NHT A-20 Owner's manual
- Category
- Supplementary music equipment
- Type
- Owner's manual
This manual is also suitable for
NHT A-20 is a studio monitor system comprising a dedicated control amplifier and loudspeaker monitor cabinets with controlled impedance cables that contribute to the crossover network. It's an exceptional product for audio production, enabling transparent and accurate assessment of sound for critical tasks like microphone placement, EQ adjustment, and mix balancing.
NHT A-20 is a studio monitor system comprising a dedicated control amplifier and loudspeaker monitor cabinets with controlled impedance cables that contribute to the crossover network. It's an exceptional product for audio production, enabling transparent and accurate assessment of sound for critical tasks like microphone placement, EQ adjustment, and mix balancing.
Copyright2001NHTPro,aRecotonCorporationBrand
A-20
OwnersManual
A-20LeftMonitorSerialNumber:
A-20RightMonitorSerialNumber:
A-20ControlAmplifierSerialNumber:
CAUTION
RISKOFELECTRICSHOCK
DONOTOPEN
WARNING:SHOCKHAZARD-DONOTOPEN.
AVIS:RISQUEDUCHOCELECTRONIQUE-
NEPASOUVRIR.
SafetyInstructions--PleaseReadFirst
DETAILEDSAFETYINSTRUCTIONS:
Allthesafetyandoperationinstructionsshouldbereadbeforetheapplianceisoperated.
RetainInstructions:
Thesafetyandoperatinginstructionsshouldberetainedforfuturereference.
HeedWarnings:
Allwarningsontheapplianceandintheoperatinginstructionsshouldbeadheredto.
FollowInstructions:
Alloperationanduserinstructionsshouldbefollowed.
WaterandMoisture:
Theapplianceshouldnotbeusednearwater(e.g.nearabathtub,washbowl,kitchensink.laundrytub,inawetbasement,ornearaswimming
pooletc.).
Ventilation:
Theapplianceshouldbesituatedsothatitslocationorpositiondoesnotinterferewithitsproperventilation.Forexample,theappliance
shouldnotbesituatedonabed,sofa,rug,orsimilarsurfacethatmayblocktheventilationopenings,orplacedinabuilt-ininstallation,such
asabookcaseorcabinetthatmayimpedetheflowofairthroughtheventilationopenings.
Heat:
Theapplianceshouldbesituatedawayfromheatsourcessuchasradiators,heatregisters,stoves,orotherappliances(includingother
amplifiers)thatproduceheat.
PowerSource:
Theapplianceshouldonlybeconnectedtoapowersupplyofthetypedescribedintheoperatinginstructionsorasmarkedonthe
appliance.
GroundingandPolarization:
Precautionsshouldbetakensothatthegroundingorthepolarizationmeansoftheapplianceisnotdefeated.
PowerCordProtection:
Powersupplycordsshouldberoutedsothattheyarenotlikelytobewalkedonorpinchedbyitemsplaceduponoragainst them,
payingparticularattentiontocordsandplugs,conveniencereceptaclesandthepointwheretheyexitfromtheappliance.
Cleaning:
Theapplianceshouldonlybecleanedasrecommendedbythemanufacturer.
Non-usePeriods:
Thepowercordoftheapplianceshouldbeunpluggedfromtheoutletwhenleftunusedforalongperiodoftime.
ObjectandLiquidEntry:
Careshouldbetakensothatobjectsdonotfallandliquidsarenotspilledintotheenclosurethroughopenings.
DamageRequiringService:
Theapplianceshouldbeservicedbyqualifiedservicepersonnelwhen;
Thepowersupplycordortheplughasbeendamaged;or
Objectshavefallen,orliquidhasbeenspilledintotheappliance;or
Theappliancehasbeenexposedtorain;or
Theappliancedoesnotappeartooperatenormallyorexhibits amarkedchangeinperformance;or
Theappliancehasbeendropped,ortheenclosuredamaged.
Servicing:
TheusershouldnotattempttoservicetheappliancebeyondwhatisdescribedintheOperatingInstructions.Allotherservicing
shouldbereferredtoqualifiedservicepersonnel.
CAUTION:Toreducetheriskofelectricshock,donot
removethecover(orback).Nouserserviceablepartsare
inside;referservicingtoqualifiedpersonnel.
WARNING:Toreducetheriskoffireorelectricshock,do
notexposethisappliancetorainormoisture.
Thissymbolwhereveritappears,alertsyoutothe
presenceofuninsulateddangerousvoltageinsidethe
enclosurethatmaybesufficienttoconstituteariskof
electricshock.
