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Smith & Larson Audio Wofer Tester 2 User Manual

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Woofer Tester 2
User Guide

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Summary of Contents for Smith & Larson Audio Wofer Tester 2

  • Page 1 Woofer Tester 2 User Guide...
  • Page 2  Smith & Larson Audio PO Box 229 Savage, MD 20763 Phone +1 781.259.1804 • Email: tech@woofertester.com...

  • Page 3: Table Of Contents

    Table of Contents GENERAL INSTALLATION & SETUP .................... 5 1.1. 2 ................5 ETTING TO KNOW YOUR OOFER ESTER 1.2....................5 NSTALLING THE OFTWARE 1.3....................7 ETTING UP THE ARDWARE 1.4..................10 ONNECTING THE OOFER ESTER NAVIGATION ......................11 2.1........................12 2.2.
  • Page 4 4.9. )..............52 AUNCH FROM UTTON 4.10..................52 AKING UITABLE ENCH 4.11......................53 RIVER REAK 4.12. (ARB1 ARB2 B )...........54 RBITRARY MPEDANCE LOTS UTTON DRIVER SIMULATION AND BOX DESIGN..............55 5.1................55 IMULATION AND HYSICAL ESIGN 5.2....................56 IRST IMULATION IN-BOX ELECTRICAL TESTING................. 57 6.1.

  • Page 5: Installation & Setup

    INSTALLATION & SETUP 1. INSTALLATION & SETUP 1.1. Getting to know your Woofer Tester 2 Woofer Tester 2 Front The front of the test measurement box contains the speaker test load connections, a power indicator LED and a mini - jack (headphone) connector for supplying a break in test tone to an external amplifier.
  • Page 6 INSTALLATION & SETUP 2. Click Next. The next dialog box shows the license agreement. Please read it and select “I agree” if you concur and then click Continue to proceed with the installation. 3. Next, select an existing directory using Browse or create a new one by typing a name in the text box. The default action is to create a WT2 directory on your C: Drive.

  • Page 7: Setting Up The Hardware

    INSTALLATION & SETUP 1.3. Setting up the Hardware HWSETUP 1. To setup the hardware, connect the USB cable between the WT2 and computer’s USB port. Windows will indicate new hardware has been detected and the following dialog box pops open: 2.
  • Page 8 INSTALLATION & SETUP Additional Steps for Windows Vista Users When Windows Vista installs the ‘USB Audio Device’ driver, the initial default will be set for 1 channel 22 kHz. This must be changed for the Tester to operate properly. The changes made here may revert back if the operating system is updated, or a new audio device is installed.
  • Page 9 INSTALLATION & SETUP Repeat Step 4 for the ‘Playback’ tab (2 channel 44100 Hz sampling). Go to the ‘Enhancements’ Tab and make sure that the ‘Disable all enhancements’ checkbox is selected. Make sure that the Playback, Record and Woofer Tester sampling rates all match. 44100 Hz is the recommended sampling rate for Vista and is the default setting on the Woofer Tester.

  • Page 10: Connecting The Woofer Tester

    INSTALLATION & SETUP 1.4. Connecting the Woofer Tester ! WARNING ! DO NOT CONNECT ANYTHING EXCEPT FOR A DRIVER TO THE LOW POWER TEST PORT Basic Thiele Small testing and parameter extraction does not require more than a few milli-amps of current, which is easily powered by the USB port.

  • Page 11: Navigation

    NAVIGATION 2. NAVIGATION This section of the user guide gives an overview of the software features, explains how to view, print and expo rt results and configure system settings. Now that you have connected up your WT2 and started the software, you will see the main window shown below.

  • Page 12: Menu Bar

    NAVIGATION 2.1. Menu Bar On the top of the screen is the menu bar with eight pull - down menus from which you can perform the following functions: Menu Functions Open and create WOO Files (described in the next section), export results to various file formats File and capture graphics View...
  • Page 13 NAVIGATION Buttons with Multiple Click Regions Buttons can consist of multiple click regions. The first five buttons, Q/FS Test, Vas Test, Measure Box, Arb1 sweep and Arb2 sweep have two regions. Clicking the button on the left changes the data view in the main window. C licking the button in the middle or on the right conducts the test: Click on the left side of the button to switch the data view...

