I tried it a long time ago, and it really did not work that well in a car. The two main issues were: 1) the trunk of a hatchback is really is not sealed well enough, and 2) the drivers really do need the benefit of a tuned enclosure.

For my credentials, I used to be a high-end car audio installer. And, I had studied audio engineering as a specialty within my Electrical Engineering degree. Back in the day, I had designed and built tuned subwoofer enclosures having access to the best knowledge, equipment, and training.

First, I found that I could never seal the hatch area well enough. So, too much air leaked around the baffle, and that canceled-out a significant portion of the output. You can correct this with more power and more drivers, which helps to some degree.

Second, there was no tuned enclosure to help control the speaker's resonant frequency. So, the sub system tended to sound boomy and non-linear.

Third, there was no tuning to help the driver extend below its natural low-end roll-off frequency, so the subs tended to lose their impact and sound muddy on the low end frequencies.

When you add power to compensate for #1 and #3 above, the non-linearity of #2 really comes to haunt the system. It just sounded like a big, loud mess.

I did achieve the goal of creating more room in the trunk. But it came with significant audio sacrifice.

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