Electrical performance is captured by a whole other type of testing. These days, I use Dayton Audio’s DATS V3 measurement system to test the electrical load of a loudspeaker: electrical impedance and phase. Before that, I used a circuit I made using a 100-ohm resistor and Room EQ Wizard. That method worked, but it was a bit more involved and had more steps than just using the DATS V3 analyzer. However, one thing that neither method is able to capture is how the speaker reacts at higher drive levels. That can be important, especially for those who enjoy “spirited” listening levels.

Enter Dayton Audio’s new DATS LA Loudspeaker Analyzer. It has a built-in 100-watt amplifier that can be used to test loudspeakers over a wide range of signal levels, but it can do a lot more than just that. It can capture Thiele/Small parameters easily. It can check drivers for alignment problems that cause “buzz and rub” issues. It can measure the electrical properties of insulators, capacitors, and resistors — the components that make up a crossover circuit. And what really intrigues me is that Dayton Audio claims it can measure driver motor and suspension symmetry. Previously, that sort of loudspeaker analysis had to be done with Klippel Analyzer systems, which use lasers and cost many tens of thousands of dollars, so if Dayton Audio has found a way to do it with a $700 system, that is great news for anyone who wants to get into the loudspeaker measuring game but doesn’t have the money or space for a Klippel system.

So how well does it work? Let’s now dig in to find out…

DATS LA: What You Get

The base DATS LA unit is not huge, at about 2 inches high, 6 inches wide, and 11 inches deep. Included in the package is a USB cable, a short 3-foot power cable, and test leads. There is also some mounting hardware for those who have a fixed place in mind. The DATS LA unit is a substantial aluminum piece that seems well-made. 

Much of the technology of the DATS LA system is driven by the software, and, thankfully, the software is easy and intuitive to use. Users will need a computer running a Windows operating system to run the DATS LA application software. The DATS LA application software can be downloaded from the DATS LA product page at Dayton Audio’s website or through the product page at the Parts Express website.

Once the software is downloaded and installed, setting up the system is very easy: just plug in the DATS LA unit to your computer via the USB cord and launch the software. There are a couple of calibration tests that have to be run, but they only take a few moments. It does pay to go through the product manual, especially for those who do not have experience with previous DATS systems from Dayton Audio, but those who have will find the basics pretty familiar.

Using the DATS LA

Operation of the DATS LA system is fairly easy, depending on what you want to test. Testing for VAS values may require a bit of preparation if the user is not certain of M(ms) or sensitivity specs of the driver. After running through the calibration routines, just hook the driver terminals up to the DATS LA posts, and select the tests that you wish to run. For impedance testing, it helps to perform that in a quiet environment for accurate results.

Testing for VAS within the T/S parameters (Thiele/Small parameters) does require a bit more than merely hooking up the DATS LA to the speakers and initiating the test in software. VAS is the measure of the volume of air that has the same acoustic compliance as the driver suspension. It is basically how springy or compliant the driver’s suspension is. It is needed to know the ideal size of the loudspeaker enclosure, with high VAS values indicating drivers better suited for larger enclosures and smaller VAS values suited for smaller enclosures. The DATS LA system can accommodate four different methods of measuring VAS. One method requires inputting the sensitivity spec in the testing software. Another method requires entering in the M(md) specification in the testing software, where M(md) is the moving mass of the driver. The problem with these two methods is that these real specs can vary widely from the manufacturer’s claimed spec and so can be less accurate.

The two other methods will provide more accuracy but are more involved. The “test box” method requires the user to build a sealed enclosure to mount the driver in, which is, of course, a bit of a project. The “added mass” requires the user to add a known mass to the cone and input the mass in the testing software. The mass must adhere to the cone and not move during excursion. I tried this method by using Dayton Audio’s DMK-1 Delta Mass Scale and Weight Kit. It comes with museum putty and a scale so that users can stick a precise amount of known mass to the cone without leaving residue. A couple of tips for getting better results from the DATS LA: firmly clamp the driver by the frame so that it doesn’t move during testing, and also make sure the backplate vent is not blocked if the driver has a ventilated pole piece.

DATS LA Test Results

I tested the DATS LA system on a myriad of drivers I had on hand. Many of them were drivers from speakers that were made for completed loudspeakers and thus did not have any data available for them. However, one retail driver I tested the system on was the Dayton Signature SIG180-4 6.5, a low-cost 6.5-inch woofer. This is a nearly ideal driver for the DATS LA system because the 100-watt amplifier should be enough to push it past its linear limits without putting it in danger. Here are just a few of my results (the DATS LA system produces a lot of data):

The above graph measures the BL(x) of the Dayton Signature driver. BL is basically how much magnetic force is used to move the woofer, and it is sometimes called the “force factor.” B is the strength of the permanent magnet, and L is the length of the voice coil wire. BL is measured in Tesla-meters. In almost all drivers, BL is the strongest where the woofer is centered in the gap at or near its rest position. In this position, the coil mass has most of its proximity to the permanent magnet field. As the voice coil moves, its electromagnetic field is pushed away from the peak of the permanent magnetic field, so the magnetic force applied to the driver lessens. This is shown where the curves roll off moving from left or right of center, since center is the rest position and the Y-axis is the strength of the coil’s fields plus the magnet’s field.

