Driver in a H Frame Transmission Line - Acoustic and Electrical Response 4/26/11. Copyright 2011 by Martin J. King. All Rights Reserved.

Transcription

1 Driver in a H Frame Transmission Line - Acoustic and Electrical Response 4/26/ Software : by Martin J. King MJKing57@aol.com Copyright 2 by Martin J. King. All Rights Reserved. Line Configuration : Near End Open -> Driver in the Line -> Far End Open Unit and Constant Definition cycle 2πrad Hz cyclesec Air Density : ρ.25kgm Speed of Sound : c 44msec Part : Thiele-Small Consistent Calculation Detailed User Input (Edit This Section and Input the Parameters for the System to be Analyzed) Woofer Series Resistance R add.5ω Input Power Power watt (Input Power) Applied Voltage Reference ---> R ref 8Ω Extended Range Driver Thiele / Small Parameters : Lowther PM2C f d 65.4Hz V ad 8.liter R e 6.9Ω R add Q ed.28 R e L vc mh Q md 2.96 Bl 9. newton Q td amp Q ed Q md S d 26cm 2 Q td.27 R e R add Bass Driver Thiele / Small Parameters : Two AE OB5 Woofer, Series VC's, in Parallel f d 2.286Hz V ad liter R e.5.ω R add Q ed.9 R e R e R add L vc.5.499mh Q md 6.97 Bl.2 newton Q td amp Q ed Q md S d 2855cm 2 Q td.884

2 H Frame Enclosure Geometry Definition : Model of Internal Air Volume L in ξ 2 ξl (Total Length of the H Frame) 2. in (Fraction of the Total Length of the Front Cavity :. < <.999) S 25.75in5.75in S L 25.75in5.75in (Area of the Driver End) (Area of the Open End) Density F lb ft (Front Stuffing Density : lb/ft < D < lb/ft ) Density R lb ft (Rear Stuffing Density : lb/ft < D < lb/ft ) Crossover Definition For Even Order Crossovers : Type = Linkwitz-Riley Type 2 = Bessel Type = BEC Type 4 = Butterworth Low Pass Filter High Pass Filter f LP Hz f HP 2Hz (Filter Frequency) LP order HP order 2 (Filter Order :,, 2,, or 4) LP type 4 HP type (Filter Type :, 2,, or 4 for even order only, for odd order this entry is ignored) Crossover Phase Connection LP phase HP phase (Phase : = in phase, - = out of phase) Low Frequency Boost LP boost 8 db Sub High Pass Filter f sub 2Hz (Filter Frequency) SHP order (Filter Order :,, 2,, or 4) SHP type 4 (Filter Type :, 2,, or 4 for even order only, for odd order this entry is ignored) End of Abbreviated User Input

3 Resulting Acoustic Impedance for the H Frame - Front Cavity Impedance Magnitude Impedance Phase () Z alfr ρc arg Z alfr rdω Hz 8 rdω Hz Velocity at the Terminus of the H Frame for a m/sec Excitation at the Driver - Front Cavity Epsilon Magnitude ε Fr. 8 rdω Hz Epsilon Phase () arg ε Fr rdω Hz

4 Resulting Acoustic Impedance for the H Frame - Rear Cavity Impedance Magnitude Impedance Phase () Z alrr ρc arg Z alrr rdω Hz 8 rdω Hz Velocity at the Terminus of the H Frame for a m/sec Excitation at the Driver - Rear Cavity Epsilon Magnitude ε Rr. 8 rdω Hz Epsilon Phase () arg ε Rr rdω Hz

5 H Frame and Infinite Baffle Woofer Impedance Solid Red is the H Frame Impedance Solid Blue is the Extended Range Driver Impedance Dashed Red is the Woofer Infinite Baffle Impedance 9 arg z Lr 45 Phase () arg z Hr arg z or 45 9 r Impedance (ohms) z Lr z Hr z or r

6 Driver RMS Displacements Solid Red is the H Frame Woofer Response Solid Blue is the OB Driver Response 2 RMS Deflection (mm) x Lr mm x Hr mm 5 5 rdω Hz

