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21. február 2005 1 Elektroakustika Šk.r. 2004/2005 Cvičenie doc. Ing. Jozef Juhár, PhD. tuke. sk.

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Presentation on theme: "21. február 2005 1 Elektroakustika Šk.r. 2004/2005 Cvičenie doc. Ing. Jozef Juhár, PhD. tuke. sk."— Presentation transcript:

1 21. február 2005 1 Elektroakustika Šk.r. 2004/2005 Cvičenie doc. Ing. Jozef Juhár, PhD. http://voice.kemt.fei. tuke. sk

2 21. február 2005 2 Elektroakustický systém (časť reprodukcie)

3 21. február 2005 3 Bassunit

4 21. február 2005 4 implementuje zjednodušený model elektrodynamického reproduktora v zatvorenej alebo basreflexovej ozvučnici je určený na predbežnú simuláciu reproduktorovej sústavy rovnakú reproduktorovú sústavu možno simulovať neskôr rozdelením na prvky Driver-, Enclosure- and Radiator Hornopriepustný filter 2. rádu – elektrický... An electrical high-pass filter connected before the loudspeaker can substantially improve reproduction characteristics and the load capacity of the bass loudspeaker. The filter limits the excursion of the diaphragm. The model used in the Def_Bassunit element is relatively simple and allows a mathematically closed description. It is therefore an obvious step to specify the required high-pass filter at the same time. The dialog forming part of Def_Bassunit element supports high- pass filtered system and also calculates the performance data.

5 21. február 2005 5 BassUnitKeyword '...'Identifier. Def='...'Reference to the associated definition Def_BassUnit. Node=s=tThe connection terminals of the driver are between poles s and t. The phase position of the radiated sound is inverted if the poles s and t are exchanged. x=...m y=...m z=...mMounting position of diaphragm center. HAngle=...° VAngle=...°Mounting angles. Povinné parametre

6 21. február 2005 6 t1=...mDisplacement of diaphragm within baffle.. WEdge=...m HEdge=...mDiffraction. Width and height of baffle. Must be given if the keyword Reflection is used. ReflectionIf specified radiation is modified by reflections (see Def_Reflector). NoRadNo radiation takes place. NoDirRadiates as a point source. Note If Def_Bassunit, the definition forming part of the Bassunit element, describes a driver in the reflex enclosure, the entry for the position of the reflex vent is missing here. The reason is that the simplified model of Def_Bassunit uses the velocity of sound in the enclosure as output parameter, which - as can be demonstrated - is equal to the sum of the radiation of diaphragm and vent (within the scope of the simplified model). If the tunnel, measured at the wavelength, is distant from the diaphragm or if more accurate analyses are to be carried out, then the reflex enclosure is built up from the Driver, Enclosure and Radiator. Nepovinné parametre

7 21. február 2005 7 Def_BassUnitKeyword '...'Identifier of definition. fs=...HzResonance frequency. Vas=...m3Equiv. volume of compliance to diaphragm suspension. Mms=...kgMass of diaphragm assembly. Cms=...m/NCompliance of suspension. Qms=...Mechanical quality factor of free radiating driver. Rms=...Ns/mMechanical Resistance. Qes=...Electrical quality factor of free radiating driver. Bl=...TmConversion factor. Re=...ohmResistance of voice coil. dD=...mDiameter of driver diaphragm. SD=...m2Area of circular diaphragm. WD=...m HD=...mWidth and height of rectangular diaphragm. Vb=...m3Volume of enclosure. Def_Bassunit: Povinné parametre

8 21. február 2005 8 fre=...HzMakes Re frequency dependent to simulate the influence of eddy currents at high frequencies. ExpoRe=...Controles the resistance of the voice coil. Le=...HInductivity factor of voice coil. ExpoLe=...Controles the reactance of the voice coil. dD1=...mDiameter of inner diaphragm. SD1=...m2Area of inner diaphragm. tD1=...mDepth and height of cone and dome diaphragms, respectively. t1=...mDisplacement of diaphragm within baffle. fp=...HzMass reduction frequency of cone and/dome dome diaphragms Diffuse=...%Directivity control factor Xms=...mMaximum linear diaphragm excursion of driver. Rg=...ohmGenerator resistance. mb=...Mass load factor. fb=...HzHelmholtz-resonance. If given, Def_Bassunit simulates a reflex- enclosure. Qb/fo=...Enclosure quality factor. Qe=...Quality factor of high pass filter. fe=...HzPole-frequency of high pass filter Def_Bassunit: Voliteľné parametre

