Measuring TSP: Easier Than I Thought

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Well, since there is no "General Speaker" forum here, I figured I would post this here since I know many of you who hang around here, and since FR rules! :yes:

I have resisted trying to set up a Thiele/Small Parameter testing system because I had assumed it was far too complicated/difficult to do.

Recently, however, I stumbled onto a post in another forum where a guy was talking about how easy it is to do with Ulrich Müller's "audioTester 3.0".

I downloaded the pdf user guide first, read through the section on measuring TSP and thought "I can do that."

That evening I dug through my random parts and found a 10 ohm resistor, a 3.5mm male to 3.5mm male headphone cable and a couple of spade connectors. Before long, I had my "circuit" soldered together (more of a custom cable, really) and it all checked out with the ohm meter according to the diagram in Ulrich's PDF.

Once the "cable" was done, it was literally a matter of plugging one headphone jack into the line-level out of my sound card, the other headphone jack into the line-level in of my sound card and the speaker spade connectors to the driver terminals. (I coloured the jack destined for line-in with a blue sharpie and the other end was already green, to match line-out).

Once hooked up, you just run the program, set your input and output devices, sample-rates, etc. and then follow the directions in the PDF. For initial testing of the cable and application to see if it worked, I just used a "loonie" and some tape for the second run. Today, I picked up some Play-Doh and a new battery for my digital scale, then weighed out 20g of the Play-Doh. This worked better.

Anyway, for anyone who wishes they could measure TSP but who finds it intimidating; just jump right in. It is easy.

If anyone would like, I can take a photo of the cable I made and post it here.
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It basically takes the left channel out and feeds it back to both the right and left channel input, but it diverts one channel through the 10 ohm resistor and the driver while the other channel is wired direct. The direct feedback channel is the reference channel which the driver channel is compared to.

(As far as I can guess, anyway :) )
Just an FYI. Added mass is not as accurate as known volume. It works. But not as well. Vas is the hardest to get right.

Thank you. I got that impression by the variability in the Vas measurements. Some day I may build a testing enclosure. The thing is, Ulrich recommends different known volumes for different sized drivers. That sounds like a PITA to me. :yes:

For now, I will simply do repeated tests, perhaps with different masses and then average them. Should be good enough to get a better tuned enclosure for my "sub" than I have now. :D
Thanks for starting this thread. I have always wanted to do this but could not justify spending $100 for the Dayton Woofer Tester. So all it uses is a resistor and some cross wiring, rest is software?
Very cool. Does it work in Windows?

Yep. Wire, resistor, sofware runs on Windows. Easy peasy.

Glad that I kept one computer in the house with a Windows XP partition I can boot into. Didn't try it in WINE or VMn but I suspect it would be wonky.

By the way, the software is "free" but with a time limit. The time limit is only annoying while you are dicking around with the setup and figuring it out. Once you become efficient at it, you can easily get a few measurements done before the program quits.

But heck, I'm just going to buy it. It is cheap!
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