Subwoofer Plug

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

JohnnyB

Your are describing the properties of a driver optimized for a AS design. The OP does not have that. He has a ported design he wishes to convert with a plug. I only mentioned that he can get SOME of the benefits of the AS design (not all of them) by plugging his ports. He will also give up some of the low end frequency response he gets with a ported design.

Telling him to buy another speaker entirely is not that helpful IMHO.

There are numerous manufacturers (like B&W for example) that supply port plugs for their vented speakers. No one says this will convert their ported cabinets to an optimized AS design, but it may provide benefits. I myself do this to tighten overall bass response when using my HSU sub (which is also sealed) and adjust the crossover to compensate for the higher CP of the plugged B&Ws.

You can also find numerous speaker design guides that mention the use of the same driver in either AS or ported cabinets. Does not mean that using these mulipurpose drivers in a sealed cabinet is a bad thing. The driver does not have to optimized for AS to be called AS. That's nitpicking.

Dhl93449... For true AS the driver must be quite specialized, and completely useless in a ported enclosure.

Just curious, but have you ever held in your hand a 10inch driver with free air resonance of 13 Hz? Such were in my KLH12 and KLH5 systems. Question 2... can you find such a driver on the market today?