  • Page 14: Wt Control Window

    NAVIGATION 2.3. WT Control Window The WT control window consists of a results area on top and a graphing area on the bottom. The results area shows the output of the latest Q/FS, Vas and Box tests. The results area can be minimized or maximized using the [-] and [+] buttons. Minimize Maximize Text...
  • Page 15 NAVIGATION Buttons in the Graphing Area The graphing area displays sweep and real-time signals that are generated. There are two groups of buttons at the top of the graph; two in the left corner and three in the right corner labeled Setup, Auto and Data. Buttons Auto –...
  • Page 16 NAVIGATION Adding/Removing Datapoints from the Graph After you have measured a driver, depending on the number of data points used in the measurement, you might find pieces of a curve that are not smooth. The missing curve segments can then be smoothed out by adding additional measurement points: Options menu ...

  • Page 17: Setup Control Window

    NAVIGATION 2.4. Setup Control Window Calculation of Impedance Impedance is mathematically defined as the ratio of Voltage to Current. These signals are shown in the 'measured' and 'reference' signal columns as LoZP V and LoZP A. The other signal selection options (available for the Speaker Tester and Woofer Tester Pro) are blanked out.
  • Page 18 NAVIGATION The number of Windows buffers used and the number of frames used to create averaged results is set at the bottom of this window. Number Audio Buffers - Audio buffering requires at least two buffers, one for computing and one to be passed ...
  • Page 19 NAVIGATION Axis Control The Axis control tab is identical to the Axis dialog that opens when the left hand side of graph window is clicked except this is a child window. A child window allows you to select and work in other windows. The controls in this window include: X- display Extents: Low and high frequency limits ...
  • Page 20 NAVIGATION Overlay (Data Display) Control The Overlay tab is used to enable one data buffer for data entry in the TS Control child window and up to 32 data overlays in the Overlay child window. The first column is used to enable multiple overlays, and the second to enable the current destination buffer.

  • Page 21: Overlay Window

    NAVIGATION Calc +dB Offset, Calc +Ph Offset These buttons open the following dialog box. A frequency entered into the ‘Measure at’ field will fill the Measurement field with the value at frequency, in this case –13.2295. If the desired value at frequency is then 10.0, the required offset difference would be –13.2295-10 or –23.2295.

  • Page 22: T/S Entry Window

    NAVIGATION 2.6. T/S Entry Window The Thiele Small Entry window is used to both, design and verify box designs. Vent ed, sealed, passive radiator and band pass box models are supported. Other advanced features include the automatic alignment of the simulator to measured box values, simulation of frequency dependent inductance (Le, Rem, Xem), pipe resonance effects, various Q loss factors, small room and car boost effects, selection of TS models from compression tables and cable loss.

  • Page 23: X-Y Plot Window

    NAVIGATION 2.7. X-Y Plot Window The X-Y plot window is used to view and compare the THD and Thiele Small Parameters that are collected during the AC and DC compression tests as well as SINAD. The AC compression test creates a tabular list of driver TS parameters with increasing drive level (you can get this report from the Results pull down menu).

  • Page 24: View Menu Options

    NAVIGATION 2.8. View Menu Options View  from the menu bar gives the There are various ways to view the data and test results in the Woofer Tester. Selecting following list of viewing options, each of which is its own separate window: View View Name Function...
  • Page 25 NAVIGATION In addition to selecting data and test windows, the View menu contains a number of options to change attributes in these windows, such as applying Bezier Line Smoothing, setting the FFT Resolution, changing the line width in graphs, adjusting the color schemes and changing the legend.
  • Page 26 NAVIGATION View  Pick Colors Pick Colors option is used to change the color scheme of graphed data. The 16 Custom colors are arranged in 8 vertical pairs, with each pair corresponding to a pair of colors that can be used in the testers graphing windows. The first pair corresponds to the first of 32 data buffer pairs.
  • Page 27 NAVIGATION Select View  Change Legend from the menu bar to open the dialog box below. You will see some lines of text consisting of codes shown in [ ] and their assigned values. The codes determine the size and position of the legend text and whether pointers are drawn or not.
  • Page 28 NAVIGATION The following table lists all the codes available to create a legend: Function Syntax Description Draws an arrow from current position of the legend text to a specified [x,y] position. The x,y position can ARROWTO [ARROWTO(x,y,size)] be determined by a function, ie GETX or PVAL. Size is arrow point size Draws a box.

