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DaytonAudio WT3 Online User's Manual

Woofer tester
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Online User's Guide
Revised: May 11, 2008
WT3 is produced by:
Dayton Audio
725 Pleasant Valley Drive
Springboro, Ohio 45066 USA
http://www.daytonaudio.com
Copyright © 2007-2008 by John L. Murphy, Andersonville, TN USA All Rights Reserved.
No part of this publication may be reproduced without prior express written permission.

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  • Page 1 All manuals and user guides at all-guides.com Online User’s Guide Revised: May 11, 2008 WT3 is produced by: Dayton Audio 725 Pleasant Valley Drive Springboro, Ohio 45066 USA http://www.daytonaudio.com Copyright © 2007-2008 by John L. Murphy, Andersonville, TN USA All Rights Reserved.
  • Page 2 A PC with a processor running at no less than 500 MHz with 64 MB RAM • One available USB port • A display with resolution of at least 800 x 600 pixels • WT3 runs under Microsoft Windows 98, Me, 2000, XP and VISTA operating systems.
  • Page 3 Only connect the WT3 to an unconnected loudspeaker. Naturally, you will want to test your first woofer as soon as you get your WT3. Here are step-by-step instructions to get you going quickly. 1) Install the WT3 software.
  • Page 4 "Impedance Analyzer" menu and following the on-screen instructions. 7) Connect the alligator clips from the WT3 unit to the terminals of the driver under test. The driver MUST NOT BE CONNECTED to an amplifier or other equipment. The connection polarity does not matter.
  • Page 5 10) After measuring the driver you can: Save the data to one of 20 project memories. • Save your work to a WT3 test project file (file type .wt3) which includes your test setup • and all 20 memories. Export the impedance and phase data in either .txt or .zma formats. Parameters are •...
  • Page 6 All manuals and user guides at all-guides.com Windows Vista - Additional Setup Requirements PLEASE NOTE: STEP 2 IS CRITICAL FOR WINDOWS VISTA USERS! 1. Go to the Windows Control Panel and open the “Sound” control panel. At the "Playback" tab make sure that "USB Audio Codec"...
  • Page 7 3. Click OK to close the "Sound" control panel. Note that this setup must be performed once for each USB port with which the WT3 unit will be used. Also, when starting WT3, always click on the Speaker icon in the task bar and make sure the Windows...
  • Page 8 1%. The WT3 software is supplied on a CD. The software runs under Windows and provides an easy to use interface that allows users to be up and running quickly. When the software is launched it opens with an Untitled Project file.
  • Page 9 All manuals and user guides at all-guides.com The WT3 Toolbar The WT3 Toolbar provides easy access for many frequently used commands. Memory show and hide operations are especially convenient with the toolbar. Note that empty memories are grayed out until data is saved to them.
  • Page 10 (test box volume, added mass etc.) along with the three pages of parameters, ,specifications and comments that are seen at the Driver Editor. When you save a WT3 file (type ".wt3") to disc this measurement project file contains all the measurements in the projects 20 memories as well as the data currently on the Workbench.
  • Page 11 General Information page and in the Notes field below the plot window. Entering a line or two of descriptive information before saving data to one of the 20 memories makes it easy to keep track of the multiple measurements that make up each WT3 project file.
  • Page 12 All manuals and user guides at all-guides.com...
  • Page 13 This may result in erratic measurements until the system stabilizes again (this can take up to 90 seconds). Remember, never connect the WT3 to a speaker that is connected to any other equipment or damage to the WT3 unit could result.
  • Page 14 All manuals and user guides at all-guides.com Removing WT3 from your Computer You can easily remove WT3 from your computer’s hard drive if needed. Go to the control panel and double click on the “Add/Remove Programs” icon • When the Add/Remove dialog appears, locate WT3 in the list •...
  • Page 15 Save (Ctrl+S) Saves a WT3 project file to disc with the .wt3 filename extension. A single .wt3 file can contain up to 20 memories of data and notes in addition to the immediate data and notes on the Workbench. Project files also contain complete test setup information so that opening a saved project file restores the test setup that was in place when the project file was saved.
  • Page 16 Phase” with the frequency, impedance and phase data separated by a tab or spaces. When the file is opened the data is imported to the WT3 Workbench, interpolated via a powerful cubic spline routine and then plotted on the screen. Note that imported phase data must be in degrees. A minimum of two data points are required.
