Space for a 15 under the floor ?? How big is the boot ??16vCento wrote: ↑Fri Apr 02, 2021 12:43 pm The sub itself only appears to be a single 8" but there's easily space for a 12 or 15 as it's under the boot floor.
That 8 of yours would fit nicely in the existing enclosure and looks like it has plenty of excursion though, might bang one in and try it, how many voice oils does it have and what ohm is it?
The Helix subs I have are single 4 ohm voicecoil. If you're using the stock amp you might find it's designed to run an efficient 2 ohm sub and won't have anywhere near enough OOMPH! for an aftermarket sub. There's dozens of alternatives out there though, and modern Class-D amps produce a lot of power from a very compact chassis.