I am starting to find out how little I know about these things. This is more complicated than I thought.
Take a look at this sub.
Tuning frequency is around 20 Hz. Scroll down to the cone displacement graph and note that at full power 500 watts, woofer cones displacement is only 4.75 mm.
Now look at the vent air velocity and you see as cone displacement decreases vent air velocity increases, up to 18 mm/sec. So it is the vent really moving air.
It would be the same for a PR, the PR displacement would would look like the graph of vent air velocity.
Below Fb cone displacement increases but as you can see form the graphs, sound output rapidly decreases.
It is all about acoustic transformation.
A loudspeaker cone is actually very inefficient at producing sound.
So sealed, IB and open baffle designs are inherently wasteful. That is why expensive drivers with large excursions and huge amps are required.
The most efficient transformater is the horn. Unless very carefully designed colorations intrude.
The ported and PR designs are fairly good acoustic transformers, but reproduction is inherently resonant. While this can be minimized with careful design, I never get that feeling of the sound not being reproduced.
Pipes give the option of still having transformation (i.e. port output) and still allow for critical damping, so that if done properly you get that real sense that the bass is in no way artificial or reproduced. Admittedly efficiency is sacrificed compared to an undamped fully resonant pipe, but the trade off is still attractive.
I'm very sensitive to a resonant bass, and it really destroys the illusion for me. So I find the real estate you have to devote to TLs or horns worthwhile.