  • Page 17 All manuals and user guides at all-guides.com Recent Files... A list of recently used files is displayed for easy access. Exit (Ctrl+Q) Exits the application. The keyboard shortcut is very convenient.
  • Page 18 When you save a driver file the complete set of data is saved to a .dvr file which can be opened by the popular loudspeaker design program WinSpeakerz. Similarly, individual driver files saved by WinSpeakerz can be opened in WT3.
  • Page 19 All manuals and user guides at all-guides.com Preferences This command opens the Preferences Dialog (shown below) where you can change various printing, measurement and display settings Plots can be switched between fine and bold lines separately for display and printing. You can select metric units separately for Volumes and other units.
  • Page 20 All manuals and user guides at all-guides.com View Menu The commands under the View menu are as follows: Toolbar Select the Toolbar command to alternately hide or show the toolbar. Status Bar Select the Status Bar command to alternately hide or show the status bar at the bottom of the main page.
  • Page 21 20 memories before proceeding with another measurement. All data in the 20 memories is saved with the WT3 project file. Multiple memories can be overlaid to allow for easy comparison of various measurements. Use the memory buttons in the Toolbar to show or hide various memories. After a memory has been recalled it can then be saved to a different memory.
  • Page 22 Use an added mass that will shift the F(s) lower by about 25-50%. An added mass equal to the driver's Mms is just about right. WT3 will warn you if the shift in the measured F(s) is not within the above recommended range.
  • Page 23 Driver parameters will be cleared to prevent any confusion. Impedance Calibration... When first installed, WT3 is calibrated to within about 2% for the impedance range under 100 Ohms. This is adequate for measuring driver parameters. For even finer calibration you can use this command to custom calibrate the system for your particular WT3 hardware unit.
  • Page 24 When the software is first installed the default test lead impedance is 0.3 Ohms which is typical of the units. Use this command to refine the test lead calibration for your WT3 unit. Shown below is the test leads calibration dialog. Just short the test leads and click OK. The software will measure the test lead resistance and adjust the internal calibration.
  • Page 25 The commands under the Help menu are as follows: Help Topics The complete WT3 User’s Guide can be found under the Help menu > Help Topics. User Information Enter your personal information in this window. This is the information that will display at the Splash Screen and in the title block of your printed reports.
  • Page 26 Raise the Windows volume control to maximum. • Click the "Measure Free Air Parameters" button at the left side of the WT3 screen. • You should hear the sweep from the speaker, the impedance is plotted and the parameters are •...
  • Page 27 A typical sealed back moving coil tweeter operates as a very small closed box system and therefore can be characterized by it's closed box resonance and Q, F(sc) and Q(tc). You can use WT3 to measure both of these parameters for tweeters as well as woofers and midranges. The frequency response of a tweeter is the same as that of a purely electrical second order high-pass filter with the same electrical resonance frequency and Q as the tweeter's electro-acoustic resonance and Q.
  • Page 28 All manuals and user guides at all-guides.com Here is a typical result when measuring a tweeter: We can read the tweeter's resonance frequency, F(s) (or, more strictly F(sc)), directly from the impedance plot or note the value at the Measured Parameters F(s) field. Just as with a closed box, the system's Q(tc) is read from the Q(ts) field.
  • Page 29 All manuals and user guides at all-guides.com Using WT3 to Measure a Resistor Before starting, make sure the WT3 unit has been calibrated and has stabilized for at least 90 seconds. Measure the value of a resistor as follows: Launch the WT3 software and make sure the volume is set at maximum.
  • Page 30 All manuals and user guides at all-guides.com at 0 degrees except for a slight rise at the high frequency limit. Here the measured value of 9.998 Ohms is seen to closely match the resistor's specified value of 10 Ohms +/- 0.1%. At full playback volume the "noise"...
  • Page 31 All manuals and user guides at all-guides.com Using WT3 to Measure an Inductor Before starting, make sure the WT3 unit has been calibrated and has stabilized for at least 90 seconds. Measure the value of an inductor as follows: Launch the WT3 software and make sure the volume is set at maximum.
  • Page 32 1.0 mH rating. At 0.2422 Ohms the inductor's DC resistance is nicely low as required for use in a passive crossover. Note that WT3 can measure inductance at either 1kHz or 10 kHz based on the selection at the Preferences dialog. Measurement at 1 kHz is recommended for general use except when measuring inductors less than 0.5 mH or drivers...
