Page8 ReferenceManual
thesystemtobetunedtoaflatresponse.Morelaborious,butatleastasaccurate,wouldbeto
plottheresponsecurveusingasweepableSWO.BothrequireaRPM.
TheRTAandSWOmethodsinvolvemutingallbutonebandononeside,firingpinknoiseor
theappropriate(X-over)frequencythroughthesystematacomfortablelevel,andobserving
theSPLattheRPM.Switchonanadjacentband.ThemeasuredSPLattheRPMshould
increaseby+3dBatthecrossoverpoint.Repeatforallcrossoverpoints.
Doublecheckbylookingattheentireaudiospectrum.Inahall,thefrequencyresponseofthe
systemwill becolored(whichiswhymassivesystemsaresometimescalibratedoutdoors).
Whatyouwillbelookingforisnotatrueflatresponse:thatwillonlycomeafterequalization.
Ratherseekoutfaultlinesbetweenbands.Ifthefrequencyresponseisverycurvedindeed,
however,itmightbebettertousethecrossovertoflattentheroombeforeapplyingEQ.Inthis
case,faultlinesmightjusthavetobeacceptedandcompensatedforasbestyoucanwith
systemEQ.
Extremelystablehigh-gualitypotentiometersobviatetheneedforfixedcardfrequency
dividersofferingadegreeofon-siteusercontrolnotfoundoncertainmoreexpensiveunits.
Theseoperateintwoswitchableranges,from80-900Hz,andfrom800Hz-9kHz.Turnover
frequenciesbeyondthoselimitsarenevernormallyrequired.Theslopeis24dB/octave.And
thefiltersaretheuniversallyacclaimedlinkwitz-Rileytype.Highqualitycomponents(1%metal
filmresistorsand2%capacitors)ensurezerophaseandamplitudeerroratallcrossover
frequencies.
Forsettingcrossoverfrequenciesbetweenbins&hornsetc.,pleaserefertothe
manufacturer'sspecifications.Ifpossible,checkresponsecurvesofthevariousloadeddrivers
(i.e.incabinets/behindhorns)toavoidcrossingoveratapeakortrough.Lookinsteadfor
relativelyflatmatchingareas.
Neverdriveloudspeakers/hornsatfrequenciesbellowthemanufacturer'sspecifiedbandwidth.
TIP:Crossingoverabovearecommendedfrequencyoftenputslesssfressonahorndriveror
tweeter,resultinginalongerdiaphragmlifeandclarity,versusaslightdropinsystemefficiency.
CertainPAsystems,particularlythoserequiredtodeliverloud,deepbass,runthelowendin
mono,whilethehighsareinstereo(lowfrequencysoundishardtolocalize).Byplacingall
basscabsinanarray(theclosertoaspherethebetter,inpracticetwomaybeontopoftwo
others),efficiencyisimprovedoverallotherstackingmethods.E.g.twocabstogetherwill
provide+3dBmore(doublethevolume)oflowbassthanthesametwoseparatedbyastage.
Fourcabstogetherprovideanextra+6dB.Why?Togethertheyformasinglesource.Apart
theyarediscretesources.Thesphericalnatureofbasswavesmeansthatapartthereisbound
tobesomephasecancellationinthemiddle.Trydroppingtwostonesintoapondtogetherand
apartinyourmind'seye.Gotthepicture?Instereomodethecandelivermonobass
viatheswitchcalledMONOBASS.
Also,manystudionearfieldmonitorsnowcomewithoptionalmonosub-woofersystems.In
stereomodethecandeliveramonosignalsuitablefordrivingsuchasub-wooferor
SPLAtRPM
SeekingOutFaultLines
WCR35
WCR35
SETTINGCROSSOVERFREQUENCIES
MONO-INGTHEBASS