T/S deviations from factory specs?

[mr_push_pull]

The local Visaton representative told me that with Visaton drivers the deviations from the factory specs of T/S parameters are within +/-5%. I'd like to believe that, since building a box for measuring Vas does not appeal too much to me, but I've heard reports of many good branded speakers with huge deviations. For instance using a different material for the spider yields big changes in Vas.
I believe many of you have measured the T/S parameters, what were the deviations?

PS: I'm aware that it's possible not to be in the most appropriate section, but Google does a poor job at translating from German, and the "General" section seemed the fail-safe option

[walwal]

http://www.thielesmall.com/database.asp#

Here You find some T/S-Parameters.

[mr_push_pull]

This is what that page tells me:

Summary of Woofer for Hifi of any diameter from Visaton, undetermined production: Sorry, no data matches yor selection. Please try with other parameter combinations.

I conclude that this page doesn't know any Visaton Hi-Fi woofer. I tried random combination but I couldn't get one parameter, I keep getting that same message.

[walwal]

There is a whole bunch of Visaton-speakers at this page.

Just go to driver-parameters and type "Visaton" into "branch".

.Loudspeaker drivers of the following brands can be found in our database:
......, Vifa, Visaton, Volt, Westra, Yamaha, Zachry, Zomax,


DO NOT type "undetermined"!!! Type "active"

[UweG]

If you calculate Cms, Mms and Bl out of the T/S parameters and then measure several drivers you will find:
- Mms strongly depends on position of the driver during measurement. If you really fix this, the tolerances between drivers are low.
- Bl should not vary too much at all if the measurement is well reproducing
- Cms depends on the voltage you use and on what you did with the driver in the past. Here the differences are bigger.

For designing of enclosures I believe we all use the Visaton parameters and I've never heard that this has caused problems.

[mr_push_pull]

OK, I managed to get some data, I don't know what was it that I was doing wrong.
But, hold on for a second... I thought the whole idea with that page is that it had measured parameters. But looking at the specs for the W170S driver I see that they are exactly the same with those from the Visaton website, and it's impossible that the measured parameters are 100% equal to the factory ones. What's the catch than? I was looking for real, measured specs, what would've been the point of asking here when I could have gone and get them from the Visaton website?

UweG, I understand what you are saying there, but let me take one example. Some known brand changed the material used for the spider in one of their types of drivers, and that resulted in a Vas that deviated with over 50% from the factory specs. Since Vas has a major influence over the box volume, designing a box for that driver using the factory specs would have made as much sense as picking a random driver and put it in a random box. I asked my question because I wasn't sure if Visaton uses this kind of practices. Hoping that they don't, I'll stick to my box design computed from the factory specs. And I'm comfortable with it, because, really, I'm too lazy to build a box for measuring Vas.