Great explanation, David, and it wrapped up neatly my own thoughts and experiences of building bass boxes years ago for car subs. Getting an enclosure to be smooth across the lower end, and to still be "musical" was always the challenge because the interior of any vehicle doesn't allow enough room REALLY LOW freqs to happen. Bass boxes were nothing but the "one-note wonders." Today, as we drive down a street and pass/being passed by a vehicle with a box, all that is hear is BOOM with no real musical quality. SMH
The closest thing that ever came to getting some decent low to mid-bass were labyrinth-designed enclosures.
I realize I am hijacking this thread, but it brought back a lot of memories.