Why YOU need to use DATS v3 for your audio builds
I got asked several times after posting the DATS v3 JW Module results on social media to run through how i use the system, How to interpret it and how you can use that information to then take into modelling software to design an enclosure using accurate TS parameters,
Having to rely on the manufacturers TS Parameters can sometimes be hit or miss, Its impossible to tell if drivers have been run in before testing, what method was used to determine parameters, hardly anyone makes it easy! Are the numbers averaged across the production run? What frequency does QC (Quality control) occur? Is it one per batch of 10? 100? 100,000? Where they tested in neutral atmospheric conditions? Are they even trying to be honest? Do they make it simple for the starter enthusiast by stating if a dual voice coil drivers have been tested in series, parallel or single coil configurations?
I cant say how many times in the past i have had to dig relentlessly, eMail companies to be ignored just to get a full workable set of TS Parameters. The worst seems to come from manufacturers who rely on low quality control practices from the far east. Cheap driver manufacturing generaly means that tolerances between drivers can vary widely and the frequency of QC drops dramatically. Buying from these sorts of companies the increases the chances of receiving a varied range of parameters increases especially if buying sporadically or over a long period of time.
One of the costs in driver manufacturing is tolerances. The tighter the tolerances there greater the chance of all the drivers in a production run to be closer matched this increases cost per run as the machines have to be setup precisely and tested this takes time and money. Another one to consider is Quality Control, how many drivers in a batch get tested can make a big difference, Automation techniques here can cut costs but is just added back for the access to the technology.
Having the Dayton Audio Dats V3 in your arsenal of tools takes away all the guess work and provides you with an accurate set of data points to work from, No longer do you have to worry about relying on the manufacturers data sheets, You can just generate your own for not alot of money!
Lets take a look at the software and how to use it
Lets skip whats Already covered!
Dayton Audio have a great start up guide on using the DATS Hardware which runs you through the setup procedure of calibrating the test leads and zeroing the system via the 1kOhm calibration terminals on the front panel, It also covers how to do a simple impedance test of a speaker but not much else. I feel that this is a bit of a letdown in terms of use. I think that since this is marketed to diy enthusiasts it should come with a little more in depth instructions and information.
How DATS v3 works out the TS Parameters is by sending a sinewave sweep across the frequency spectrum and working out the impendace of the driver, It then uses a derivative of the Thiele Small free air constant current methodology to calculate the rest of the remaining TSP’s
Its important to note that the most widely accepted and common method of using DATS is the “Test box method” which can be selected in the top right hand corner of the software window whilst using the “added mass method” to the cone does work it must be done right. Building a test enclosure is cheap, quick and best of all repeatable EASILY.
Adding mass requires having multiple sized calibrated weights for being able to test between small and large drivers, Unlike having the need for just two or three test boxes. They need to be from quality austenitic steel so that they dont rust over years of use which would change the weight over time. The cost and difficulty just doesnt justify the method for the average builder.
Make yourself a Reusable DATS test enclosure
Its important to make a long lasting test box that you can use over a long period of time it ensures continuity across your projects and gives you a sense of confidence in the results. I made this a while back for testing drivers under 6″ its as close as you can get to 0.2 cuft as possible, Its braced heavily across the bottom panel to minimise panel resonance and lined with dampening material to aid with reducing internal reflections.
The Importance of Learning the Software
One thing im in two minds about is how the software displays driver data. The DATS system can analyze and collect much more than it displays on the main user interface.
To access the whole set of TS Parameters you need to enter the Driver Editor, Slightly hidden under the Edit Menu (shortcut CTRL + D) it open this window which shows additional key information like BL Product, Min/Max Impedance etc.
It also allows like many software programs to enter various physical dimentions of the driver, Reproducing old designs means you dont need driver or documentation at hand, absolutely great!
Building up a driver database that you can reference back to is incredibly important, I also do this with all my enclosure designs in Bass Box Pro, WinISD and HornResponse.
It really can be a massive tool in your arsenal, Having previous projects to refrence from means you can make nudges to guess work in the right direction, its a great way to build experie ce over time without having to document or remember every detail in the build.
Generator and Oscilloscope Functions
The Oscilloscope if youve never had acess to the oldschool desktop ones, Ever had experienced or seen anything like it before it may seem confusing or a counter intuative tool to provide in the DATS system.
Understanding the Impedance Graph
What are we actualy lookint at? Firstly lets focus on the BLUE trace, This is one of the critical components of sound system design and represents the impedance of the driver and how it changes over the spectrum. Understanding this is key to efficiency, its literaly telling you how much work an amplifier is going to have to do to drive that speaker at that particular frequency.