The above graph measures the frequency of the driver’s free-air resonance throughout the driver’s excursion. The free air resonance is the frequency at which the driver’s moving mass oscillates most easily in free air, or, to put it another way, the frequency at which the least amount of energy is needed to vibrate the driver’s moving mass unencumbered by an enclosure. As we can see from the above graph, the Dayton Signature driver does shift its free air resonance upward in frequency as the driver moves away from its rest position. All drivers do this, so this isn’t an unusual result on the Signature’s part.

The above graph measures the Dayton Signature driver’s Kms(x), which is a measure of the suspension’s stiffness throughout the cone’s excursion. At its rest position, the suspension will be at its loosest, but as the moving assembly is pushed further away from the rest position, tension is added to the suspension, thereby making it stiffer. The Dayton Signature driver looks like it doesn’t become highly stiff until about 5mm of excursion.

The above graph is a measurement of the Le(x) of the driver throughout its excursion. The Le is how much inductance the coil generates, or how much back EMF the AC signal produces by interacting with the coil, and it is measured in millihenries (mH). Inductance reduces the bandwidth of the driver and also generates distortion since it acts in opposition to the applied source voltage. High-fidelity drivers strive to reduce inductance as much as possible. The values that we see above from the Dayton Signature driver hover around 0.33 mH to 0.43 mH, a nicely low level of inductance, which will help this driver have a wide bandwidth and low distortion.

The above graph shows how the impedance and phase of the Dayton Signature driver shift as the current increases. Although many loudspeaker driver graphs show impedance and phase as single curves, the reality is that they don’t stay that way for different drive levels. The electrical characteristics of a driver change, as can be seen above, and the DATS LA makes it easy to see these changes as well as many other parameters that change over differing drive levels. It can be seen that the impedance and phase do not shift a whole heck of a lot for the different drive levels tested here. The DATS LA system allows the user to set the amplitude range and number of test sweeps for this testing, so users have a lot of flexibility here.

The above table compares the parameters of the driver from the manufacturer’s spec to the values obtained by the DATS LA system using the “added weight” method of measuring. The values are not far off except for the M(ms) value. I think the M(ms) value is a bit off because the “added weight” method makes that particular value a bit tricky to gauge. When I tried the specified M(md) method, I came a lot closer to the manufacturer’s spec, although the other values were farther from spec. The manufacturer’s F(s) spec is a bit lower, but that is a value that can be affected by “break-in.” F(s) will fall a bit after the driver has seen some use.

Because these drivers are not likely to be built to extremely tight tolerance levels, there is bound to be some variation among individual samples, and so we cannot assume that the manufacturer’s specs are more accurate than the DATS LA results. The levels of QC needed to ensure every single driver matches the stated specs exactly would make the driver prohibitively expensive. What matters is that the driver behaves predictably enough in an enclosure. This driver has also been tested by loudspeaker maestro Vance Dicakson at AudioExpress, and his test results are closer to what I measured with the DATS LA than the manufacturer’s specs. The DATS LA system seems to get the job done.

DATS LA Conclusion

The DATS LA system will not appeal to the masses, but it can be a valuable tool for loudspeaker designers, manufacturer QC testing, and enthusiasts. It’s an affordable way to measure loudspeaker parameters, unlike many other systems that cost many thousands of dollars. Loudspeaker designers and engineers can use it to determine driver parameters or double-check manufacturer specs. Manufacturers can use it to quickly and easily check if drivers are being made within acceptable tolerances. It’s also handy for manufacturers to check for misalignment via the “buzz and rub” function. And enthusiasts such as myself can get a better look at the attributes of drivers and how drivers compare to each other.

The DATS LA system will certainly be a godsend to prospective manufacturers and designers who want to try their hand at loudspeaker design but don’t want to commit the fortune it costs to outfit a lab with pricey and bulky test equipment. It does an awful lot in a small, easy-to-use, and affordable unit. The learning curve is not high at all, although I can see users getting better results with continued experimentation and refining of their testing method. I ended up learning a lot about some “mystery” drivers that I had lying around, and if you are a speaker enthusiast like me, I am sure you might have a box or two of drivers that look potentially useful but are unknown quantities. For people like me, the DATS LA system can save these drivers, because not many people would want to spend resources and time constructing a speaker system around drivers with unknown parameters.

Dayton Audio’s DATS LA is a nifty tool that will certainly become a must-have for amateur speaker designers in the coming years. I am excited to see what the loudspeaker community will learn from using this system in the future, and I look forward to the interesting discussions that it will spark. The information it will yield will surely help to turn middling designs into good ones and good designs into great ones.