Dolby Laboratories DP570 A.3.7 Measuring SPL, A.3.8 Computing Channel Trims , A.3.9 Subwoofer Calibration

Configuring a Monitor System Calibrating Speaker Playback Levels
Dolby® DP570 Multichannel Audio Tool User’s Manual 69
A.3.7 Measuring SPL
ToaccuratelymeasureSPL:
1. Sitinthereferencelisteningposition.SettheSPLmetertoCweightingandSlow
response.
2. Facingthefrontspeakers,holdtheSPLmeteratchestlevel,withthemicrophone
facingupatanangleofapproximately45degreestotheCenterspeaker.Keepthe
meteratarm’slengthtopreventmeasuringaudiothatmayreflectfromyourbody.
3. KeeptheSPLmeterinthisposition.MakesurethatthemeterisaimedattheCenter
speakerasyoutakereadingsfortheLeftandRightspeakers.
4. TotaketheSPLreadingsfortheLeftSurroundorRightSurroundspeakers,keepthe
meteratthesameangleandpositionasyoudidforthefrontspeakers.Turnyour 
body90degreesfromtheCenterspeakertowardthewallclosesttotheSurround
speakeryouaremeasuring.Thisminimizesshadowing(obscuringthemeterwith
yourbody).
A.3.8 Computing Channel Trims
Aftermeasuringeachspeaker,computethedifferencebetweenthemeasuredactualSPL
andthetargetSPL.AdjustthetrimforeachspeakerappropriatelyusingtheMultichannel
Trims controlsshowninFigure A‐8.
Figure A-8 Multichannel Trims Controls
Whenyouhavesettrimlevelsforallyourspeakers,clickthetestnoisecontrolshownin
Figure A‐2directlyundertheAnalogOutputscheckbox.
A.3.9 Subwoofer Calibration
Subwoofersarecalibratedusingadifferentprocessthantherestofthespeakers,preferably
withdifferentequipment.Toproperlycalibratethesubwoofer,areal‐timeanalyzer(RTA)
isrequired.IfanRTAisnotavailable,youcanapproximatethesettingswithanSPLmeter.
WhenusinganRTA,propercalibrationrequiressettingtheLFEchannelsignalsenttothe
subwoofer,withinitstypicalbandwidthof25to120Hz,10dBhigherthanthemain
channels.FigureA‐9showsasampleRTAdisplayofaproperlycalibratedsubwoofer.