Open Baffle w/ 2 Drivers - Acoustic Response 12/27/12. Copyright 2012 by Martin J. King. All Rights Reserved.

Transcription

1 Open Baffle w/ 2 Drivers - Acoustic Response 12/27/12 Software : by Martin J. King MJKing57@aol.com Copyright 212 by Martin J. King. All Rights Reserved. Configuration : Extended Range Driver w/ Bass Driver Mounted on an Open Baffle Unit and Constant Definition cycle 2πrad Hz cyclesec 1 Air Density : ρ 1.25kgm 3 Speed of Sound : c 344msec 1 Part 1 : Thiele-Small Consistent Calculation Detailed User Input (Edit This Section and Input the Parameters for the System to be Analyzed) Power 1watt (Input Power) Applied Voltage Reference ---> R ref 8Ω Extended Range Driver Thiele / Small Parameters : Fostex FE-13E f d R e L vc 79.5Hz V ad 6.9liter 7.45Ω Q ed.4.1mh Q md 2.87 Bl 4.42 newton 1 1 Q td amp Q ed S d π4 2 cm 2 Q td.351 Q md 1 Bass Driver Thiele / Small Parameters : Eminence Alpha 15" High Efficiency f d R e L vc 41Hz V ad 26liter 5.88Ω Q ed mH Q md 7.23 Bl 7.7 newton 1 1 Q td amp Q ed S d 856.3cm 2 Q td Q md 1

2 Instructions : 1. A Zobel, Trap, and L-Pad are available for adjusting the Extended Range Driver's SPL output. 2. Select the crossover frequencies, orders, and types below. 3. Scroll down to the applicable crossover sections below and fill in the values of the circuit components. a. The theoretical values are shown to the right of each schematic. b, Theoretical values are calculated using only the driver's DC resistance, a textbook solution. c. Enter the actual component values, these should correspond to available components. d. Iterate the actual component values to optimize the crossover responses. e. You can mix the crossover orders and types by using only half of each pair of schematics. 4. Purchase the optimized actual component values and construct the crossover per the schematics. Crossover Definition For Even Order Crossovers : Type 1 = Linkwitz-Riley Type 2 = Bessel Type 3 = BEC Type 4 = Butterworth Low Pass Filter High Pass Filter f LP 2Hz f HP 5Hz (Filter Frequency) LP order 2 HP order 2 (Filter Order :, 1, 2, 3, or 4) LP type 1 HP type 2 (Filter Type : 1, 2, 3, or 4 for even order only, for odd order this entry is ignored) Crossover Phase Connection and Extended Range Driver Attenuation LP phase 1 HP phase 1 (Phase : 1 = in phase, -1 = out of phase) L_Pad 1 db (L Pad Attemuation of Extended Range Driver)

3 Extended Range Driver Compensation Circuits (Default Actual Values Remove Circuits) Zobel Components User Specified Compensation Circuit Values Suggested Values R zobel Ω Actual Values R zobel 1 1 Ω C zobel.12 μf C zobel 1 1 μf Resonance Trap Components Suggested Values R trap Ω Actual Values R trap 1 1 Ω C trap μf C trap 1 1 μf L trap mh L trap 1 1 mh L-Pad Components Suggested Values R parallel Ω Actual Values R parallel 1 1 Ω R series.639 Ω R series Ω

4 Crossover Definition - 1 st Order High and Low Pass Schematic C1 + - Midrange Theoretical Values C μf + L1 Woofer L mh - Enter Actual Component Values Below High Pass C 1 4μF Low Pass L 1 4.5mH R 1.3Ω

5 Crossover Definition - 2 nd Order High and Low Pass Schematic C1 + L1 - Midrange Theoretical Values C 1 L μf 4.11 mh + - L2 C2 Woofer L 2 C mh μf Enter Actual Component Values Below High Pass C 1 L 1 25μF 4mH R 1.3Ω Low Pass L 2 C 2 1mH R 2.5Ω 68μF

6 Crossover Definition - 3 rd Order High and Low Pass Schematic Theoretical Values + - C1 L1 C2 Midrange C 1 L 1 C μf mh μf + - L2 C3 L3 Woofer L 2 C 3 L mh μf 2.34 mh Enter Actual Component Values Below High Pass C 1 L 1 C 2 28μF 1.75mH R 1.2Ω 85μF Low Pass L 2 C 3 L 3 7mH R 2.5Ω 18μF 2.5mH R 3.2Ω

7 Crossover Definition - 4 th Order High and Low Pass Schematic C1 C2 + L1 L2 Midrange - L3 L4 + C3 C4 Woofer - Theoretical Values C 1 L 1 C 2 L 2 L 3 C 3 L μf 1.53 mh μf mh 8.82 mh μf 4.41 mh Enter Actual Component Values Below C μf High Pass C 1 L 1 C 2 L 2 25μF 1.5mH R 1.1Ω 43μF 6.5mH R 2.3Ω Low Pass L 3 C 3 L 4 C 4 9mH R 3.5Ω 215μF 4.5mH R 4.3Ω 48μF End of Detailed Input End of Part 1 Input

