hi guy i'm looking for a little help here i have a 94 eclipse running one nightshade 15 d1 and a saz 1500d i am trying to get this thing louder as i know it can with my current set up it does a 143.8 at the head rest and a 121 drive by the box that i have now is sub up port up at 4 cuft tuned at 40hz here is the demention for the box 24h 31w 15d it pretty much the max i can get in the hatch area as it hits the back glass if any one would be willing to help with an design it would be great as i can build them just not so good with the design and tuning part

From what i've gathered just from hearing others running nightshades, try the following-

Sub up, port back, approx 3-6" away from hatch door and make the box 3 cubes net instead of 4.

ttt

Are you running your SAZ-1500D at .5 ohm or 2 ohm?

.5 OHM

If your running at .5 ohm make sure you have the eletrical to back it!

Are you looking strictly for (SPL) numbers?

Try a smaller box as shizzzon recommended and play with tuning and placement in your vehicle.

Find your resonant frequency of your vehicle and tune somewhere around that frequency.

Sound dampening will also help.

I HAVE THE ELETRICAL TO BACK IT UP 200 AMMP ALT WITH A RED TOP AND TWO 1010CCA POWER VOLT BATTS 3 RUNS OF 1/0 GA WIRE FRONT TO BACK I'M JUST NOT GOOD WITH THE DESIGNING AND TUNE OF A BOX I NO I NEED SMALLER BUT AS FAR AS WHICH WAY THE SUB NEEDS TO POINT AND WHERE THE PORT NEED TO GO

with what you have, you seem to be at least a little serious about audio..imo you should find your res freq first, then build a couple boxes with diff configurations to find out what works best for max spl. as far as boxes go...i have my 15 in 3 cubes tuned to 33 w/ 56sq in of port. tuned for daily my res freq. still has me peaking with 148s at 48hz

Why not get someone to build you a box then? It would be a good investment IMO if you're having troubles doing it yourself

or buy a design from fisher customs or pound that sound and build it yourself