utilized. Thewiring
illustrationsarecorrectwhenanHI.87.HL91.HL92 or HL93ismountedon
theenclosurebafflepanel,andwhenanHL88.HL89orI1L90ispositioned
sothatthehornmouthisflush(even]withtheenclosurebafflepanel. If the
horn/lensassemblyismovedmorethansixinchestoward or awayfrom
thelistener(withrespecttothemountingconditionsjustoutlined),install a
phasereversingswitchfdoscribedonpage24) andauditionmalevocal
materialwhilechangingphaseofthehighfrequencydriver.Utilizethephase
conditionwhichyieldsthemostnaturalreproduction.
Network Selection Chart
Network
Low
frequency
Transducers
Midand High
Frequency Horn/t
ons
Assembly
Illus-
tration
LX5 LEI5H
376'
HL93
A 0
LXIO LE14H LE175.LE85 IIL87 HL9I D
LXI3 LE15H LE175,LE85 HL92 A
1X14 LEIOH LFPIH
C
LX30 124H.LEI4H LE5H+077
I
LX50A 130H, I36H
376'
HL88HL89.HL90 F
LX80A
124H.130H.136H
LE14H LE175.LE8S.376
HL92. HL93 F.G
1X200R I24H. !36H.Lbl4H IE175.LE85
IIL91
K
LX300 124H.136H.LEI4H
LE 175+077
LE85+ 077
HL9? L
N1200 DI30H. I30H LE175.LE85 HL87.HL91 H
N2400 Q130H 075 1
N7000 376+075
376+077
J
N8000 LE175+
075
LE175+Q77
LE85+075
LE85 '077
J
'S'vaiine a/6sapi!i-ar90CC''"pftt*^oofl''VC*"-8P M7000 wft anO/Sof 077 *r.J im wquirM ?ar extended *vg*
'roarer*:/ rep'od.xi on
•Whirl tre 376 is JSSO «*nt*e LXWA connectThe N'OCO ai -f i «ere <N» compfett'en flavor shown m lustrate f
Cc^ecW-s W«l meN7CC0 to re 376 and 075 cr 377 g-e snown i kn fate" J
15

A
System Wiring Illustrations
NoieThecolorcodesillustratedrepresentthelatestconfiguration.Earlierunitswere
suppliedwithIwoblackwiresinsteadotgreen/blackandyellow/blackwires,anda
redwireinsteadofIheyollowwireshown.

c
NoieThecolorcodesillustratedrepresentthelatestconfigurationEarlierunitswere
suppliedwithtwoblackwiresinsteadolgreen/blackandyeilow/Wackwires,anda
redwireinsteadolIneyellowwireshown.

18
Noto: Thecolorcodesillustratedrepresentthelatestconfiguration.Earlierunitswore
suppliedwithtwoblackwiresinsteadotgreen/blackandyellow/blackwires,anda
redwireinsteadoftheyellowwireshown.