Impedance sweep?

[Rick Auricchio]

I've seen mention of running an impedance sweep to find air leaks.

I believe I understand the concept: You measure driver impedance over its frequency range to spot unexpected peaks. The normal cab tuning should cause a peak; something else indicates odd tuning, from a leak.

Tools needed: Signal generator, impedance meter.

So what's an economical impedance meter, a method using one or more multimeters, or a combo device that runs the sweep?

[Sydney]

Tools needed: Signal generator, impedance meter.
So what's an economical impedance meter, or a combo device that runs the sweep?

Define economical...A Woofer Tester II ( $159.95 )
http://www.woofertester.com/wt2product.htm
It generates an impedance sweep and T/S parms in a few minutes ( including calibration )

* Some impedance meters only offer a single frequency test - Not a sweep of all frequencies

The old school method ( which involves manual recording/plotting ) requires:
A sine wave generator ( w frequency counter )
An AC volt meter
An accurate resistor ( for calibration )
And optional but ideally - an oscilloscope

[Rick Auricchio]

$159 isn't bad, but unless I'm building a lot of cabs it's a bit on the high side.

[Sydney]

Valid point
For me - building cabs for a long time now, and planing on building many more in the future - It was a investment.
If you have to buy the individual items ( I listed ), for quality/accurate generators/counters/ and meters you can easily exceed the cost of a WTII.
Also manually recording and charting detail and doing T/S measurements is a boring & tedious and takes a lot longer than a few minutes.
Of course, there are test jigs and software that utilize a sound card as a measurement device - BUT I tried several and found the software clumsy and I wasted a lot of time just trying to get it to work.
That's not to say you can't build a jig and download software and get it to work.
You will have to invest some time in set up.
You can be up & running w WTII immediately - software is continuously being updated with additional functions being added, and upgrades are free ( so far ).
WTII generates an impedance curve w the electric phase over-laded.
It's about a user's friendly as possible.

[kdchandler]

Last year (I think) there was a discussion about the Woofer Tester and someone mentioned a similar product from which the WT was derived. The other unit was described as more capable, but I can't find it with the search. Does anyone remember the other box?

Thanks

[Rick Auricchio]

Though I have a PC I rarely use, I'd prefer a Macintosh program. A little searching turned up:

http://supermegaultragroovy.com/products/FuzzMeasure/

which might do the trick for US$150. I've got the audio interface for my MacBook Pro, and I've downloaded the demo version.

[Bill Fitzmaurice]

Last year (I think) there was a discussion about the Woofer Tester and someone mentioned a similar product from which the WT was derived. The other unit was described as more capable, but I can't find it with the search. Does anyone remember the other box?

Thanks

http://www.partsexpress.com/pe/showdetl ... er=390-804

[kdchandler]

http://www.partsexpress.com/pe/showdetl ... er=390-804

That was too easy. The one I imagine remembering was a different company of which I'd never heard, but it looked similar. Does the WT3 work well?

[Sydney]

That was too easy. The one I imagine remembering was a different company of which I'd never heard, but it looked similar. Does the WT3 work well?

From my understanding:
Smith & Larson Audio was the original source of the WT ( which at one time PE sold - I got mine there).
They had a parting of the ways, & PE went on to sell WTIII.
S & L sells WTII and other products.
They offer free software upgrades for original purchasers of WTII and the TENMA version.
You can calculate T/S parameters, other resonate circuits, test basic parts,
It also has these modules: Box Alignment, advanced Thiele-Small Simulator & Box Analyzer
also a speaker burn-in function.


WTIII is Supposed to be a stripped down version of WTII. Go figure.

* Also TENMA (MCM) sells a version of WTII.
Smith & Larson also support this

[kdchandler]

Thank you. This was it!

I spent some time reading the WT3 reviews. The simple reviews are mostly thumbs up. The detailed reviews are more varied. They do have a special that includes a digital scale with the WT3 for $99.88 and free shipping. This is a good deal it it works well.

Has anyone used both it and the older units?

[remix]

Has anyone used both it and the older units?

I've had 2 of the old WT2 from PE, both are now dead, went up in smoke.
Think i'm going for the original WT2 this time.

Dag

[Sydney]

I've had 2 of the old WT2 from PE, both are now dead, went up in smoke.

Do you know what caused it or what your were doing at the time?

Mine is also a Harris Tech ( purchased from PE ).
After it went out of warranty - I had left the "box" ( it is a modified USB external sound card ) after a sweep and it was generating a low frequency tone on a woofer.
I had forgotten about it ( for hours ), until I smelled the tell tale odor of hot circuits.
Based upon the impedance/phase load ( low and negative ) of that woofer at the held frequency - I think I was putting a worse case load on the 5V USB line with a lot of current draw.
So now I am careful not to hold any generator at these low impedance/ negative phase valleys for extended periods.
Since then, no problems w latest software upgrades from S&L.

[remix]

Mine is also a Harris Tech ( purchased from PE ).
After it went out of warranty - I had left the "box" ( it is a modified USB external sound card ) after a sweep and it was generating a low frequency tone on a woofer.

I did the same with the last one i had, i think that was the problem.
The first time i blew it, it was my mistake, i pushed the cone in and out with the wires connected.
I think that generated current that the box could not cope with.
Thinking about it afterwards its a dumb idea, but it is not statede i the user manual not to do this.
Dag

[marty]

i got one of the wt3 things last week, and so far i think it is a piece of crap.
maybe i dont know how to use it properly yet, or interpreting the graphs it makes.
was trying it out on deltalite 2512 and piezos of various kinds

[bgavin]

I've read far too many failure stories about this CCS, so I decided to keep looking for a better solution. I'd like to find something that will integrate well with the TrueRTA sweep.

Perhaps I don't understand the nature of impedance sweeping yet, but if TRTA can accurately read microphone voltages in a quick sweep, there is no reason it cannot do the same for voltages used to measure impedance.