Measured T/S parameters for Visaton W200S‑8 – they are way off the datasheet, why?

[spyros-]

Hi everyone,

I’m a beginner and I’ve just tried to measure the T/S parameters of my Visaton W200S‑8 (8 Ω).
I followed the method described on A4E Audio’s page “DIY Impedance Jigs and Measuring Impedance in REW”.
Here is what I did:

Audio interface: MOTU M2, using the headphone output.

Impedance jig: Impedance Jig 2 with a 100 Ω sense resistor.

Measurement method: Added Mass, first with 20 g and then with 35 g.

The woofer was hanging free in air, not mounted in any box.

Room temperature was 20 °C.

The woofer is new but has already played about 2 hours of relaxed music at moderate level to loosen up a bit.

My results:

ini
fs = 41.5 Hz
Qts = 0.579
Vas = 35.54 L
The official datasheet says:

ini
fs = 30 Hz
Qts = 0.33
Vas = 50 L
That’s a big difference!

My questions:

Is it normal to see such big differences on this woofer?

Is it because it’s still new and not fully broken in?

Or did I do something wrong in the measurement process?

I would really appreciate any advice or experiences from others who have measured this driver.
Thanks a lot in advance!

 

[sm52]

You must meet all the measurement conditions that the manufacturer had in order to get the same results. You won"t even be able to know about it. But it is possible to get similar results. For example, if the manufacturer has Qts 0.33, you can get 0.39, or 0.42. Try changing the sensitive resistor to about 40 ohms. Let the total added mass be about 23 g, let half of the added mass be about 11.5 g.

 

[Igor Kurilovich]

I had a similar problem, but my friend advised me to load the speaker with a signal of about 10 Hz for a couple of hours. I used a ton burst generator, and loaded my speaker in such a way that the cone travel significantly exceeded the nominal. It looked a little scary. But after two hours of such execution, the measured parameters became much closer to those published on the manufacturer's website.

 

[spyros-]

You must meet all the measurement conditions that the manufacturer had in order to get the same results. You won"t even be able to know about it. But it is possible to get similar results. For example, if the manufacturer has Qts 0.33, you can get 0.39, or 0.42. Try changing the sensitive resistor to about 40 ohms. Let the total added mass be about 23 g, let half of the added mass be about 11.5 g.

Thank you very much for your detailed advice!
I will follow your suggestions: I will try using a 40 Ω sense resistor and use a total added mass of about 23 g (with one measurement at about 11.5 g).
I really appreciate your help, I will redo the measurements accordingly and I will keep you updated with the results.

 

[spyros-]

I had a similar problem, but my friend advised me to load the speaker with a signal of about 10 Hz for a couple of hours. I used a ton burst generator, and loaded my speaker in such a way that the cone travel significantly exceeded the nominal. It looked a little scary. But after two hours of such execution, the measured parameters became much closer to those published on the manufacturer's website.

Thank you very much for sharing your experience!
That’s really interesting. I haven’t tried a break‑in like that before, but I will definitely consider loading the speaker with a low‑frequency signal as you described, to see if the parameters move closer to the manufacturer’s specs.
I appreciate your advice and I’ll give it a try carefully. I’ll let you know how it goes!