Dynaudio Air Series manual Absorbers, Diffusers, Membrane absorbers, Porous absorbers

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ACOUSTICS - BACKGROUND INFO

Absorbers

All materials in the room act acoustically even if they are not so-called acoustical materials. Basically we have three kinds of absorbers.

Membrane absorbers

This kind of absorber includes wooden floors, windows, doors, etc. This absorber provides absorption in the low end of the frequency range. The efficiency is normally not very high, but under normal conditions large areas are included in the basic room construction. Special designed membrane absorbers can be very effective.

Diffusers

A diffuser provides diffuse reflection of the sound radiated against it. It can be a very useful solution in cases where reflections are disturbing the sound image and it is not advisory to ad further absorption. So in order to reduce flutter echoes, comb filtering etc., special elements can be placed on the "disturbing" surface. These elements must have dimensions comparable to the frequencies at which diffusion is wanted.

Absorbtion or diffusion ?

Resonance absorbers

Resonance absorbers include slit panels, perforated plate, Helmholtz resonators etc. These absorbers are normally used in the frequency midrange. The absorption is medium to high.

Porous absorbers

These absorbers include mineral wool, carpets, curtains, and so on. They can be very effective, but the thickness of the material has to be taken into account. Thin layers will only absorb the highest frequencies. (Think of a rehearsal room in the concrete basement where the only damping is a carpet on the floor: Not good at low frequencies!)

To absorb a given frequency (and all frequencies above) the thickness of the absorber must be the quarter of the wavelength of that frequency. Or: the front of the material must be placed at a distance of one quarter of the wavelength.

A special technique developed by Manfred Schroeder is very capable in making a smooth and controlled diffusion. These diffusers normally referred to as "Schroeder Diffusers" can be found as prefab modules.

 

 

 

 

 

 

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Cross section of one example of the Schroeder Panel.

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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 DisplayStereo Setup with mono Subs SetupsStereo Setup Stereo Setup with stereo SubsThis illustration shows how to connect a 5.1 digital setup Digital SetupAnalog 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 MasterAnalog/Digital setup Stereo Setup With Chains on L & ROther Chained Setups Analog connectionsDigital 192 kHz Digital Setup Break IntroductionThis Manual Product ConceptMaster Unit Remote ControlCommon Features Slave & Sub UnitsSlave/Sub Rear Panel Description MasterMaster Unit Analog I/O Optional Digital I/O cardEnter key Cursor UP/DOWN keys AIR DisplayOverload Indication Overload Indication LEDBasic operation in all menus Press Enter to access the Select ModeParameter Description Main DisplaySet Monitor Task Setup MenuSetup External ClockRecall LFE channel noteStore Placing the Monitors OverviewOn the bridge / Console Close to wall / WallOther situations Checking by ear when listening to the signals In phase Checking the placementPhase checking EvaluationEqualizing NextAcoustic level calibration Calibrating Main Monitors CurvesInterchannel calibration CurvePlacing the Subwoofer Low frequency sweeps EvaluationControlling standing waves Checking summing phase cancellationTo Calibrate Checking the CrosspointLFE Gain PhasePhase Introduction PolarityGood acoustics AcousticsReverberation time Sabines formula Membrane absorbers AbsorbersDiffusers 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 SubwooferCross-overs Subwoofer & LFE Channel Background InfoLFE Channel 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 REF Level 1-3 keys Preset 1/3 and 2/4 keysVolume potentiometer Shift keyAIR Soft Navigating AIR SoftMain ToolsPreset List NetworkSystem Setup Calibrate AIR-Base Chained monitorsGlobal Parameters Reset ProceduresMiscellaneous Local ParametersAES/EBU Standard cables CablesTC Link Standard Cat-5 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