Thissymbol,whereveritappearsalertsyouto
importantoperatingandmaintenanceinstructionsin
theaccompanyingliterature.Readthemanual.
RackRail
A-20
Amplifier
FrontPanel
Screws
Insulating
Washers
Fig.1:RackMountingDetail
INTRODUCTION:
ThankyouforyourselectionoftheA-20.Yourstudiomonitorsareacriticalelementinthecountless
decisionsmadeduringrecording,mixing,masteringandotherkeyaspectsofaudioproduction.They
mustdeliveratransparent,neutralandrevealingassessmentofsound,sothatyouhavethe
informationyouneedtochooseandplacemicrophones,setEq’s,balancemixes...Inotherwords,deliver
exceptionalproduct.TheA-20iscapableofstateoftheartsonicresolutionandflexibility.Investing
timetolearnabouttheA-20’sfeaturesandoperationwillrewardyouwith thebestpossible
performance.
Ifyourequireassistanceatanytimeduringorafterthesetupprocess,callourCustomerServiceHotLine
at(800)-NHT-9993(648-9993).Youcanalsovisitourwebsiteatwww.nhtpro.comformoreindepth
technicalinformation.Thanksagainforyourconfidenceinourproducts!
GETTINGSTARTED:
TheA-20isuniqueinthatitcombinesadedicatedcontrolamplifierwithloudspeakermonitorcabinets,using
controlledimpedancecablesthatactuallyformpartofthecrossovernetwork.Bydesigningthesystem
asanintegralpackageinthismanner,manyoftheadvantagesofself-poweredspeakerscanberealized
withoutattendantperformancecompromises.However,itmustberecognizedthatthecontrolamp,cablesand
monitorsareaninseparablepackage.
ThefollowingareincludedintheControlAmplifiercarton:
1ea.-ControlAmplifier2ea.-20'MonitorOutputCables
1ea.-6'IECPowerCord4ea.-10-32RackMountingScrews
1ea.-WarrantyRegistrationCard8ea.-PlasticInsulatingWashers
Note:TheA-20mustonlybeusedwiththeA-20ControlAmp,cables,andviceversa!.
TheA-20ControlAmplifiermaybeusedonashelf,ormountedinastandard19”equipmentrackusingthe
screwsandwasherssupplied.Forrackmounting,removeandretainthefourfeetfromthebottomoftheamp
chassisusinga#2Philipsscrewdriver.Twoverticalrackspacesarerequired,butwerecommendyouleave
atleastoneadditionalopenspaceaboveandbelowtheA-20forimprovedcooling,asyouwouldwithany
highpoweramplifier.Fortableorshelfuse,thefourfeetmustremainattachedtoallowforaircirculation.As
astartingpointforspeakerplacement,alignthebackoftheenclosuresparalleltotherearwall,withtheangled
frontsfacingintowardsyou.Formoredetailedspeakerplacementinformationseepage7.
Fig.2TypicalSystemConfiguration
M
POWER
SENSITIVITY BOUNDARY POSITION
+11
+4
-3
-10
FFNF
MF
02
1
SPL TMP VAC
MODE
PHONES
A-20
Control
Amplifier
100
Signalflow
.
ToACLine
Signalflow
Signalflow
MonitorOutputCables
SYSTEMCONNECTIONS:
CAUTION:
CAUTION:
CONTROLAMPLIFIERINPUTSECTION:
SPEAKERCABLECONNECTIONS:
MAKEALLCONNECTIONSWITHTHEACPOWEROFF!
CONNECTINGTHEOUTPUTOFTHEA-20CONTROLAMPLIFIERTO
ANYEQUIPMENTOTHERTHANTHEA-20ORC-20MONITORMAY
CAUSEEQUIPMENTDAMAGE.
TheA-20ControlAmplifieracceptsbothbalancedandunbalancedinputsoneitherXLRor1/4”TRSconnectors.
TheseconnectorsarehardwiredinparallelwithintheA-20toallowforconvenientequipmentchaining,butonlyone
signalsourceshouldbephysicallyconnectedtotheunitatanytime.Figure3ashowstheproperwiringschematicfor
eachtypeofconnector.Sincetherearesomanydifferentconnectortypesandsignallevelsemployedbysource
equipment,someexperimentationmaybenecessary,keepinginmindthattheA-20canacceptawiderange
ofsignalsandhasaninputsensitivitycontrolonthefrontpanel.