  • Page 29: Woo Files & Screen Configuration

    NAVIGATION Arranging the Test Windows Window menu option. When you have multiple windows open, a quick way to arrange them is via the The windows can be arranged vertically, horizontally or in cascading order. For example, with the Tile Vertical option, four open windows will arrange like this: 2.9.

  • Page 30: Viewing, Formatting & Converting Results

    NAVIGATION File  eXport  [Export Options] The tester exports data to a number of different file formats. ASCII – Exports data from all buffers and result windows to a text file.  BassBox – Exports Thiele Small parameter measurements to a .log file for import into BassB ox ...
  • Page 31 NAVIGATION Results  New Speaker Title Results  New Speaker Title menu option, you can modify the title in the WT Control Window. Selecting this With the option, opens a text dialog box. Enter the new title here and click OK. This will change the title as shown below: Results ...

  • Page 32: Options Menu

    NAVIGATION Results  Copy between buffers Copy For a simulation, it can be useful to be able to temporarily save a data set that is later used in a data overlay. Selecting the between buffers option opens the dialog box shown below. Choose the result set to be temporarily saved from the left-hand column. From the right-hand column, select the target buffer to hold the data and click OK.
  • Page 33 NAVIGATION The three point method finds two high frequency points near SweepHi that have a positive phase slope. This usually produces a better upper frequency fit, but it may not converge. High frequency negative phase slopes are created when the test lead inductance is significant compared to driver Le and the test leads are not calibrated or moved.
  • Page 34 NAVIGATION Options  Mute button includes AGC AGC stands for Automatic Gain Control and applies to drive level control. With AGC turned on, drivel level will increase to just below the clipping point. This feature is helpful for setting levels in high impedance circuits. When AGC is turned on, the mute button has three modes: MUTE, UNMUTED and UNMUTED –...
  • Page 35 NAVIGATION Options  Smoothing (All Real-time Modes) Select this option to turn FFT averaging on and off. When enabled, it smoothes response curves from noisy signals. Smoothing applies to Impulse, MLS, Noise, Chirp signals. Tip: Signal mode and Smoothing can also be set in the Setup Control Window Options ...

  • Page 36: Tools Menu

    NAVIGATION 2.12. Tools Menu Tools  Set Atmospheric conditions Atmospheric conditions that affect the calculation of Thiele Small parameters and the simulator response are set here. Inputs include temperature, humidity and atmospheric pressure. Outputs are density, speed of sound and acoustic impedance.
  • Page 37 NAVIGATION Tools  Design Air Core Inductor The air core inductor tool will help you design air core inductors for your crossover designs. Enter the desired inductance value in the first field and click enter. Input the inner diameter (D) - larger diameters produce lower inductance. Hit enter. Next, enter the height in inches (H).

  • Page 38: Printing Files/Graphs

    NAVIGATION Tools  Auto-Set (Windows Vista Users only) This menu option resets the current mixer levels to the values specified in the “MIXERLVL.CFG” configuration file. The message on the right appears on startup if the mixer settings do not match the specified levels. The message asks you to confirm changes in mixer settings.

  • Page 39: Exporting Results

    NAVIGATION 2.14. Exporting Results Test data can be exported in a number of formats. The export type will depend on what you want to do with the data. A common export is a ZMA files that is used in the Interactive Crossover Designer. 2.15.

