Woofer Tester II

[4313B]

This was posted on another forum.

http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=390-802&raid=25&rak=390-802

If anyone orders one let us know how you like it.

[Mr. Widget]

If anyone gets one in the SF Bay Area, I would be interested in comparing it's results to those from using Clio.

Widget

[spkrman57]

I have the original and it is a great bargain for use at home.

Ron

[4313B]

Just happened on this today -

BassBox 6 Pro Changes
Version 6.0.20 changes (29-Mar-05):

A new import filter was added for the Woofer Tester II. It can import the measured Thiele-Small parameters from "log" files created with the "Export to BassBox" command in the Woofer Tester II's File menu.




X•over 3 Pro Changes
Version 3.0.15 changes (11-Apr-05):

Removed the driver polarity from the impedance net plot line calculations when the phase is included. This is because the driver polarity does not affect the impedance presented to the amplifier.


Version 3.0.15 changes (29-Mar-05):

A new import filter was added for the Woofer Tester II. It can import the measured Thiele-Small parameters from "log" files created with the "Export to BassBox" command in the Woofer Tester II's File menu. The new Woofer Tester II can measure both open and sealed back drivers (woofers and tweeters) and the import filter allows data to be imported for any driver (woofer, midrange or tweeter).
A new feature was added to the System Impedance graph. The user can now control whether the net impedance plot line is summed with or without the phase in similar fashion as the net amplitude response plot line. The feature is controlled with a new net impedance "ø" (phase) checkbox on the "Graph" tab of the Preferences window.
The calculation of the band-pass filter of a 3rd-order 3-way crossover network was tweaked to provide a better response on the low-pass side of the band-pass filter.
Could be fun I suppose.

[johnaec]

Dang it! I just recently got BBP6 and XO3 and now you're gonna' make me go out and get sumpin' else... :biting:

John

[4313B]

Yeah. It's cheaper than the orginal Tester was though and supposedly considerably better. The only thing left to get would be an RTA to check real world results. Gotta love being able to run all this crap automagically. I think Robh3606 already has BB6P and an RTA ;)

Other uses which might not be so obvious would be inductor triming and quick measurement of enclosure tuning frequencies. The USB hookup makes it easy to use with laptops on the go.

I went ahead and ordered one to play with.

[Robh3606]

I think Robh3606 already has BB6P and an RTA http://audioheritage.csdco.com/vbulletin/images/smilies/wink.gif

Your right I am curious to see what you think.

Rob:)

[johnaec]

The only thing left to get would be an RTA to check real world results.'Already got one in the DBX DR260 - calibrated mic also...


The USB hookup makes it easy to use with laptops on the go.That sounds kool! The laptop can control the DR260 via serial port, so that leaves the USB open...

Let us know your impression when it arrives!

John

[spkrman57]

Hell, I paid just a little over $300.00 when they first came out. SOunds like a bargain.
ROn

[Zilch]

So, it'll generate the impedance curves for various compression driver/horn combinations we need for crossover tweaking?

Ordered.... :p

[4313B]

What do you think so far Zilch?

[Zilch]

What do you think so far Zilch?It was up and running in minutes. After quick calibration, it generated definitive information on Fs of old vs. refoamed LE14A's (10 minutes of testing), easily confirming standard advice on the subject from this forum.

Instructions are "sparse" (meaning a quick read), and I had to play with the parameters a bit before I became comfortable with what was going on. The format and content of the various export options remains unclear.

I'm still a bit uneasy about letting it sweep compression drivers at low frequencies, but the testing currents are so low (3 mA) that I have little basis for concern, apparently.

It's generating beaucoup useful info here, and lotsa cool plots, too.

Gonna test some box tunings next, and I need to get a roll of nickels for mass loading woofers. Instructions inform you fully about about that part.... :p

User Manual here: http://www.parts-express.com/pdf/390-802m.pdf

[spkrman57]

I will pass my old one off to one of my friends and have to buy the new one and since I will have a new computer(this one is dying slowly), I can buy the BB6 and other software to get a new software package altogether.

Ron

[Zilch]

http://www.woofertester.com/

[spkrman57]

After some e-mail exchange with WTPRO(helpful forum memeber here), I finally figured out why my WT2 would not work correctly and thought I would pass it on here for others like myself who are not pc wizards.

I originally could not get the calibration or Qtc/etc tests to run no matter what I did, after some e-mails with WTPRO, I found out that when using a "USB" that my pc would default audio to the WT2, after I changed the audio(sound devices/etc) to default to the pc's sound card, I was able to move on.

I still am not proficent in its use like the old woofer tester(a dinasour like myself), but with more use I am getting better.

So if your audio defaults to the WT2, change the default to the sound card in your pc, and things should work just fine!

Ron

[spkrman57]

From helpful e-mail from forum member (WTPRO), I found out you have to be sure the audio/sound for your pc does not default to the WT2, if it does, change the audio/sound default to the sound card in your pc.



Many thanks to "WTPRO" who gave me the info I could not find elsewhere!!!

Ron

:applaud: :applaud: :applaud:

[WTPRO]

Good Morning All

I just thought I would mention that as questions come in, Brian and I (the other woofer tester guy) are adding those answers to the www.woofertester.com (http://www.woofertester.com) FAQ page. The FAQ is not too flashy at this point, but hopefully this will change soon.

