Foam Plugs

Rodman99999, "If the plugs are closed cell foam; the alignment becomes an acoustic suspension."

Maybe, but probably not. What you have is more or less a sealed box alignment. Acoustic Suspension is more specific than that, and requires certain parameters be met. Not that the ingredients involved in implementing bass reflex and Acoustic Suspension designs are mutually exclusive, but in my opinion, it's difficult to have both bases covered. I'm confident you know the differences based on our prior discussions, but just want to make sure there is no confusion on the part of those reading here.

I agree with your statement on the reason the plugs would be supplied. However, I remain dubious as to whether a design that was presumably optimized with a bass reflex alignment would not be facing a one step forward, three steps back situation with the plugs installed.

Then again, given that many who design loudspeakers today are more possessing in cabinetry/veneering ability than the requisite mathematics and engineering involved in loudspeaker design, the assertion I made about "presumably optimized" bass reflex alignment (some would argue there is no such thing) might be asking far more more than said folks are capable of.

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.

Eldartford, ""Sealed box" they may be, but not truly acoustic suspension." Agreed. That was the point of my initial post.

"A true "acoustic suspension" speaker system involves a woofer with a free air resonance of about 15 Hz." Disagree. A woofer designed to be used in an Acoustic Suspension alignment is not dependent on free air resonance, but the other parameters you and Rodman99999 have been discussing, along with a powerful motor structure. For example, it would be difficult to find an 8" or 10" woofer with an Fs of 15 Hz, yet a properly designed driver of this size could serve the intended AS purpose well.

Incidentally, Villchur's first designs used the silky material taken from the outside of mattresses, as he considered it the best thing he could get his hands on to implement his theories. Even though he felt it was crude, things worked out beautifully, and as they say, the rest was history.

Eldartford, your understanding of the subject is a textbook case of "right church, wrong pew".

Eldartford, "no pontification." Do you have something against us Catholics?

Seriously, though, what I mean is that your statement, "A true "acoustic suspension" speaker system involves a woofer with a free air resonance of about 15 Hz" is incorrect. It really is as simple as that.

AS woofers were not always 12". They were often 8" or 10", with an Fs of 25 - 40 Hz. While certainly not high, not the 15 Hz you stated as being a requirement, either. Fs in and of itself was not what made the driver suited to the task - or not. Instead it was some of the other things you mentioned.