Subwoofer setting

A car interior can boost bass as much as 20db or more. But it is not always the deepest bass.

Halcro, you sort of answered your own question with the term "stomach churning" which indeed it is: ie. a mechanical vibration -- like SenSurround -- but not an acoustical vibration. And if anyone rolls down a window, the "room" becomes the "whole outdoors"!

"How do you explain the stomach-churning bass able to be produced in some car installations?"

Don't confuse "pressure" with well-articulated sound at defined frequencies.

If you use a test disk with separate signals at various frequencies and a sound meter you can see for yourself if your car sub is producing "sound" at very low frequencies or just pressurizing the passenger compartment.

Now what you hear outside the car is a very different thing, because the "room" has no or very distant boundaries.