9 21. február 2005 9 Driver

10 21. február 2005 10 Network element Electroacoustic network-driver. The parameters are described in the associated definitions Def_Driver, Def_TwoCoilsDriver, Def_PiezoDriver. If the Driver network element refers to the Def_Driver or Def_PiezoDriver definition, then the Driver element is a four pole driver. If, on the other hand, it refers to the Def_TwoCoilsDriver definition, then the driver is six-poled. The input poles s and t are in the electrical part of the network, the current flowing from pole s to pole t. In the four-pole driver, the output poles u and v are in the acoustic part. In this case the volume velocity flows from pole u to pole v. To pole u are connected all acoustic elements that are mounted on the front side of the diaphragm and have the same sound pressure at their input as across the diaphragm of the driver, for example the Radiator or Duct. All elements at the reverse side of the diaphragm receive the number of the node lying at the pole v. If the associated definition describes a loudspeaker in an enclosure, then, if the enclosure is mounted at the rear of the diaphragm, pole v must be grounded (0). If Driver refers to Def_TwoCoilsDriver, then the driver element is six-pole driver. Poles u and v are then also in the electrical network part and are the input of the second drive, in an analogous fashion to poles s and t. Poles w and x are now in the acoustic part. The simulation Inspect/Vol.-Velocity calculates the flow into the acoustical side of this multi- pole, i.e. the phase is inverted to the flow of those elements which are connected to these poles. The same applies to the Inspect/Velocity simulation.The Inspect/Pressure simulation displays the pressure across the acoustical poles, i.e. between the front and rearward side of the diaphragm.

11 21. február 2005 11 Povinné parametre DriverKeyword '...'Identifier. Def='...'Reference to associated definition. Node=s=t=u=vFour pole (Def_Driver, Def_PiezoDriver) The connection terminals of the driver are between poles s and t. The phase position of the radiated sound is inverted if the poles s and t are exchanged. Pole u is the front of the diaphragm, pole v its rear. Node=s=t=u=v=w=xSix pole (Def_TwoCoilsDriver) The connection terminals of the voice coil 1 are between poles s and t, those of the 2nd voice coil between poles u and v. The phase position of the radiated sound is inverted if the poles s and t or u and v respectively are exchanged. Pole w is the front of the diaphragm, pole x its rear.

12 21. február 2005 12 Def_Driver: Povinné parametre Def_DriverKeyword '...'Identifier of definition. Meas_...Keyword of mass load fs=...HzResonance frequency. Mms=...kgMass of diaphragm assembly. Cms=...m/NCompliance of suspension. Vas=...m3Equiv. volume of compliance to diaphragm suspension. Qms=...Mechanical quality factor of driver. Rms=...Ns/mMechanical resistance. Qes=...Electrical quality factor of driver. Bl=...TmConversion factor. Re=...ohmResistance of voice coil. dD=...mDiameter of driver diaphragm. SD=...m2Area of circular diaphragm. WD=...m HD=...mWidth and height of rectangular diaphragm.

13 21. február 2005 13 Def_Driver: Nepovinné parametre fre=...HzMakes Re frequency dependent to simulate the influence of eddy currents at high frequencies. ExpoRe=...Controles the resistance of the voice coil. Le=...HInductivity factor of voice coil. ExpoLe=...Controles the reactance of the voice coil. dD1=...mDiameter of inner diaphragm. SD1=...m2Area of inner diaphragm. tD1=...mDepth and height of cone and dome diaphragm, respectively. t1=...mDisplacement of diaphragm within baffle. fp=...HzMass reduction frequency of cone and dome diaphragms, respectively. Diffuse=...%Directivity control factor

14 21. február 2005 14 Def_TwoCoilsDriver: Povinné parametre Def_TwoCoilsDriverKeyword '...'Identifier of definition. Meas_...Keyword of mass load fs=...HzResonance frequency. Mms=...kgMass of diaphragm assembly. Cms=...m/NCompliance of suspension. Vas=...m3Equiv. volume of compliance to diaphragm suspension. Qms=...Mechanical quality factor of driver. Rms=...Ns/mMechanical resistance. Qes1=... Qes2=...Electrical quality factor of driver (first, second voice coil). Bl1=...Tm Bl2=...TmConversion factor of first and second voice coil. Re1=...ohm Re2=...ohmResistance of first and second voice coil dD=...mDiameter of driver diaphragm. SD=...m2Area of circular diaphragm. WD=...m HD=...mWidth and height of rectangular diaphragm.

