Foam Plugs

If the plugs are closed cell foam; the alignment becomes an acoustic suspension. If the foam is somewhat open; it will serve to partially damp the port's output.If your speaker's placement was say, closer to the corners of the room; they could serve to reduce any boominess that resulted.

ProAC provides plugs with some of their speakers, for the reason rodman99999 mentioned. Try is the best way to hear the difference.

Basically, if you got to put your speakers near the wall or corners, then you'll probably need the "foam plug" to help tame the bass "boominess". Of course, there is a part of me that ask the question "why don't they make acoustic supension speakers anymore?". Seems to me, that you didn't have near the issues with speakers placement, back when "acoustic suspension" speakers were the norm.

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.

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."