  • Page 33 A closed box type of loudspeaker system is characterized by a resonance frequency F(sc), an electrical Q value Q(ec), a mechanical Q value Q(mc) and a total Q value Q(tc). Just as you can use WT3 to measure a driver's parameters you can also use WT3 to measure the corresponding parameters of a closed box loudspeaker system.
  • Page 34 All manuals and user guides at all-guides.com Here is a typical result when measuring a single full range driver in a closed box type enclosure: By inspecting the impedance plot we can determine that this is a closed box type of loudspeaker system from the presence of the single impedance peak in the low frequency range.
  • Page 35 The enclosure's tuning frequency is indicated by the frequency where the impedance is a minimum between the resonance two peaks. Before starting, make sure the WT3 unit has been calibrated and has stabilized for at least 90 seconds. Measure the system impedance as follows: Launch the WT3 software and make sure the volume is at maximum.
  • Page 36 All manuals and user guides at all-guides.com Here is a typical result when measuring a single full range driver in a vented box type enclosure:...
  • Page 37 All manuals and user guides at all-guides.com In order to read the vent tuning frequency, F(b), more precisely we can adjust the frequency display limits to zoom in on the frequency range containing the two impedance peaks as shown below: At this screen we can determine that F(b), the tuning frequency of the vented box, is approximately 40 Hz by locating the impedance minimum between the two peaks and reading the frequency where the minimum occurs.
  • Page 38 The enclosure tuning frequency is the frequency between the two peaks where the impedance is a minimum. Before starting, make sure the WT3 unit has been calibrated and has stabilized for at least 90 seconds. Measure the speaker system impedance as follows: Launch the WT3 software and make sure the volume is at maximum.
  • Page 39 All manuals and user guides at all-guides.com Here is a typical result when measuring a complete 2-way speaker system: We can see that this system employs a vented woofer system with the vented enclosure tuned to about 40 Hz. Even with a minimum impedance of just over 6 Ohms this would often be considered to be a nominal 8 Ohm loudspeaker system.
  • Page 40 All manuals and user guides at all-guides.com Using WT3 to Diagnose Loudspeaker Fault Conditions When carefully applied WT3 can be used to spot common problems with a speaker system. For example, the screen below shows two impedance measurements of the same two-way speaker system.
  • Page 41 All manuals and user guides at all-guides.com In the screen below you see the same system as above but this time with a shorted tweeter. The green (upper) plot again shows the normal impedance response of this system. The yellow (lower) plot shows the system with a shorted tweeter.
  • Page 42 All manuals and user guides at all-guides.com Now let's examine similar fault conditions for the woofer. The screen below shows the same 2-way system as above with the green plot representing the normal system and the orange plot showing the system in a fault mode with an open circuit woofer.
  • Page 43 All manuals and user guides at all-guides.com Finally, here is a screen shot showing the same system with the woofer in a short circuit fault condition (lower blue trace). As we see in these examples often a system fault is most easily detected by comparing the suspect system to a known good system.
  • Page 44 The resistor is normally selected to match the nominal impedance of the system. The capacitor value can then be calculated or, in this case, determined empirically. Because WT3 is able to perform impedance sweeps in just a few seconds it can be used for any type of repetitive adjust and measure process...such as designing a Zobel network to neutralize the inductance of a driver.
  • Page 45 All manuals and user guides at all-guides.com we can get it in the upper frequency range. Let's start with around 1 uF for the capacitor and see what we get for a new impedance response. The screen below shows the new impedance response in purple with the original (uncompensated) response in blue.
  • Page 46 All manuals and user guides at all-guides.com Below is the impedance with the capacitor increased to 2 uF (blue trace). The original (uncompensated) impedance is shown in green. The 2 uF capacitor has flattened out the impedance so that it rises only slightly above 8 Ohms. Since it is easy to do let's continue to increase the capacitor value and see if we can get a further improvement.
  • Page 47 All manuals and user guides at all-guides.com The screen below shows the effect of increasing the capacitor to 3 uF (blue trace). The increase from 2 to 3 uF gave even further improvement as the impedance above resonance is now quite flat. Just to see what happens, let's increase the capacitor further to 5 uF.
  • Page 48 Zobel connected. In general you could take the same approach to verify other networks such as the resonance compensation network (R-L-C) sometimes used to neutralize the impedance peak of a tweeter. As an impedance measurement system the additional applications for WT3 are limited only by the user's imagination.