  • Page 40: Calibration

    CALIBRATION 3. CALIBRATION CAUTION: You may not want to connect an amplifier to the tester until you are familiar with the tester and using/calibrating the low power test port. 3.1. Calibration, Component & Linear Testing The low power port must be calibrated to use the tester. For best results, calibrate both the High and Low Test ports. Two calibration routines are run for each port.
  • Page 41 CALIBRATION Low Power Calibration Steps The first dialog that opens will ask for you if you want to perform a full or simple calibration. Both methods are similar in that they will use the calibration resistor and or short to set the testers internal gains and offsets. The difference is that in the full calibration mode the test leads inductance and resistance are measured.
  • Page 42 CALIBRATION Note: Measurements are not instantaneous. High-level noises around the test area are rejected using tuned narrow band filters. This slows down the calibration. The 1-10 Hz band is particularly slow and takes several seconds to complete. Wait until the ‘Check Connections’ message changes to ‘Pass‘ before hitting NEXT. Process Step Setup Info Wait for...
  • Page 43 CALIBRATION Step 4/5 is another shorting test. In full calibration mode the cable is inserted into the circuit and measured using a short at the far end. This physical configuration is already setup for the simple calibration mode. Wait for ‘Pass’ and press NEXT.
  • Page 44 CALIBRATION Low Power Port Voltage and Amperage Calibration Impedance and phase calibration tunes the voltage and current ratio on an absolute scale. This test must be run from the Test pull down menu. Leaving the 10-ohm calibration resistor connected to the low power port, choose Tests ...

  • Page 45: Capacitor Measurement

    CALIBRATION 3.3. Capacitor Measurement The menu option Tests  Capacitor Measurement Setup , is used to fine-tune the low power port for measuring small value capacitors. Crossover capacitors are typically quite large compared to the internal capacitance of the test port tha t is around 350-550 pF.

  • Page 46: Thiele-Small Driver Measurement

    THIELE-SMALL DRIVER MEASUREMENT 4. THIELE-SMALL DRIVER MEASUREMENT ! WARNING ! The Woofer Tester’s DIFFERENTIAL CURRENT SOURCE OUTPUT (BANANA JACK) is not ground referenced and cannot be safely connected to grounded or externally powered equipment without risking damage to the device. This applies to Amplifiers and Oscilloscopes. Simple ‘two terminal’...

  • Page 47: Driver Q

    THIELE-SMALL DRIVER MEASUREMENT         where Fs = Mechanical system resonance in Hertz (also known as Fms) Kms = Mechanical system spring stiffness in Newtons/Meter Mms = Mechanical system moving mass in kg Electrically, the tester sees a mechanical resonance as a parallel circuit consisting of a capacitor and inductor with an additional resistor (the voice coil) in series.

  • Page 48: Driver Frequency Dependent Inductance (Le Is Not Simple Inductance)

    THIELE-SMALL DRIVER MEASUREMENT Zmax    Zmax    Qes) 4.4. Driver Frequency Dependent Inductance (Le is not simple inductance) The next evolution in T/S modeling includes voice coil inductance ‘Le’. When Le is added to the standard T/S model, it not only affects response but it also causes Fs to shift upward in frequency.

  • Page 49: The Thiele Small Tests (What Is Measured)

    THIELE-SMALL DRIVER MEASUREMENT The AC drive level test relies on the testers ability to measure a very accurate baseline driver model. For example, if the tester can accurately measure Fs variation with drive level, and Mms is assumed to be constant, any variation in Fs must be attributable to variations of the driver suspension compliance Cms.
  • Page 50 THIELE-SMALL DRIVER MEASUREMENT Q,Fs ‘Free Air’ Test DC resistance Re is found by measuring the complex impedance at two low frequency points, calculating the real component at each frequency and then interpolating to zero hertz. The test port uses 1 and 2 Hertz as the test frequencies. Coefficients for Rem and Xem (frequency dependent Le) are found next by making one or more high frequency measurements.

