the Kia EV6 trunk-mounted "Meridian" subwoofer is wired backwards, from the factory. But it's a simple 5 minute fix rearranging four wires that power the subwoofer.

locate the Meridian subwoofer underneath the EV’s false floor out back, remove an orange clip, and swap the corresponding pairs of wires so it shows black-red-black-red from top to bottom rather than the red-black-red-black pattern you’ll find in unmodified examples.

https://www.thedrive.com/news/kia-ev6-owners-are-rewiring-their-subwoofers-because-the-factory-set-them-up-wrong