ultra compact subwoofers...?

Neither one of them is ported. More than likely a lot of eq to get down low enough/loud enough in such an enclosure. These are really meant for people that do not want a huge amount of output and are really just looking at augmenting bass duties from small door speakers.

Exactly! In fact, they are usually designed to fit behind the seat of a pickup. I used to have a small wedge, slightly thicker and less modern, that worked really well in my small pickup. Here, really well means that there was a lot more bass than what I could get out of the little 4" dash speakers.