Qwiz

I will measure a 20Hz-200Hz sweep in REW.

The vehicle is a Kia Rio UB III 2016, European Edition, 3 Doors. Worth mentioning, once door panels&co. are taken out, that the inside-design looks very strange, such that there is like a tunnel space on both left and right sides, when looking from the trunk, between the trunk and the space where the back-door "is", you could put your hand from the trunk and come to the side all the way to where the back door is. - would not be a box issue, the same subwoofer in the same box sounds good in another car/in another enclosed space - a Home-Subwoofer instead, by keeping it connected to its home amplifier sounds similar - inverting the phase + time alignment + position settings + etc: slight differences, but with the same overwhelming feeling If when changing the listening position (like when I lay flat), the bass evens out and seems normal, wouldn't that suggest an acoustic issue?

Interior Length: ~2,5m Interior Height: ~1,2m Interior Depth: ~1,7m Scenario1: Listening position: Driver/Passenger seat, sitting normal; Subwoofer alone playing: 15-27Hz: good 28-55Hz: undefined/muddy/muffled/doubled/overwhelming 55-80Hz: dipped/canceled/almost non-existent Scenario2: Listening position: Driver/Passenger seat, laying flat; Subwoofer alone playing: 15-80Hz: good Tried without any success: -changing subwoofer position -soundproofing everything but the ceiling Conclusions: -it's not a crossover issue -it's an acoustic issue How would you approach this issue?