You will always have a spike in impedance at the Free Air Resonance of the driver and a rising trend as frequency increases due to the inductance of the coil.
If you think of it this way, high frequencies require less cone movement and energy to produce equal SPL so an amplifier will not struggle producing power at these high impedances and fast oscilations even though inductance rises its the lower frequencies that take up vast amounts of energy to produce the same SPL.
Now you may question why does the impedance rise at FS? Think about it, if high impedance relates loosely to cone movement when the cone reaches its resonant peak or “free air resonance (FS)” its basicaly not moving at all and producing maximum spl at its most efficient frequency.
This is all critical information before even desinging an enclosure, You can already have a general grasp of how much power and headroom you need to balance and drive the speaker
Lets put this into simple terms, very unrealistic terms but it conveys the right idea,
Phase equates down to the relationship between Voltage and Amperage in an amplifier let me explain!
Lets focus now on the DATS v3 RED trace, this is the phase response and cant be simply understood without understanding some electrical engineering. The simplest way i can explain this is if you were to use a garden hose and turn off the nozzle, disconnec it from the outlet and try to blow the water out in pulses, There would be a clear delay or “lag” in the water spewing out the other end this is called current lag.
Lets relate this to a speaker. If your amplfier is not in electrical phase it will have to work harder to keep the speaker moving in harmony with the input signal, The amplifier will start to lag or lead, Create more heat and use more current, If the amp is already at or near its limits theres no thermal or electrical headroom to compensate for this and things start going south! This has nothing to do with clipping!
Check this diagram out it should make sense, think of the RED line is the input voltage (you blowing into the hose) and the GREEN as the lag behind in current.
This is the phase shift between current and voltage, The voltage waveform is no longer in phase with peak current output so there is an internal lead or lag in the amplifer.
The relationship between negative and postive phase shift determins whethere the amplifier will be working in a resistive (postive) or capacitive (negative) circuit Ie: lead or lag behind eachother.
At 45 degrees, probably a speakers worst case scenario the output transistors will have to dissipate twice the amount of heat and produce half the amount of effective power with of course twice the amount of current consumption.
Lets examine the Spectrum Analysis of a 40hz Square wave impulse with a 5ms attack 80ms sustain and a <1000ms release. Using a synthesizer called Phaseplant from Kilohearts its possible to shift the phase of one oscilator by upto 180 degrees bilaterally to simulate and give you a visual representation.
The image to the left is the clean signal The right image is the signal phase shifted 45 degrees.
If you look closely between the first and second picture notice the osciloscope overlay in the background, Its easy to see the inital attack move in a positive phase intact but the shift has caused a change in the shape of the square wave as it travels back and crosses over to the negative side of its oscillation.
Closely examine the Green Spectrograph too, you can clearly see the shift how it blurs and its effects.
In this experiment i have shifted the phase by -45 degrees to simulate this loss in efficiency. Keep in mind that this isnt taking into fact any real world factors, its just a good visual example to understand the theory.
You can see theres a 1.4db loss in acoustical energy available just by shifting the phase in this signal in a production environment where there’s a non lossy environment.
The dip in perceived loudness comes from the lack of transient continuity in the shifted signal, its blurred and washed out. The first image shows how weve gain matched this signal to 0db, Once we shift the signal 45 degrees you can clearly see theres a percieved drop in loudness.
As we now have learnt speakers have a rise in impedance at its resonant peak, Simply we can make the conclusion that due to impedance each side of the driver’s free air resonance becomes harder to drive for an amplifier. The cone starts to move more and more as frequency shifts away from FS meaning an amplifier has to drive the cone forward and backwards alot more than at FS. More work means more power!
Designing an enclosure from this now starts to become a balancing act between many many factors. The more factors you calculate the more complex the simulation becomes, The more complex it becomes the more errors could be introduced and thats where experience come in to play. The point where you stop going round in small circles looking for that little bit more spl or bandwidth for example can be a long or short process depending on your experience.
Having a Dayton Audio DATS test system at your disposal can really aid in understanding a driver fully before having to assemble and test anything.
After owning the V2 and now having the Dats V3 for a while I can say its an invaluable tool of the trade and I’d never be able to achieve my designs without it, Being able to get real world hands on parameters means I can track things like break in times and how the driver loosens up, what changes and how you can maximise on these differences.
I would HIGHLY recommend a Dayton Audio Dats system.
