View Full Version : Does Vas tell of compliance?

Tom Loizeaux
12-12-2004, 05:20 PM
If I want to judge the compliance, or softness of a speaker's surround, does a low Vas figure tell me it's softer? Doesn't a softer compliance indicate it's ability to work in a smaller, or sealed enclosure, as compared to a higher number Vas rating?
Can someone shed a little light on this?



Earl K
12-12-2004, 05:57 PM
Hi Tom

It would be much better if Giskard explained the relationship between
"Compliance" and the "TS" parameter Qms.

Qms is a unit of measurement that will also describe " Compliance" because its' a measurement of the mechanical resistance .

Vas is a more complex measurement that also involves the weight of the cone
( and air-mass being "pushed" by the cone; Mms ) among other parameters .

I think you've stated your "premise/argument" incorrectly .
A "large" value Vas will just about always indicate a high compliance .

<. Earl K

Tom Loizeaux
12-12-2004, 08:04 PM
This is already helping!


12-12-2004, 09:33 PM
From the Parts Express Tech Talk Page:

"Vas (volume of air having the same compliance as the driver suspension)"

Larger volumes of air would be more compliant.


John Sheerin
12-18-2004, 06:34 PM

p0 = density of air, c = speed of sound, Sd is cone area

So a higher Cms gives a higher Vas, ie, a softer suspension gives a higher Vas.