Foam Plugs

Trelja...A low Fs is most definitely an essential element of acoustic suspension. (Not to be achieved by loading the cone with mass). To the extent that the cone compliance is tight (high Fs) its spring restraint is mechanical, not pneumatic. There will always be a mix of the two, but the more is pneumatic the better.

There are two main factors that when combined as in EBP = Fs/Qes.

If you have a low Fs (around 15 to 25) and you have a high Qes (expensive large motor light cone) then you will end up with a low EBP suited for a sealed enclosure (less than 50).

My subwoofer is sealed and uses Fs = 21 and Qes = 0.49 for a EBP of 42. It is a tight sounding (aka musical) subwoofer that sounds quite different from ported designs.

See this

Eldartford, your understanding of the subject is a textbook case of "right church, wrong pew".

Trelja...Kindly explain what you mean. And. please. no pontification.

Eldartford, "no pontification." Do you have something against us Catholics?

Seriously, though, what I mean is that your statement, "A true "acoustic suspension" speaker system involves a woofer with a free air resonance of about 15 Hz" is incorrect. It really is as simple as that.

AS woofers were not always 12". They were often 8" or 10", with an Fs of 25 - 40 Hz. While certainly not high, not the 15 Hz you stated as being a requirement, either. Fs in and of itself was not what made the driver suited to the task - or not. Instead it was some of the other things you mentioned.