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.

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

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.

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.

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

Trelja...I concede that the Fs of 14 or 15 is what I would expect for a 12" or 15" AS driver. 10" or 8" would be higher, which is perhaps why such drivers are less successful as AS drivers.

Note that my point is not that you can't achieve a rational sealed box alignment with a tight driver, but rather that the linear quality of the cone spring is degraded, affecting distortion, about which T/S has little to say.

My affection for acoustic suspension goes back to the AR1. This was a woofer-only box. The better-known AR2 was created by adding a tweeter.

Pontification is not unique to Catholics. In fact it refers to people who are not the holy father talking as if they were.