TheA-20includestwo20’specialpurposecablestoconnecttheControlamplifiertotheMonitors.Whilethese
cableslooksimilartostandardmicrophonecables,theyareconstructedwithlowerandmoreconsistentconductor
impedance.PortionsoftheA-20’scrossovercircuitryarelocatedinboththeamplifierandspeakerenclosures,and
thecablessuppliedareanimportantpartofthiselectricalnetwork.Thisallowsthespeakercablestofunctionasa
neutralandtransparentcomponentinthesystem.Replacingorextendingthesuppliedcableswithanyothertype
willhaveavarying,andonlypartlypredictableimpactonthesoundoftheA-20.Ifyourinstallationrequirestheuse
ofalternativecables,youmayconsultthetablelistingourmeasurementdataonavarietyofcabletypesat
www.nhtpro.comunderthesupportsection.BesuretheyarewiredasshowninFig.3a.Theseconsiderationsaside,
usingthesuppliedcablestoconnectthecontrolamplifierisquitesimpleandstraightforward.Boththeamplifier
andthemonitorsaremarkedwiththeappropriate“left”and“right”channels.FittheXLRconnectorsintothe
correspondingconnectorsonthecontrolamplifierandmonitorsuntiltheconnectorlocks.
WARNING: IFUSINGCABLESOTHERTHANTHOSESUPPLIEDWITHTHISSYSTEM,
BESURETHATNOCONDUCTIORISWIREDTOTHEXLRCASING.
FAILURETODOSOMAYCONSTITUTEARISKOFELECTRICSHOCK.
Fig.3aBalancedWiringDiagram
1
2
3
+(SIGNAL)
-(GND)
Shield
SOURCE
A-20INPUT
Fig.3bUnbalancedWiringDiagram
NHTPro
MODELA-20CONTROLAMPLIFIER.
SERIALNO:
NHTPro
BENICIA,CALIFORNIA,U.S.A.
A20-A-10001
MADEINTAIWAN G1
CAUTION:
CONNECTINGOUTPUTSTOANY
PRODUCTOTHERTHANA-20or
C-20MONITORSMAYRESULTIN
SEVEREEQUIPMENTDAMAGE.
FUSETYPE:
T9A250VFOR110/120V.
T5A250VFOR220/240V.
50/60Hz-950W
INPUTVOLTAGE
CAUTION
RISKOFELECTRICSHOCK
DONOTOPEN
WARNING:SHOCKHAZARD-DONOTOPEN.
AVIS:RISQUEDUCHOCELECTRONIQUE-
NEPASOUVRIR.
FORCONTINUEDPROTECTIONAGAINST
RISKOFFIREREPLACEONLYWITHSAME
TYPE250VFUSE.
CAUTION:
Fig.4A-20ControlAmplifierRearPanel
USINGTHEA-20CONTROLFUNCTIONS:
POWERINDICATORS:
SYSTEMSTATUSDISPLAY:
SENSITIVITY:
TheA-20controlsaredesignedforutilityandrepeatabilityundervaryingconditions.Youshouldfindtheeffectsofthe
controlssonicallysubtle,withlittleimpactonthebasiccharacterandaccuracyofthespeaker.Weencourage
experimentationtofinetunethesystemtotherequirementsofyourparticularinstallation.
JusttotheleftofthepowerswitchontheA-20ControlAmplifieraretwostatusLED's.Theupper(green)
LEDlightsupindicatingthereisACpowertotheamplifierandthePOWERSWITCHisinthe“on”position.The
lower(red)LEDindicatesaclippingoroverloadcondition.Occasionalflashingofthisindicatorisagentlewarningyou
arereachingthesystem’slimits.IftheredLEDglowscontinually,severeclippingisoccurring.Theinputsignalor
systemgainshouldbereducedtoavoidtheriskofpossiblesystemdamage.
AuniquefeatureoftheA-20ControlAmplifieristheSystemStatusDisplaylocatedinthecenterofthefront
panel.SmallLED’sindicatewhichmodeisbeingdisplayed;greenforaverageSPL,yellowforAClinevoltage,and
blueforheatsinktemperature.Thesquare“Mode”switchtotherightoftheSystemStatusDisplayselects
thedesiredmode.
SPL:Thisisthelongtermaveragesoundpressurelevelcalibratedat2metersfromastereopair,andderived
fromtheamplifieroutputvoltage.Peaksoundlevelsareignored.Thereadoutisdesignedtoinformtheuserof
overalllisteninglevels,andtohelprealizeconsistentmonitoringconditionsfromhourtohour,sessionto
sessionandroomtoroom.Levelsunder68dBareshownas“00”;levelsover120dBareshownas“HI”.
Sincemonitoringlevelhasaprofoundinfluenceontheperceptionofsonics,periodicallycheckingyourlistening
levelshelpstoassureconsistentresults. Makinganefforttocombatlongtermearfatiguecanhelpyouavoid
theheartbreakofharshmorningafterrealities.
