Using DATS V3 for Vas measurements

[GeoWorx DIY]

I have a question on using DATS V3 to do speaker TS parameter tests.
When attempting to determine the Vas: What data is the software asking for in the "Piston Diameter?"
Is that the size of the driver, or the cone, etc?

 

[AllenB]

Normally, that would be the diameter used to calculate Sd. Sd typically includes the cone and half the surround.