Sounds terrible, I guess the enclosure is too small, it's properly sealed but my guess is would I have to port it on the rear side of the pillar. Has anyone have seen the RUMION one how does it looks from behind.

 

Looks great but that enclosure is way too small. There are subs made for small enclosures, maybe look into them. Try to calculate the air space available in the cubby hole and look up the specs.

I never taken off the C-pillars, how much extra room is behind them? You could always cut and expand it.

 

First, how is it sealed to the panel, especially the sides? Second, yeah those cubbies are way too small on air space for most 8" subs, even the ones made for small enclosures. Another problem you're going to have is that it is all mounted to plastic which will vibrate massively with any bass notes as it's not designed for it. The stock sub is very low power and I believe has it's own enclosure. if you want to do an enclosure up there properly you'll need to build an enclosure that mounts to the actual side panel and the pillar just goes over as a trim piece.

 

Agree, the plastic and space is the issue. Thanks

 

I would cut the back of the plastic out. Make the box bigger behind the panel. Just my thoughts.

 

The C-pillar space is about 200cu inches without the driver taking up space, not nearly enough. It'll be better to underseat mount them using low volume 8's. I have thought of putting a 5" coax as rear fill in there. Still an ongoing project.

If you cut out the panel to gain more enclosure volume, you'll have a large unbraced panel that will rattle.