8 OB Driver Impedance 9 Phase (deg) argz r deg Impedance (ohms) Z r r r Frequency (Hz) Driver RMS Displacements (Red Curve - Woofers, Blue Curve - Extended Range Driver) 5 RMS Deflection (mm) x Lr mm x Hr mm rdω Hz 1 Frequency (Hz)

9 Part 2 : Detailed SPL Response Calculation Calculation Includes : Position of Drivers on the Baffle. Open Baffle Defraction for the Drivers. Floor Reflection for the Drivers. Geometry Coordinate System : Origin is the lower left corner of the front baffle y = horizontal direction z = vertical direction The variables num_r, n_low, and n_high 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 2ft 1.5ft 45deg 8ft stand m num_r 1 (Front Baffle Distance from Rear Wall > Depth of Enclosure) (Front Baffle Distance from Side Wall) (Rotation Towards Room Center) (Floor to Ceiling Distance) (Height from Floor to Bottom Edge of Front Baffle) (Number of Points per Unit Length of Baffle Edge) Corner Coordinates Y coordinate Z coordinate y o y o1 y o2 y o3 2in 2in z o1 38in in z o2 38in in (Bottom Right Corner) (Top Right Corner) (Top Left Corner) (Bottom Left Corner) Extended Range Driver Geometry Input y dc z dc 8in 32in n_high 4 (Driver Center y Coordinate) (Driver Center z Coordinate) (Number of Points Across Diameter) Woofer Driver Geometry Input y w1 z w1 1in 1in n_low 1 (Lower Driver Center y Coordinate) (Lower Driver Center z Coordinate) (Number of Points Across Diameter)

10 Listening Position (Default Location is at 1 m Distance Along the Driver's Axis) n_listen = radius 1m θ z p deg z dc (Listening Position Relative to Speaker) (Calculation Radius, Effective Radius is Greater if y p is Changed from Default) ( deg is along the Driver's Axis, -8 deg < < 8 deg) (Default Height is Equal to Driver Height) n_listen = 1 X p Y p 1ft 7ft Z p z dc stand n_listen (Listening Position Relative to the Room Corner) (Default Height is Equal to Driver Height) (Method Selection) Floor Condition Reflect 1 ( = hardwood or concrete, 1 = carpeted) Refective Surface Selections (if 1 reflective surface is included, if reflective surface is removed) Inc_floor 1 (Floor, Z = ) Inc_rear (Rear Wall, X = ) Inc_side (Left Side Wall, Y = ) Inc_ceiling (Ceiling)

11 Extended Range Driver and Woofer : Simple Source Pattern with Baffle Edge Outline 1 z d z w z o y d y w y o

12 Three Dimensional View Axis Length (m) axis 2 <---- Change value of "axis" to rescale plots Room Corner is the Origin 2 Side view z driver 1.5 z outline z woofer 1 Side View - looking out from side wall z mic x driver x outline x woofer x mic 2 Front View z driver 1.5 z outline z woofer 1 Front View - looking towards rear wall z mic y driver y outline y woofer y mic 2 Top View y driver 1.5 y outline y woofer 1 Top View - looking down from ceiling y mic x driver x outline x woofer x mic

13 Plotted Response for the Extended Range Driver Dashed Red - Infinite Baffle Response Dashed Magenta - Baffle Response Dashed Brown - Crossover Response Solid Red - Combined Response SPL (db) 1 5 SPL IBr 5 X_over r 1 SPL 15 BFr 2 SPL nr rdω Hz 1 Phase (degrees) Phase r deg SPL (db) rdω Hz SPL Hr rdω Hz 1 Frequency (Hz)

14 Plotted Response for the Woofer Driver Dashed Red - Infinite Baffle Response Dashed Magenta - Baffle Response Dashed Brown - Crossover Response Solid Red - Combined Response SPL (db) 1 5 SPL IBr 5 X_over r 1 SPL 15 BFr 2 SPL nr rdω Hz 1 Phase (degrees) Phase r deg SPL (db) rdω Hz SPL Lr rdω Hz 1 Frequency (Hz)

15 Plotted System Response for the Extended Range and Woofer Open Baffle Design Phase (degrees) Phase r deg SPL (db) rdω Hz SPL r 1 95 SPL 9 Hr 85 SPL Lr rdω Hz 1 Frequency (Hz)

16 System Time Response for an Impulse Input 1 Woofer Sound Pressure in Time Domain p wooferr Pa rdt System Sound Pressure in Time Domain 11 3 p summedr Pa rdt Time (sec)

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