Foam Plugs

A true "acoustic suspension" speaker system involves a woofer with a free air resonance of about 15 Hz. My KLH12s were 14 Hz. You can't find a driver like that today. Evidently speaker system designers today just don't trust that trapped air creates a spring. A spring more nearly linear than any driver's compliance.

"Sealed box" they may be, but not truly acoustic suspension.

Mr T- They laughed at Bob Fulton too, when he'd walk into a shoppe with his 'Gold's'. The laughing stopped, when the music started. Look at the revolution in cables he started. Mr E- There are a few drivers available, with fairly long throw voice coils and wide surrounds. If one were really intent on loosening the compliance more for a true Acoustic Suspension design; they could do what Villchur did, and cut away most of the spider(leaving just enough to keep the VC aligned in the gap).

Rodman99999...Long throw and wide surrounds...yes. But what is the Fs?

It would be nice to know what size woofer you're talking about. The last drivers I shopped for were 10", and that's been a couple years ago. I couldn't buy the drivers that Lyngdorf used in their W210(raw) or anything equivalent, so I stopped shopping and stuck with my Nestorovics. Change the compliance(like by skeletonizing the spider) and/or moving mass, and you'll change the free air resonance(the Cms will change over time also). Lots of variables.

Rodman99999...The KLH driver was 12". I happen to know its Fs because I had to buy a replacement from KLH, and every driver was tested, and the Fs marked (to a tenth Hz) on the cone.

With a "real" AS driver you can bottom out the cone simply by handling it. It is an incomplete device without its enclosure. Perhaps the "loosest" driver I ever had was a Wharfedale 8" with flannel cloth surround. This was before the days of foam.