WT3 Woofer Tester Review - Dayton Audio

Filed under: Home Audio > Measurement Devices & Software


- Image: Parts Express

Intro
I received a very fun toy in the mail from Parts Express that was on back order for a while. Maybe you've heard of it? It's the Dayton Audio WT3, a "Woofer Tester" designed to accurately measure thiele/small parameters in seconds. If it sounds at all familiar to you, you've probably seen the ramp-up advertising from PartsExpress or you're familiar with the original Woofer Tester that PE used to sell from Smith and Larson Audio. There has been a lot of interest in the new Dayton WT3 Woofer Tester, so we thought a full review would be appropriate.


- Image: Parts Express

Looking at the WT3 on the PE website, there is a lot of focus on how easy, fast, and accurate the measurements are (see above image). The aim is clearly at DIY enthusiasts of varying backgrounds. The measurement of thiele/small parameters is critical for those who like to Do It Yourself as it allows a user to accurately simulate an end-product before they've cut a piece of wood. Scroll to the end if you just want my final conclusion.

Setup
When I opened the package, I found a calibration resistor included (labeled as 10k ohm), the cables to connect the speaker to your computer for measurements (alligator clips for the speaker end, USB for the computer end), an installation CD and a "Quick Start" for the WT3. It's all pretty straight forward.


- Image: Parts Express

Starting with the installation of the software, it is a pretty easy go. You throw in the CD, navigate the CD drive and double click the setup file. A couple quick clicks and the software was installed. Pretty painless, but I was a little surprised by one thing: no autorun install. Nowadays, it is pretty much standard to have the CD launch into install/setup when first inserted and this software doesn't. Finding setup.exe is easy, but I expected a little better. That's no big deal, though.

Once installed, you can connect the WT3 to your USB port. A blue LED power indicator will come on the WT3, which is a nice touch. The steps recommend that you set your windows volume control to maximum, which is easily done (and documented well enough). The Quick Start walks you through calibration using the calibration resistor and indicates that you can calibrate the test leads as well. Just a note: you absolutely must perform calibration with the resistor AND calibrate the test leads. The test leads appear to have surprisingly high inductance that requires you calibrate for accurate impedance measurements. But before that, wait a couple of minutes. The Quick Start makes a point of mentioning that you must wait at least 90 seconds to allow the WT3 power supplies to stabilize, and this is very critical. If you attempt any measurements immediately, you'll find your results to be less than favorable. This is a bit of an inconvenience, but certainly not that big of a deal. If you can't wait 90 seconds, well... speaker testing probably isn't for you.

Once impedance and test lead calibration is completed, you can proceed with your testing. The Quick Start is very clear about one thing: absolutely do not test these speakers when connected to an amplifier or external power source!

Measurement Accuracy
The WT3 boasts that it takes 30,000 data points in a few seconds using a "new swept sine wave technique." During the measurement process, I didn't notice anything abnormal about the audible sine wave. When I called PE to ask more, no one really had any more information on it so I can only guess. But whatever the technique, the WT3 is accurate enough. Compared to measurements made in Speaker WorkShop and Sample Champion, measured thiele/small parameters are usually within what I would consider acceptable tolerances: 1-5%. The accuracy of the measurement still has some dependence on the end-user, though.

Points of Satisfaction
I would say that I was pretty satisfied with the accuracy and precision of the thiele/small measurements made by the WT3, although I did encounter some problems measuring Le. The WT3 is also fairly intuitive and very quick to measure with. The footprint of this tool is also extremely small, which is something I can't say for most other measurement setups I have used. The instructions that are provided are fairly straight forward. I think any average Joe could pick up a WT3 and have results very quickly. And there is more than enough room (in my opinion) for these results to be stored in the 20 memory slots per project available. And these measurements can be easily exported to .txt or .zma for use in other programs.

Points of Concern
In terms of simplicity, the WT3 is a champion, no doubt about that. But I do have concerns about the conclusions a user could draw from its use. For example, the WT3 is very sensitive to drive level. This is shown through the sensitivity to the volume settings in Windows and to the initial stabilization period. The steps suggest the use of a 1k Ohm calibration resistor, which is acceptable (and can also be changed if you choose to do so), but it merely suggests calibrating the leads. I think I've said this once already: YOU MUST CALIBRATE THE TEST LEADS!

The measuring of a driver's Vas proves to be a bit problematic as well. In cases where I experienced a larger difference between one measured set and another, I could usually track this down to a problem with the Vas measurement that was made. The cause? Well, the three preferred methods (Test Box, Added Mass, and Specified SPL) are what pose a problem. The Test Box Method requires a near exact measurement of volume in an enclosure with no leaks. The Added Mass Method requires a mass be added to the driver that will not shift when excited, should not be susceptible to a magnetic field, and must fall within a certain window of mass depending on the originally verified mass. The Specified SPL method requires an accurate measurement of the SPL. To make matters worse, the user guide does not specify which of the methods is preferable. And with poor Vas measurements comes problems with the other measurements as well (like efficiency, for example).

Conclusion
Overall, I would say that the WT3 is a good product. Lukas kindly pointed out that there isn't much for competition within the same price range (the notable exception being the free Speaker WorkShop paired with a Wallin Jig or Claudio Negro's Cable Jig, but this requires a larger investment of time). And for ease of use and general accuracy, the WT3 is a good option for many enthusiasts at $99.

The main downfall of the WT3 is the gap between providing easy results and understanding the results you have. It is important to be able to understand what you're looking at in the event you get an unanticipated result... before you run to a forum saying that "Company X published false t/s parameters!"

My end recommendation is a buy, however, because I think most users will be very satisfied with the ease of use the WT3 offers. And the reviews on the PE site show that most have been very happy. I noticed a couple unhappy reviews with complaints that I would consider to be unwarranted, mostly citing a lack of measured t/s parameters which can be found in the Driver Editor dialog box.

If you want to supplement the WT3 with a book that will keep you informed, I will recommend the same thing I always do: Buy Joe D'Appolito's book, Testing Loudspeakers.

Screenshots (click on the thumbnails for a larger image)


Snapshot of the main window of the program.



Driver Editor dialog box; all fields are generated by either measurement or manual entry.



Shot of four measurements; you can see the four memory slots used up near the top.



- Note 1: This device was paid for in full by Audio Junkies. We did not receive anything for this review and neither Parts Express or Dayton Audio is associated in any way with Audio Junkies through advertising or any other means.

- Note 2: Audio Junkies does not typically do product reviews. I felt that there was not enough information out there on this device though, so we made an exception. -Lukas