PROEL DSO480 - Crossover Filter Slopes; Time Alignment

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Notethat,forsafety,alwayssetthelimiterthreshold1or2dBbelowthemaximumallowableworkedout
usingtheabovemethod.
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ALWAYSREFERTOYOURSPEAKERMANUFACTURERFORLIMITERSETTINGS.
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CrossoverFilterSlopes
Itshouldalsobenotedthattheturnoverfrequencydisplayedonthescreenisthe‐3dBpointforalltypes
exceptLinkwitz‐Rileywherethe‐6dBpointisshown.Ifthe‐6dBpointistobeusedfortheBesselor
Butterworthfilter,taketherequiredcrossoverfrequency,multi
plythisbytheappropriatefactorfromthe
followingtableandthenselecttheclosestavailablefrequencyonthedisplay.
Filter Type High pass factors Low pass factors
Bessel 12 dB/Oct. 1.45 0.69
Butterworth 12 dB/Oct. 1.31 0.76
Bessel 18 dB/Oct. 1.37 0.73
Butterworth 18 dB/Oct. 1.19 0.84
Bessel 24 dB/Oct. 1.35 0.74
Butterworth 24 dB/Oct. 1.15 0.87
Bessel 48 dB/Oct. 1.39 0.72
Butterworth 48 dB/Oct. 1.08 0.93
Pleasenotethatunlikeconventionalanaloguecrossovers,crossoverpointsandslopesaresetwithabsolute
accuracysincecomponenttoleranceproblemsdonotoccur.
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Pleaseseepage18fordetailsofhowtoadjustthehighandlowpasscrossoverfiltersettings.
TimeAlignment
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AfurtheradvantageoftheDSO480 overconventional productsistheprovisionofanindependentlyadjustable
delaysectionforeachoutput.Thisallowsthetruearrivaltimefrommultipledriverstopreciselyalignedrather
thanrelyingonthecompromise'phaseadjust'approach.Delaytimeisadjustablein0.3µSsteps(0.1m
m).
Pleaseseepage17fordetailsofhowtoadjustthedelaytimes.
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Toconvertfromunitsoftime(i.e.milliseconds)tounitsofdistanceusethefollowingformula:
1millisecond=343mm(1.126ft)@20°C(68°F)
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Tocalculatetimedelayforaknowndistance,use:
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Timedelay= Distanceinmet
ers
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20.06x√273+°C
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where°Cisthetemperaturein°C.
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Tosimplifythisequationat20°C.
Delaytimeinmilliseconds=
(Distanceinmetersx2.192)or(Distanceinfeetx0.955)
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Note:Centigrade=(Fahrenheit–32)x0.5555.