Need help with tuning my box...

[BenzBass]

I decided I was going to build my own box because it's summer and I'm bored, and I was tired of my tiny 2 cubic foot box for my 15" Kicker CVX. So I went to Lowes, got my materials and started building. The box itself I made it to its maximum size that I could fit in my trunk with relative ease. It's 36" wide, 16" high and 12" deep. I wasn't able to go any deeper or I wouldn't have been able to fit the box in my trunk because of the stupid trunk design in the 1996 Mercedes C220. The box is ported and the port is 3.75" wide and 14.75" high. I hope it's okay to post a picture in here because heres a picture of the design:

So in short, what I'm getting at is that it is tuned too high and doesn't do too incredibly well with the lower notes which disappoints me. So, is there anything I can do to tune it lower without having to start all over? Hope I can get some help on this, and I only really got into car audio back in October when I got my first car, so I know very little about all of this compared to most everyone else on here. So with that being said, excuse noobish mistakes and this was my first box I ever built.

[BenzBass]

anyone able to help? hope its okay to bump a post a day after

[Crandis16]

if possible, you should try to do an L-shaped port as opposed to a labrynth style port, unless you have strict dimension limitations.

are you using MDF or particle board?

I think you should tune to lower 30's for 15's.... anyone please correct me if I'm wrong

[Joe X]

You have 3 cubes gross internal, the CompVX 15 needs 5 cubes net.. so you don't have the space for ported but you could make it sealed, 3 cubes would be enough nice.