7 Part 2 : Detailed SPL Response Calculation Calculation Includes : Position of Front Terminus and Rear Terminus on the Baffle. Baffle Step Defraction for the Front Terminus and the Rear Terminus. Room Reflections for the Front Terminus and the Rear Terminus. Geometry Coordinate System : Origin is the lower left corner of the H Frame y = horizontal direction z = vertical direction The variables num_r, n_drv, and n_mth control the number of simple sources used in the calculations. Increasing each will improve accuracy at the expense of longer calculation times. Increase each variable until final plotted SPL stops changing at which point the solution has converged. Enclosure Geometry Input X Y θ Z 4.5ft 2ft 8ft (Front Baffle Distance from Rear Wall > Depth of Enclosure) (Front Baffle Distance from Side Wall) (Rotation Towards Room Center) (Floor to Ceiling Distance) stand m num_r 2 (Height from Floor to Bottom Edge of Front Baffle) (Number of Points per Unit Length of Baffle Edge) H Frame Geometry Input H width 27.25in H height 7.25in depth L.75in y c z c 7.25in 8.625in w mth 25.75in n_mth 2 (H Frame External Width) (H Hrame External Height) (H Frame External Depth) (Terminus Center y Coordinate) (Terminus Center z Coordinate) (Terminus Width) (Number of Points Across the Width) Extended Range Driver OB Geometry Input OB width OB height y dc in 2in 2in (OB panel width) (OB panel height) (Driver Center y Coordinate w.r.t. lower left corner of OB) z dc 2in (Driver Center z Coordinate w.r.t. lower left corner of OB) ξ ob 2in depth (Fraction of the Total Depth of the H Frame :. < <.999) n_high 5 (Number of Points Across Diameter)

8 Listening Position n_listen = radius θ z p m 29.25in (Listening Position Relative to Speaker) (Calculation Radius Along Axis of the Extended Range Driver) ( is along the Driver's Axis, -8 < < 8 ) (Default Height is Equal to Seated Height) n_listen = X p ft Y p Z p 7ft in n_listen (Listening Position Relative to the Room Corner) (Default Height is Equal to Seated Height) (Method Selection) Floor Condition Reflect ( = hardwood or concrete, = carpeted) Refective Surface Selections (if reflective surface is included, if reflective surface is removed) Inc_floor (Floor, Z = ) Inc_rear (Rear Wall, X = ) Inc_side (Left Side Wall, Y = ) Inc_ceiling (Ceiling)

9 H Frame and Extended Range Driver Simple Source Pattern with Baffle Edge Outline Front View.5 z fm z d z o y fm y d y o Side View.5 z fm z rm z d z o x fm x rm x d x o Blue sources represent extended range driver. Red sources represent front terminus. Red sources represent the rear terminus. Black outline represents the baffle edge. Origin is at the bottom front left corner of the enclosure.

10 Three Dimensional View Axis Length (m) axis 2.5 <---- Change value of "axis" to rescale plots Room Corner is the Origin Side view z front 2 z outline z rear z driver z ob Side View - looking out from side wall z mic 2 x front x outline x rear x driver x ob x mic

11 Front View z front z outline 2 z rear z driver z ob Front View - looking towards rear wall z mic 2 y front y outline y rear y driver y ob y mic Top View y front y outline 2 y rear y driver y ob Top View - looking down from ceiling y mic 2 x front x outline x rear x driver x ob x mic

12 Plotted Response for the Extended Range Driver 8 2 Phase (rees) Phase r SPL (db) rdω Hz SPL Hr rdω Hz

13 Plotted Baffle Step and Reflection SPL Response for the Front Terminus 8 2 Phase (rees) Phase r SPL (db) 8 rdω Hz SPL r rdω Hz

14 Plotted Baffle Step and Reflection SPL Response for the Rear Terminus 8 2 Phase (rees) Phase r SPL (db) 8 rdω Hz SPL r rdω Hz

15 Plotted SPL Response for the H Frame 8 2 Phase (rees) Phase Lr SPL (db) 8 rdω Hz SPL Lr rdω Hz

16 Plotted SPL Response for the System 8 2 Phase (rees) Phase r SPL (db) 8 4 rdω Hz 5 SPL r 95 SPL 9 Hr 85 SPL Lr rdω Hz

17 System Time Response for an Impulse Input H Frame Sound Pressure in Time Domain 2 p framer Pa rdt System Sound Pressure in Time Domain 2 p summedr Pa rdt Time (sec)