VAC:ThisisareadoutoftheACpowerlinevoltagebeingsuppliedtotheA-20.Itisusefulforassuringthat
powerconditionsarecorrectandsufficientforalltheequipmentonthecircuit.Sustainedreadingsbelow110V
maylimityourmaximumoutputlevels,andcouldindicatethattheACcircuitisoverloaded.Continuous
readingsabove125VindicateanACcircuitproblem,whichcouldleadtoamplifierfailure.
TMP:ThisisareadingoftheoutputheatsinktemperatureindegreesCentigrade.Typically,youshouldexpect
thistorunbetween50°Cand80°C,dependingonlisteningandambientconditions.Ifyoufindthatyour
ControlAmplifierunittendstorunhotterthan80°C,itisrecommendedthatyouimprovetheventilationaroundit.
NotethattheA-20ControlAmplifierwillautomaticallyshutdowniftheheatsinktemperaturereaches100°C.
Thiscontrolisusedtochangetheinputsensitivitywithsettingsat;-10dB,-3dB,+4dB,+11dBand(M)uteproviding
noisefree,consistentgainmatchingwithawidevarietyofequipment.Thepropersettingisthelowestsensitivity
possible(highestdBnumber)whichallowsthespeakertoreachthemaximumdesiredoutputwithoutsourceclipping.
Professionaldevicestypicallyspecfulloutputat+4dB,mostconsumeraudioproductsreachfulloutputat-3dB,
andmostcomputersoundcardshaveafullscaleoutputof-10dB.Consulttheowner’smanualforthedevice
connectedtotheControlAmplifierforitsoutputlevelspecificationsandsettheSENSITIVITYcontrol
accordingly.
Fig.5A-20ControlAmplifierFrontPanel
M
POWER
SENSITIVITY
BOUNDARY POSITION
+11
+4
-3
-10
FFNF
MF
02
1
SPL TMPVAC
MODE PHONES
A-20
Control
Amplifier
100
BOUNDARYCONTROL:
Reflectiveboundaries,suchasfloors,walls,eventabletops,reinforceaspeaker’slowfrequencyoutput.
Conversely,placingspeakersoutintoaroomdecreasesbassresponse.Thehighestlowfrequencyoutputiswith
theBOUNDARYcontrolinthe“0”position,whichassumesnosignificantboundaryreinforcementispresent.
Eachcontrolstepattenuateslowfrequenciesby1.5dB(at50Hz),withrapidlydecreasingeffectabove300Hz.
RefertothediagraminFig.6forinformationonsettingthecontrolappropriately.
POSITIONCONTROL:
Near-fieldmonitoringreduces theeffectofroomacousticsonthesignal,andprovidesgreatersonicdetail.Mid-
andfar-fieldlisteningrevealsaspectsofrecordedambienceandismorerepresentativeofenduse.However,a
speaker’supperfrequencypowerresponsechangeswithdistance,duetoroominfluencesandairabsorption.
TheA-20maybeadjustedforflatresponseatvariouslisteningdistances.Themaximumhighfrequencyoutput
isobtainedwiththecontrolinthe“FF”(far-field)position.Eachcontrolstepattenuates20kHzbyan
additional.75dB(towardsthenear-fieldposition)withnoeffectonfrequenciesbelow3kHz.SeeFig.7for
appropriatePOSITIONcontrolsettingsbasedonlisteningdistances.
0
2
1
02
1
02
1
02
1
BOUNDARY
BOUNDARY
BOUNDARY BOUNDARY
BOUNDARY
02
1
QuarterSpace
Quarter/HalfSpace
HalfSpace Half/WholeSpace
WholeSpace
Fig.6.BoundaryControlSettingsDiagram
1M
0’
1.5M 2M
2.5M 3M
Near-field
Mid-field
ListenerDistance
A-20
Monitor
Far-Field
POSITION
FFNF
MF
POSITION
FFNF
MF
POSITION
FFNF
MF
POSITION
FFNF
MF
POSITION
FF
NF
MF
Fig.7.PositionControlSettingsDiagram
SPEAKERPLACEMENT:
SYSTEMOPERATION:
A-20MONITORSYSTEMCARE:
NEEDHELP?
