扬声器等效模型

1、扬声器等效模型You can simulate the behaviour of a speaker and its crossover by professi onal speaker desig n software. In case you do not have access to these software, an alter native would be to use the SPICE simulatio n software to do the speaker simulatio n. Here I will dem on strate how to do this usi

2、ng OrCad.There is a demo version of OrCad release 10 which you can download from Orcad's web site to try.Thiele-small eqivale nt circuitBefore you can simulate your driver in Orcad, you n eed to calculate the eqivale nt circuit for your driver unit. This circuit can be derived from the Thiele-sm

3、all parameters.For example, if a driver has the follow ing Thiele-Small Parameters :Thiele-Small ParametersRevc5.8 ohmsDC resista nee of voice coilLevc0.55mHvoice coil in ducta neeBl6.5T.mforce factorQts0.35total QQes0.45electrical QQms1.55mecha ni cal QFs37 Hzres onant freque ncyMmd0.014 kgmass of

4、cone + voice coil + etcRms2.08resista nee of suspe nsionCms1.34 mm/Ncomplia nee of suspe nsionSd0.0136sq.meffective cone areaVas0.0347cu.mequivale nt acoustic volumeXmax0.004mlin ear travel of voice coilFR37 -5000kHzfreque ncy resp onseVd0.0005cu.mdriver un it volume displaceme ntThen this driver ca

5、n be modelled with the following circuit :+Lc-r5 卄二:21.21 J7Some of the circuit values above are already obvious. Veg representsthe amplifier and is assumedtohave no output resista nee. The remai ning values were calculated from,Cmes = Mmd/(BI*BI) = electrical an alog of driver mecha ni cal cone mas

6、sLces = Cms*Bl*Bl = electrical an alog of driver mecha ni cal suspe nsion complia neeRes = Bl*Bl/Rms = electrical an alog of driver mecha ni cal suspe nsion resista nee Cmef = 8*po*Ad*Ad*Ad/(3*BI*BI) = electrical analog of air load on the driver unit's cone where:po = air den sity = 1.18 kg/cu.m

7、Ad = effective radius of the driver unit's cone = Square Root of (Sd/3.14)Some of these parameters can be look up from the driver's specification. This missing one could be calculated using the Un ibox excel file. Uni box is a free tool that can help you to desig n speaker en closure.drive U

8、nit Farsmeters1J (La)讪LU帕 No min日 I PcivverFafameteri orf Si nlt UnitWPL at 1 W 1 mi deEPLst 2.S3 Vrws 1?Mbk SFLst 60 W106.1 dIBQts0.339Ettfeetl Cits0.339lYlms13.02 gCms1.6S2 mrn/lH口 EM1.H20 kg/sElBSD TmRf. efficiency! nD0.415 %Ettieii-sncy. n0.415 %Applied voltage13.73 YTrns匚on startsf i g TinUniBo

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10、t Nondirettisnal Rangeall conrtants to default values曲me |Fw |口巨mi QB Datm Pm兰昌rive Unit CcnfigurationFR NfTctEd by L旦"L旦乞冃旦2：FR atfwctwT By WKtsrn曲 gq；ReadyVbUFL迪 PP啊130.0I i VIEl MGSowker Dezci门 /flo迫dVented Box /PR BaocBoxtdttlNUMSpeaker Driver Unit Simulatio nAfter you created your driver m

11、odels, you could start by testing if your driver model's impedance response is similar to your driver's actual impedance response. Now you need to familiar yourself with OrCad if you have not used it before. Here is a great Orcad tutorial that I suggest you to read if you have not used Orcad

12、 before.You can save some time by dow nl oad ing my Orcad project a sin gle driver un it, just cha nge the RLC values and you can start trying OrCad simulation right away.Let's do the woofer as an example. First, start up Orcad Capture and create a new empty project. The n in the schematic draw

13、the driver model using Place->Part. comma nd. The R, L and C are all un der theANALOG library. (You may need to add all libraries first if you have not done it.) Then add the AC voltage source (called AC un der the SOURCE lib.) and also add a ground refere nee by Place -> Groun d. -> O/Sour

14、ce. Connect all comp onents by Place->Wire. You should now have a circuit similar to the one below :込 Capture CIS - Demo Edrtion |X3e Edit yevj Bsce 巴白cfo Ppice Icoessories 2F*tions 述inda啊 Helpn xCP/ (SCHEMATIC1 : PAGE1)oLet's do some simulatio n: Add a new simulatio n pro select PSpice->