  • Page 51: Vas Test (Launch From 'Vas Test' Button)

    THIELE-SMALL DRIVER MEASUREMENT 4.8. Vas Test (Launch from 'Vas Test' Button) VASTEST VAS testing requires that you modify the free air set up using one of three options. As before, the test begins by clicking in the middle of the Vas Test button. The delta mass or delta compliance methods are most popular, while the third, calculating Vas from a known efficiency, is most useful when creating electrical models for mid ranges and tweeters.

  • Page 52: Box Test (Launch From Box Test Button)

    THIELE-SMALL DRIVER MEASUREMENT The ‘Easy Nickel Test Mass’ method is particularly helpful for acquiring suitable test masses. Newly minted US Nickels have weighed 5.0 grams since 1938! If a lighter mass is needed, the copper coated zinc pennies (after 1983) are 2.5 grams. The following link contains information for US, European Euro, Australian and other coins.

  • Page 53: Driver Break-In

    THIELE-SMALL DRIVER MEASUREMENT Some floors (even concrete) will resonate strongly. This has to do with the mass to stiffness ratio an d loss factors for the particular test point. The center and corners of a table would be an example where the leg at the corner substantially increases stiffness.

  • Page 54: Arbitrary Impedance Plots (Arb1 And Arb2 Button)

    THIELE-SMALL DRIVER MEASUREMENT ! WARNING ! MECHANICAL OVERDRIVE IS PARTICULARLY EASY TO DO WHEN FREQUENCY IS SET BELOW FS. FS ALSO TENDS TO DROP WITH BREAK-IN. Begin with a moderately low level for the first 15 minutes and then slowly increase level. Mechanical resonance should be visible to the naked eye.

  • Page 55: Driver Simulation And Box Design

    DRIVER SIMULATION AND BOX DESIGN 5. DRIVER SIMULATION AND BOX DESIGN 5.1. Simulation and Physical Box Design A simulation is initially performed using the driver’s measured Q/Fs and Vas test data to find a suitable box alignment. In theory, the effective box volume and tuning will align with the physical but this is rarely exact.

  • Page 56: First Pass Simulation

    DRIVER SIMULATION AND BOX DESIGN 5.2. First Pass Simulation Box design begins by copying the test environment driver parameters (Q/Fs and Vas test data) into the simulator using the Copy- >Simulator button. A dialog box will then open asking you if you want to copy the Q/Fs, Vas and Box data. Check the ‘Q/Fs’ and ‘Vas’...

  • Page 57: In-Box Electrical Testing

    IN-BOX ELECTRICAL TESTING 6. IN-BOX ELECTRICAL TESTING 6.1. Box Electrical Test A very useful simulator feature is the ability to compare simulated and measured in-box impedance curves. When the two are aligned, the simulators box volume and tuning are said to be the effective box volume and tuning, but more importantly the simulated response will accurately reflect the measured response.

  • Page 58: Simulated Versus Measured In-Air Response

    IN-BOX ELECTRICAL TESTING Constrain Vbox When box volume is large compared to Vas, the driver compliance dominates the box air spring compliance. In this case small variations in Cms would cause significant errors in the estimated box volume method. This method is similar to the ‘Vas from a vented box’...

  • Page 59: Advanced Thiele Small Testing: Ac Compression

    IN-BOX ELECTRICAL TESTING 7. ADVANCED THIELE SMALL TESTING: AC COMPRESSION 7.1. AC Compression Testing To measure suspension non linearity versus AC level select the following menu option: Tests  Linearity Tests  Measure TS versus AC Level This test requires a precision low power TS baseline before the test begins (this is not automated and must be done first). This baseline establishes the driver’s moving mass, Re and motor constants.
  • Page 60 IN-BOX ELECTRICAL TESTING A careful examination of AC and DC results will often show a wide range of input levels, usually up to the point where suspension limiting begins, where the suspension mechanical spring constant (inverse of compliance) significantly decreases as the AC test signal level is increased.