TheA-20MonitorSystemisintendedtoprovideconsistentperformanceoverawiderangeofplacement
situations.Thisisaccomplishedthroughtheuseofelectricalcontrols,widedispersiondrivers,advanced
enclosuredesignandcarefullychosencrossovercharacteristics.Nevertheless,itisalwaysworthinvestingtime
andeffortexperimentingwithoptimumloudspeakerplacement.Inallcases,A-20Monitorsshouldbesetup
symmetricallyequidistantfromthelisteningposition;theleftspeakerandrightspeakershouldbeatthesame
relativepositionswithrespecttotheprimarylisteningarea.Thisisimportantinorderthehearaproperstereo
soundstage.Thespeakerbafflesangleintowardsthelisteningpositionwiththeloudspeakerbacksparallelto
oneanother.AgoodstartingpointcanbefoundinFigure8below.Ideally,thetweeterheightshouldbeon
axiswithyourears,orslightlyabove.Also,rememberthatnearbyreflectivesurfacescanalterimpulse
response,blurimagingandchangetonality.
TheA-20iscapableofveryhighoutputlevels,especiallywhenlisteninginthenear-field.Protectyourearsanduse
commonsense.Still,everyspeakersystemhasitslimits.Harshbreakupatextremelyhighvolume,orheat
emanatingfromthedriversisanindicationthatthesystemhasexceededitsoutputlimitsandyoushouldlowerthe
playbacklevel.WatchforexcessivelightingofthefrontpaneloverloadindicatorontheControlAmplifier.Speaker
damagemostoftenoccursfromsustainedhighvolumelevels,notfromtransientsoundsorbriefmusicalpeaks.
Exceptfortheoccasionalflatteringcomment,yourA-20Systemneedsnoregularmaintenance.Neverattemptto
cleantheA-20monitordriverunitsexceptforverylightfeatherdusting.TheA-20monitorcabinetsandtheA-20
ControlAmplifierfrontpanelcanbecleanedusingadamp,softcottonclothfirstsprayedwithamild,non-abrasive
glasscleaner.Neverspraythespeakeroramplifierdirectly!Avoidsiliconeandoilbasedcleanersortreatments.
TechnicalSupportcanbereachedseveralways:Telephoneus(800)-NHT-9993(648-9993),E-mailusat:
[email protected],Faxusat:(707)748-5945orwriteusat:NHTPro,527StoneRd.,Benicia,CA94510.Orvisit
ourworldwidewebsiteatwww.nhtpro.com.
ListeningPosition
D
Fig.8IdealMonitorPlacement
SYSTEMSPECIFICATIONS:
PERFORMANCESPECIFICATIONS:
FEATURES/CONTROLS:
Type:Modular,two-piecepowerednear/mid/farfieldmonitor.
Configuration:2-wayacousticsuspension.
Woofer:6.5"curvilineartreatedpaper.Butylsurround.
Tweeter:1"metaldome,textilesurround,ferrofluidcooledanddamped.
MagneticShielding:Partial,12-18”workingdistancefromPCmonitorrecommended.
AmplifierPower:250W(continuousRMS/ch),400W(100mspeak).
PeakAcousticOutput:117dBSPL(100mspinknoise@1M).
Residualhum/noise:<10dBSPL@1M.
SystemTHD@90dBSPL:<0.4%(100Hz~10kHz@1M).
Response+/-2dB:48Hz~20kHz@1M,45Hz~20kHz@2M(1/3oct.sweptnoise)
-6dBLFcutoff:40Hz(in-roomresponse).
LoudspeakerDim./Wgt.:14"hx7.5"wx11.9"d,19lbs.
LoudspeakerMaterials:0.75"MDFw/highpressurelaminate(internal+external).
ControlAmp.Dim./Wgt.:3.5"hx19"wx13.375"d/37lbs.
Connectors:Input:XLR,TRS.
Outputtomonitor:XLR.
Controls:Sensitivity:5position(-10dB,-3dB,+4dB,+11dB,Mute).
Boundary:5position(0.0,0.5,1.0,1.5,2.0representingwalls).
Position:5position,near(1M),near-mid(1.5M),mid(2M),mid-far(2.5M),far
(3M~).
Power:On,off.
Display:Switchable:SPLOutput(68dB~120dB),LineVoltage(90~135VAC),HeatSink
Temp.(20-99C).
LED’s:Power,Overload.
Other:HeadphoneOutput(insertioninterruptsmainoutput).
o
NHTPro
527StoneRd.
Benicia,CA94510
ph:(707)748-5940
fx:(707)748-5945
www.nhtpro.com
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NHT A-20 Owner's manual
- Category
- Supplementary music equipment
- Type
- Owner's manual
- This manual is also suitable for
NHT A-20 is a studio monitor system comprising a dedicated control amplifier and loudspeaker monitor cabinets with controlled impedance cables that contribute to the crossover network. It's an exceptional product for audio production, enabling transparent and accurate assessment of sound for critical tasks like microphone placement, EQ adjustment, and mix balancing.
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