Another tip is that another test code version will probably post soon. For example, and Giskard may want to chime in as it was him that wanted to know if the WT could generate an accurate TS model for a mid or tweet, is a new method (still under consideration) that will back out TS params from an efficiency rating and piston diameter. You may recall the normal method of Vas testing uses a test mass or box. Well, if you dig into the equations you will find that if you know piston size and efficiency, you can generate the other parameters.

Making a 'guess' like this may not be the best option, but for something like a mid or tweet, it more or less works. More importantly, and the original intent of the effort, is to create an electrical model that works with a crossover design package.

Best regards
Keith

[Zilch]

Yo, KEITH!

How come I consistently get negative Le's on compression drivers?

Am I not calibrated correctly or something?

[WTPRO]

Hi Giskard

More than likely the phase of your compression driver is negative at 1Khz. The issue is that the convention for 'Le' has always been to measure at 1Khz. Hm... in this case Le would be more like Ce! This Le convention never was any good IMO.

The *better* solution is to export an ASCII log file and look at the impedance, phase, resistance, inductance and capacitance columns. From this you can figure out what the actual load will be for a particular test frequency.

An even better solution, especially since I know you have the upgraded SW, and if your crossover design SW can handle it, is to use the frequency dependent Rem and Lem series reactance values computed from the parameters Exm, Kxm, Erm and Krm. This goes in series with the mechanical tank circuit.

1) Rem=Krm*(2*pi*f)^Erm
2) Xem=Kxm*(2*pi*f)^Exm
3) Lem=Kxm*(2*pi*f)^(Exm-1)

An electrical equivalent 'tank circuit' for the Fms peak is also given in a message box at the end of the Q/Fs test or when copying the test data into the simulator. Again, this is a new version 1.02 feature. Keep in mind that at the moment the 'tank info' message box only pops up during the test or during a test value to simulator copy. This is because the Ces, Les, Res tank is really only valid for free air Fms, which as far as I can tell is of no practical value since I suppose most people will want to put their driver in a box!

This is where (IMO) the also new to V1.02 simulator comes in handy. The bottom line is that if you tinker with the box volume and tuning you can get the impedance humps to line up with the measured box test or arbitrary sweep values. If you then adjust Rem, which ends up being the same as box loss, you can also get the peak magnitudes to line up. If you then look at the response, you should be pretty close to reality.

This you cant do right now, but assuming this last 'alignment' has gone well, you may still want to modify the box. Therefor it might make sense to export the *simulated* box Z/P so you can work on a crossover *before* committing to a new box. Usefull? If 'Yes' I might just have to consider adding this.

Oh... I almost forgot... that early version of SW that I made specifically for you might be a bit goofy *if* the impedance does not sufficiently rising at the high sweep frequency. You may recall that the new method I added for you was testing the high frequencies first and then backing up to calculate the lows. This gives Lem Rem before the Fs/Q sweep begins. That in turn becomes important when finding the other points in the graph that would have otherwise failed in the old Q/Fs method. As an example, look at the phase of your compression driver at Fms. It may not even fall below 0' degress, which makes it pretty hard to find a zero phase crossing. By backing out Rem/Xem first, this is brought back to a zero reference and the test completes.

Cheers :rockon1:,
Keith
www.woofertester.com (http://www.woofertester.com)

[Zilch]

Well, I'm not Giskard, but I do kinda understand your response. :p

Thank you, Keith....

[We DO play the same tunes, sometimes, tho....]

[WTPRO]

Sorry 'bout that Zilch

Doa! Is this me?-> :homer:

(If the emoticon fails to show, thankfully Im not yet quite like Homer Simpson)

Thats what happens when I am flipping screens and not using the 'quote' feature. As an FYI, what I was referring to was a special build I did for Giskard where he wanted to create an impedance acurate TS parameter list for mids and tweets. What I came up with was a back annotation for the Vas derived parameters (BL etc...) using efficiency and piston area. From a pure electrical model standpoint this worked pretty darn well if I dont say so myself.

Though this would not be that usefull in the initial Vas calculations (what goes wrong if Sd or No are slightly off?), it *can* be used in successive runs as a fast way of computing a full TS parameter list from only the Q/Fs data. This would for example be usefull as a driver heats up under stiff usage.

If you want to give this new method a try, I can send you a special version like I did for Giskard. The bottom line is that I would like to know if this would be a usefull feature for the next full release.

Back to mids and tweets. Assuming the mid/tweet is a normal 'piston' this should not only work for generating electrical impedance and phase, but quite possibly also produce some usefull acoustic impedance and phase. Maybe you can see where I am going with this with regards to a multiple modeling of a woof, mid and tweet. I suspect however there will be a problem as soon as the driver gets sustantially above Fms, in which case the piston rarely acts like an ideal piston. What happens with a horn is beyond my thinking at the moment... unless I use actual measured in-air phase and magnitudes.

Best regards
Keith

[spkrman57]

Is is necessary to limit the current settings? And if so, to what current limitations should I follow to be safe?

Sorry if this sounds like a stupid question, but I thought I would ask before I might accidentally cause harm to a driver.

Regards, Ron