  • Page 61: Test Tools And Calculators

    TEST TOOLS AND CALCULATORS TEST TOOLS AND CALCULATORS The tools and calculators mentioned in other chapters are described in greater detail in this chapter. 8.1. Aligning the Tester For Measuring Capacitors The Woofer Tester measures a very wide range of resistors, inductors and capacitors when properly configured. Since the tester’s constant current output produces an output voltage proportional to load impedance, some care must be taken when impedance becomes large.
  • Page 62 TEST TOOLS AND CALCULATORS This table shows the results of measuring a 100pF+/-2%, 1200pF+/-2%, and 2.0uF+/-2% capacitors. The 2uF capacitor was measured plugged directly into the tester as well using the supplied test leads. Note: Wiring can have a measurable effect. Frequency 100pF+/-2% 1200pF+/-2%...

  • Page 63: Zobel Calculator

    TEST TOOLS AND CALCULATORS 8.2. Zobel Calculator ZOBEL Zobel compensation networks negate the rising driver impedance caused by series inductance L e. Le is, however, a function of frequency and even includes frequency dependent resistance. In addition, the target impedance might not be Re, but an arbitrary value.

  • Page 64: Demonstration Files

    DEMONSTRATION FILES DEMONSTRATION FILES 9.1. Conducting a Simple Electrical Test 1. Connect the test leads to the Woofer Tester 2 and to the driver as shown below. 2. Double-click the SL icon on your desktop to launch the Tester application 3.

  • Page 65: Thiele-Small Simulator & Box Design Demonstration

    DEMONSTRATION FILES 9.2. Thiele-Small Simulator & Box Design Demonstration To use the Thiele-Small Simulator, leave the tester connected. The WOO file used in this demo contains previously acquired data for a 165 mm (6.5 inch) computer sub-woofer. Additional in-air data was also taken to show how the simulated and actual response will eventually align.
  • Page 66 DEMONSTRATION FILES Box values Driver T/S parameters Box types Buffer select Simulation models Acoustic Simulation Output What-if Simulated Response What-if Simulated Acoustic Phase 3. At this point, the TS parameters are preloaded into the simulator environment and you can begin modifying the box volume, tuning and port dimensions to achieve the desired response.
  • Page 67 DEMONSTRATION FILES 6. After building the box and measuring the in-box electrical characteristics, you don’t actually know if your physical box design has measured up to your ‘what-if’ design. Reasons for this include potential box dimension or port size errors, forgetting to include the volume displacement of the driver/bracing, or an interaction of the port or driver to the cabinet walls.

  • Page 68: Digital Signal Processing Terminology And Concepts

    DIGITAL SIGNAL PROCESSING TERMINOLOGY AND CONCEPTS DIGITAL SIGNAL PROCESSING TERMINOLOGY AND CONCEPTS A number of signal processing algorithms are used with the tester. The terminology and signal processing concepts are not difficult to understand and may lead to a better understanding of digital audio. 10.1.
  • Page 69 Index AC Compression Test, 23, 33 Delta Mass Test, 51, 52 AC Level, 59 AC Response, 23 Displacement, 52, 56, 59, 67 Air Core Inductor, 37, 38 DRAWX, 28 Amplitude Modulation, 68 Drive Level, 13, 33 Drive Signal ARROWTO, 27, 28 Atmospheric conditions, 36 Impulse, 34, 35...
  • Page 70 DIGITAL SIGNAL PROCESSING TERMINOLOGY AND CONCEPTS Gating Control, 13, 20, 21 Non-Linear Suspension, 3, 48 GETX, 27, 28 Nyquist Sampling Theorem, 4, 68 Graph Axis Control, 24 Octave Binning, 19 High Power Test, 49 OFF, 27, 28 High-Q Filter, 68 Offset, 21 ON, 27, 28 Options Menu...
  • Page 71 ROW, 28 Up-Sampling Filter, 4, 68 Up-Sampling Filters, 4, 68 Sample Rate, 35 US Nickel, 51, 52 Setup Control Window, 15 Overlay Tab, 20 Size&Comp Tab, 13, 20 View Menu Signal Mode, 34 Pick Colors, 26 Simulation, 4, 23, 52, 56, 65, 66 Reset Colors, 26 SINAD, 23, 29, 59 SIZE, 27, 28...

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