Vas of TangBand W6-789S midbass drivers?

I tried measuring them using Speaker Workshop, using the added-mass method. I've tried two different masses (20g and 30g), and I'm getting the Vas to correlate quite tightly with change of mass (5-10% variation between values). I believe this is a small indication that the Vas value is probably more or less correct.

I've measured the diameter by eyeballing middle-of-surround to middle-of-surround, and I've got Sd as 136 sqcm. The datasheet specifies the Sd as 140sqcm. So I'm not too far off.

But my Vas readings are all coming out to 20-22 litres, across multiple mass loadings across two sample drivers. The data sheet specifies 45 litres!

Those of you who have familiarity with this driver, or with the datasheet, or with newbie mistakes with Vas measurement, will you please guide me? What should I trust? In fact, is this the correct datasheet at all? My drivers came in boxes which had "W6-789S" labels on them, but the datasheet does not have the "S". Is the "S" for shielding?

Incidentally, my Fs readings are not that far off... 53-55Hz against the published 45.

Please help. Some of you are total pros at TangBand, so I'm hoping you'll just be able to fill me in from experience. :xeye:
 
[IMGDEAD]http://members.shaw.ca/awooley/pictures/Resize%20of%20W6789Sdatasheet.jpg[/IMGDEAD]
[IMGDEAD]http://members.shaw.ca/awooley/pictures/Resize%20of%20W6789Sdatasheet2.jpg[/IMGDEAD]

Ok the W6-789S is a shielded driver and yes all TB numbers the S after the digits 99% of the time means shielded.
As for the W6-789S
I had the first batch made and these are the data sheets for them that were shipped with the drivers when they arrived.
TB does supply 2 data sheets along with a sample data sheet normally of 12 tested drivers.I have that as well if you send me a email I can send all the files large to you.

Hope this helps out.
 
RAW said:
As for the W6-789S
I had the first batch made and these are the data sheets for them that were shipped with the drivers when they arrived.
TB does supply 2 data sheets along with a sample data sheet normally of 12 tested drivers. I have that as well if you send me a email I can send all the files large to you.
Thanks a lot. :)

You can write to cptarun at yahoo dot co dot in. Alternately, send me email through the diyaudio messaging facility to my mail address, and I'll reply.

In the data sheet you've scanned and posted, the VAS is 29 litres, which is much lower than the 45 litres on their Website. I am getting a (consistent) figure lower than even this one.

Thanks again.
 
Hey raw, have you done a sweep of those drivers yourself? I've found TB's datasheets are not always that accurate/precise. Parts Express usually does their own tests and put a .PDF but they don't have one for this speaker yet.

I wish I could just buy a couple of every driver I see that looks interesting and test it myself, but that would waste far more $$$ than I can afford right now.