Foam Plugs


I noticed that some ported speakers come with foam plugs.

In what situation would you use these? What results can be expected from using these?
agiaccio
Mr T- Yes, I do understand your point. However, most make no distinctions between sealed box and 2nd order/acoustic suspension designs nowdays. ie: This site moves directly from a 2nd order alignment(calling it variously, "2nd Order", "Acoustic Suspension" and "Sealed Enclosure"), to a 4th order alignment: (http://www.danmarx.org/audioinnovation/theories.html) I do agree that IF the woofer and enclosure were optimized as a 4th order alignment, it would not be optimized as a 2nd order, with the vent sealed. BUT- the woofer would still be operating with the enclosure volume acting as an air spring(acoustic suspension). Actually- Villchur came up with the "Acoustic Suspension" design around 1954, and started building speakers with Henry Kloss, somewhat before A. N. Thiele published anything concerning speaker parameters, or cabinet alignments(around 1961), so things could actually get (somewhat)"optimized."
Rodman99999, "However, most make no distinctions between sealed box and 2nd order/acoustic suspension designs nowdays." That solidifies my feeling regarding the dumbing down of the craft over the past decade-plus.

Beyond that, thank you for your explanation.

Sadly, it seems as if cabinetry occupies the lion's share of loudspeaker design today. If one ever saw his own personal loudspeakers, they would guess that Bud Fried must be turning over in his grave right now.

I take a more skeptical view of how successful a woofer designed to be used in a vented alignment would do in Acoustic Suspension duties as their responsibilities are far more different than the average Joe understands. Claw and upholstery hammers both drive nails, yet clearly serve very different functions, as do Acoustic Suspension woofers and those to be used in bass reflex cabinets. People trivialize this these days, due to a lack of understanding and familiarity. The (low - mid power) tube renaissance brought along with it the need for maximum loudspeaker efficiency, which usually means bass reflex speakers. Now, the pendulum has swung too far the other way, and folks are missing out on the advantages Acoustic Suspsension brings to the table.

Anecdotally, a friend of mine, whose loudspeaker ports (made of cork) deteriorated to a great degree over the years, and then replaced them, experimented with stuffing them. He was not at all happy with the results, and soon removed the material, never to go back. That put a real bad taste in his mouth about sealed speakers in general. To me, it was not surprising, as the Focal made woofers in his speakers were simply not designed to be used in that application.

Finally, the Acoustic Suspsension alignment is probably the greatest post war advance in high-end audio. Most agree it was the very thing that brought (en masse) stereo sound reproduction into the home. Think about it, would we all be still listening in mono otherwise? Like most implementations of genius, it was amazingly simple. As you know, Villchur had no desire to manufacture a loudspeaker, he simply wanted to sell the idea to a company in the business, and make a few bucks in the process. To put it politely but literally, he was laughed out of every room he presented his idea. I admire the spirit and determination of a man who answers this type of rejection with building one of the most successful high-end audio companies ever ala implementing his vision.
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).