Dynaudio Air Series manual Or +, Dip frequencies

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ACOUSTICS - BACKGROUND INFO

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Two typical situations in which comb filters arise, either acoustically or electrically.

In general: All digital signal processing takes time. This means in practice that comb filter effects can arise if you loop a signal via, for example, a compressor and combine this signal with the original.

An example of a comb filter created by the combining of two signals with the same amplitude, but with a time delay between them of just 1 ms.

It can be seen that a dip occurs due to cancellation at 500 Hz, 1.5 kHz, 2.5 kHz, etc.

It can also be seen that the two signals add to double their value (+6 dB) at low frequencies and with a full wavelength's delay at 1 kHz, 2 kHz, 3 kHz etc.

Dip frequencies

Cancellation occurs for a comb filter at all the frequencies where the two signals are in opposite phase. This occurs when the time delay comprises duration of ½, 1½, 2½, etc. periods. At 1 kHz the period is 1 ms. Half of the period is 0.5 ms.

If a time delay of precisely 0.5 ms occurs, it means that cancellation will arise, not just at 1 kHz, but also at 2 kHz, 3 kHz, 4 kHz etc.

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Contents Page Page Important Safety Instructions Voltage Line plug according to standardPage Table of Contents Quick Setup Reference Quick Setup Reference Operational Overview Main DisplaySetups Stereo SetupStereo Setup with mono Subs Stereo Setup with stereo SubsDigital Setup Analog SetupThis illustration shows how to connect a 5.1 digital setup This illustration shows how to connect a 5.1 analog setupThis illustration shows how to connect a 5.3 Digital setup This illustration shows how to connect a 5.3 Analog setupThis illustration shows how to connect a 6.1 Analog setup Dig/6 MasterStereo Setup With Chains on L & R Other Chained SetupsAnalog/Digital setup Analog connectionsDigital 192 kHz Digital Setup Introduction This ManualBreak Product ConceptRemote Control Common FeaturesMaster Unit Slave & Sub UnitsRear Panel Description Master Master Unit Analog I/OSlave/Sub Optional Digital I/O cardAIR Display Overload IndicationEnter key Cursor UP/DOWN keys Overload Indication LEDPress Enter to access the Select Mode Parameter DescriptionBasic operation in all menus Main DisplaySetup Menu SetupSet Monitor Task External ClockRecall LFE channel noteStore Placing the Monitors OverviewOn the bridge / Console Close to wall / WallOther situations Checking the placement Phase checkingChecking by ear when listening to the signals In phase EvaluationEqualizing NextCalibrating Main Monitors Curves Interchannel calibrationAcoustic level calibration CurvePlacing the Subwoofer Low frequency sweeps EvaluationChecking summing phase cancellation To CalibrateControlling standing waves Checking the CrosspointPhase Phase IntroductionLFE Gain PolarityGood acoustics AcousticsReverberation time Sabines formula Absorbers DiffusersMembrane absorbers Absorbtion or diffusion ? Resonance absorbersBackground Info Acoustics Standing WavesRoom modes Axial Tangential RadialHow to prohibit standing waves How does the standing waves influence the sound field?Acoustics Background Info Comb Filtering Or + Dip frequenciesRear wall cancellation Subwoofer Background Info SubwooferSubwoofer & LFE Channel Background Info LFE ChannelCross-overs Low Pass LFE GainAcoustic summation of audio signals Delaying Monitors LINE-UP & CalibrationCinema setup LINE-UP & Calibration Background Info How to measure the sound pressure?Calibration of 5.1 in an ITU-775 arrangement AIR Remote Remote Control FeaturesIntroduction Preset 1/3 and 2/4 keys Volume potentiometerREF Level 1-3 keys Shift keyAIR Soft Navigating AIR SoftMain ToolsPreset List NetworkSystem Setup Calibrate AIR-Base Chained monitorsReset Procedures MiscellaneousGlobal Parameters Local ParametersCables TC Link Standard Cat-5 cablesAES/EBU Standard cables Serial to Cat-5 cableAIR 6 & AIR 15 Master and Slave AIR 20 & AIR 25 Master and SlaveAIR-Base-1 & AIR-Base-2 AIR BaseGeneral for all Products Room & DistanceAIR Remote specs Delay in System & Error Messages ETC Error messages etcCertificate Of Conformity Certificate of ConformityAIR AIR-Base Preset List # Name