15 21. február 2005 15 Def_TwoCoilsDriver: Nepovinné parametre fre1=...Hz fre2=...HzMakes Re1, Re2 frequency dependent to simulate the influence of eddy currents at high frequencies. ExpoRe1=... ExpoRe2=...Controles the resistance of the voice coils. Le1=...H Le2=...HInductivity factor of first and second voice coil. ExpoLe1=... ExpoLe2=...Controles the reactance of the voice coils. dD1=...mDiameter of inner diaphragm. SD1=...m2Area of inner diaphragm. tD1=...mDepth and height of cone and dome diaphragm, respectively. t1=...mDisplacement of diaphragm within baffle. fp=...HzMass reduction frequency of cone and dome diaphragms, respectively. Diffuse=...%Directivity control factor

16 21. február 2005 16 Def_PiezoDriver: Povinné parametre Def_PiezoDriverKeyword '...'Identifier of definition. Meas_...Keyword of mass load fs=...HzResonance frequency. Mms=...kgMass of diaphragm assembly. Cms=...m/NCompliance of suspension. Vas=...m3Equiv. volume of compliance to diaphragm suspension Qms=...Mechanical quality factor of driver. Rms=...Ns/mMechanical resistance. Cp=...FPiezo-capacitance F/U=...N/VConversion factor dD=...mDiameter of driver diaphragm. SD=...m2Area of circular diaphragm. WD=...m, HD=...mWidth and height of rectangular diaphragm.

17 21. február 2005 17 Def_PiezoDriver: Nepovinné parametre dD1=...mDiameter of inner diaphragm. SD1=...m2Area of inner diaphragm. tD1=...mDepth and height of cone and dome diaphragm, respectively. t1=...mDisplacement of diaphragm within baffle. fp=...HzMass reduction frequency of cone and dome diaphragms, respectively. Diffuse=...%Directivity control factor

18 21. február 2005 18 Enclosure

19 21. február 2005 19 Network element The Enclosure is a multi-purpose element, used to implement cavities, compliances and closed or vented loudspeaker enclosures in the network. The enclosure is usually rectangular. The entry for the enclosure depth is used to calculate the standing waves of the basic mode in at least one dimension. For non-rectangular enclosures, it is not possible to calculate the mode of vibration. In this case the enclosure is regarded as a linear acoustic spring force (which is certainly the case for low frequencies). The imaginary component of the radiation impedance (air load) of the enclosure is, in the non-rectangular case, provided by the entry for the acoustic mass over the cross-sectional area Sb=. Note, that in many cases the cavity can be easily approximated by a rectangular shape with regard to the standing wave pattern. Vented enclosure Enclosure becomes a reflex enclosure when the vent Length Len=, the vent cross section or the Helmholtz frequency fb= is entered. In this case, a radiation element is automatically created for the required vent. This radiation element should be positioned on the baffle with the customary position details (x=, y=,..). The vent is modeled as an acoustical duct similar the Duct-element. Apart from the radiation resistance and the loss resistance due to viscosity, the specification of the tunnel quality factor QD/fo adds further losses to the port. Helmholtz dialog The Helmholtz-dialog assists you in designing the reflex enclosure.

20 21. február 2005 20 Parametre Povinné parametre –EnclosureKeyword –'...'Identifier. –Node=sConnection pole of the enclosure. The other pole is always ground, i.e. the enclosure wall. –Vb=...m3Volume of enclosure. Nepovinné parametre –Qb/fo=...Enclosure quality factor divided by the frequency at which Qb has been measured, i.e. usually the Helmholtz resonance fb. –Lb=...mRectangular enclosure. When Lb= is entered, the enclosure is rectangular. The program calculates the standing waves in one dimension. –Sb=...m2Non-rectangular Enclosure. For the approximate determination of the air load that a non-rectangular enclosure presents to the connected sound sources.

21 21. február 2005 21 Special parameter for vented cabinets Povinné parametre –Len=...mLength of vent. When Len= is entered, Enclosure describes a reflex enclosure, otherwise a closed enclosure. If Len= is specified no end-correction takes place. –fb=...HzHelmholtz resonance of the reflex enclosure. When fb is entered, Enclosure describes a reflex enclosure, otherwise a closed enclosure. Len= is calculated by the Helmholtz formula including one sided end-correction of infinite baffle. –dD=...mDiameter of the vent opening. –SD=...m2Vent cross section area. –WD=...m –HD=...mWidth and height of a rectangular vent area. Voliteľné parametre –QD/fo=...Vent quality factor divided by the Helmholtz quality fb. –Visc=...Factor to switch off calculation of damping due to viscosity or to modify its strength. Off:Visc = 0, Default:Visc = 1, Decrease of damping:Visc = 0... 1, Increase of damping: Visc > 1 –LongRectangular vented enclosure. Keyword for a so-called 'long” reflex enclosure. For a reflex-enclosure the vent cross-section is to be entered. If no length and no fb is specified, AkAbak assumes Len=0. There is only the radiation impedance. –x=...m –y=...m –z=...mVented enclosure. Position of the center point of the external vent aperture area on the baffle. –HAngle=...° –VAngle=...°Vented enclosure. Mounting angles of the center point of the external vent aperture area on the baffle. –WEdge=...m –HEdge=...mVented enclosure. Diffraction. Width and height of the baffle. Has to be entered if Reflection has been entered. –ReflectionVented enclosure. If entered, the sound radiation is influenced by reflections. (see Def_Reflector) –NoRadNo radiation takes place from the vent. –NoDirVent radiates as a point source.

22 21. február 2005 22


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