Subwoofer Plug

Aewhistory... If you google "acoustic suspension" you will find good info.

The acoustic suspension concept is to replace the mechanical springiness of a cone speaker with the springiness of air trapped in a closed enclosure. It requires a speaker with cone free air resonance on the order of 12 to 14 Hz. (Hold one in your hand and it flops around like a dead fish). Such a driver cannot be used with other types of enclosure. Few if any drivers are made today with suitable characteristics. Low distortion is the primary benefit, but a significant secondary benefit is that the appropriate enclosure size is relatively small.

I obtained some makeshift plugs for the ports on my B&W 803's at Wallymart, kids section. Those closed cell foam play balls work great. Just measure your port diameter and look for foam balls that are a bit larger. If you get a reasonably tight fit, they will seal air tight and that is what matters.

And I would not use a foam tube as you can make annoying wooshing port noise from the smaller diameter opening.

An air suspension design just means the driver is mounted in a sealed cabinet, ie, no ports. While the optimized cabinet design for an air suspension (dimensions, volume, etc) will be different than a ported design, plugging the ports on a ported design will get you some of the benefits of the AS design at the expense of low frequency response.

Sorry Dhl93449, Eldartford had it right:

An air suspension design requires a sealed enclosure, but not all sealed enclosure speaker designs are air suspension designs. The bass drivers made today usually come with the specs to determine the enclosure volume and port length and diameter for a ported speaker and the enclosure size for a sealed design. The sealed design is *not* an acoustic suspension design because the woofer's ability to make excursions and return to neutral is entirely dependent on the cone stiffness and magnet strength. In a true acoustic suspension speaker, the speaker cone and magnet strength are significantly reduced along with the enclosure size. The sealed air in the enclosure then supplements the magnet and suspension to control cone motion.

In a standard sealed enclosure, which is much larger relative to the woofer diameter, the sealed air does not significantly contribute to the cone excursion and restoration.

For example, a standard 10" woofer today might require a 4.8 cu. ft. enclosure if sealed. However, the true acoustic suspension designs of the '60s (e.g., AR3a, KLH, Advent, etc.) were mounted in a 2.3 cu. ft. enclosure and produced true low-distortion bass down to around 30-33 Hz. The floppy suspension and thin cone lowered the free air resonance of the woofer to make this possible.

I am old enough to remember when AR came out with their first speaker, which was the AR1...just a woofer. Then they added a high end driver, and the AR2 was born. It blew away every other speaker on the market.

Maybe it is time for acoustic suspension to be reborn. Most present-day audiophiles have never heard true AS, and their reaction might be similar to what happened back in the day.

To Johnyb53 and Eldarford, I have Harbeth and Spendor LS3/5 type two way monitors with sealed woofers. The bass reminds me of the older AS speakers from years ago. Are these considered AS?
Thanks
Yogiboy