15、New Simulatio n Profile, type in a name. A simulation settings dialog will pop up. In the Analysis tab, set Analysis type to AC Sweep/Noise. Select Logarithmic, start freque ncy of 10H z, End Freque ncy of 20kH z, Poi nts/Decade to 50. Click OK.Simulation Settings - testAndlysis Configuration Files

16、Options Data Col tec HonFroLe WindowAnali*d: "p*| AC Gweep4d&iseOptions:S General GettingfCtLimeafLogs rithnicD迪朮A匸 Siveep TypeNoise AnalysisEnabledzfsquentjJ!E.nd Frequency:PcintsDecadffMcnte 匚arloAV wsl Case 匚 Parametric SepT emperat ur® S ieepBias PointEli 萊 PoirtIN S nurce.I rrt&am

17、p;rvel:Output Fife CpdonsInclude detailed bia$ point infoimationfor iwnlinesr coii foiled sour ces and semi corid u clots 10F1C*r»celHelpApplyNow place a voltage probe and a curre nt probe at in put of the of the resistor, by selecti ng PSpice -> Markers -> Voltage Level, and then point t

18、he probe at the line between the AC and the resistor. Select PSpice -> Markers -> Curre nt into Pin, and select the in put pin of the resistor.Select PSpice -> Run to start simulation. After the simulation is done, the result will pop up in another PSpice A/D win dow. Now you can see the vo

19、ltage and curre nt that go intothe driver at differe nt freque ncy. To get a impeda nee plot, you have to add a trace, by select ing Trace -> Add Trace, the n type V(V2:+)/l(R1) in the Trace Expressi on in put line, the n OK. Now you should see the driver un it's impeda nee vs freque ncy, lik

20、e the one below.C-11-H 1._ _ _ J _ _ _ _ _ 1 _ ,11.1rj"|111Jr| 1fi勺匸 14: tJ1JT十 11J1 11 于11-40 匚.z1iIN. 牙:- - - - H -' L T 1._- _- _ - -_ - 一 一 JII _ .-二土二二二| i|1CC二nBn 1011?n U（U2;*-7|仙眦1.G） J KR1） 7 U（U2：*）/r（R1）Fr equvneuKHz1You can compare the result to the impeda nee plot from the driv

21、er un it's datasheet, or better yet, compare it to your measured impedanee. If they look similar, then this should be a good model to use, if not, tune your circuit's RLC value un til they are close eno ugh.Crossover + Drivers Simulatio nAfter you have done your woofer and tweeter simulation

22、, you can add your crossover to the schematic. I separatedthe driver units and the crossover into 2 pages, you can do this by using the Place -> Off-Page conn ector to connect the 2 pages. My speaker has 2 woofers conn ected in parallel, as show n in the schematic below.3/JSCHEMAT1C1 :PAGE2)Wwter

23、l27 uYou can use the db Voltage probe to check the freque ncy resp onse of each in dividual drive un it. If you want to check total resp on se, you n eed to sum the 2 outputs of the crossover.In some crossover desig n, you will have to reverse the polarity of the tweeter. You can simulate this in Or

24、ead by either changing the polarity of the voltage source of the tweeter circuit (Set the phase property of the VAC to 180 degree), or you can add a FTABLE part to change the phase of the signal before it goes into the SUM part.Below is the freque ncy of the dB voltage resp onse of crossover + tweet

25、er + wooferIll 43»U.VIIz仁0蓟血20抽肚14-OHHzI VLLI LK u : DU( J(VJUUI-Llt1 )JDUI )>h requencuYou can also check the phase resp onse by putt ing a phase of voltage probe to the output.CF-5Bd-1Q?J-1S4d1 Ue.EJHZ nUCVWEEltR) t> F(«(VDUFtR1)1 9VKI12 pu(surv -our)Ff社誉1甘怕t弓Now you have simulated

26、 a perfect model of a speaker driver, but real speaker units do not give smooth and flat resp on se. I simulated the peaks, dips and n atural roll off of a speaker by using the FTABLE part to add resp onse variati on at differe nt freque ncies.You could also use FTABLE to adjust the sen sitivity of

27、the tweeter/woofer unit by add in g/subtract ing a few dB across the en tire freque ncy range :After I added the FTABLE to both the tweeter and woofer I ran the simulation again:'TABLEMOOCH? 4Wooferl9nu3D Hr35He40Hz43 M=5OHs60 Hz120 Hz500 H=IDDDHe1IDDH2DD心 ODDDD o OD341 3513-0iC'DOHz30DOH?4000HzfODOl-lzAfter I added the FTABLE to both the tweeter and woofer I ran the simulation again:B1Sdfi