2002 Nissan Maxima Subwoofer Box

Time to add some bass. My requirements started pretty simple. Build a box for my JL 12w6 sub to fit in the back of the Maxima allowing enough room for golf clubs or groceries. I then looked at the trunk and knew it was going to be a bit more difficult than that. I had hoped for a simple square box, but due to the angles in the trunk, that was not going to happen. To make matters a bit more difficult, I wanted the sub facing the cabin instead of the back, so there went the perfect location for my amps and processors. After some measurements, I started drawing out a complex design which included a location to mount two 1 farad capacitors and my amp. Lots of calculations later and I came up with an enclosure that allowed appx 1.25cf of airspace. The enclosure itself is actually two enclosures mounted together. A front "angled" enclosure and a rear square enclosure with a common "center" board. A large opening is cut into the "center" board to allow the front and back enclosures to become one. If building this style enclosure, be sure to add airspace to your calculations for the section of the "center" board you remove.

Tools/supplies Needed:

At a minimum: jig saw, tape measurer, pencil, phillips screw driver, wood glue, silicone, fiberglass resin, one or two paint brushes, cheap bucket, spray glue, razor blades, box carpet, wood and 2" screws. To make things much easier: Table saw, router, circular saw, brad nailer (helps to nail the boards together before screwing), drill bits, sander, clamps, T-square, long metal ruler, etc...etc...

The Design:

The above design fits the contours of the trunk pretty well. I did not even have to remove the factory sub for clearance and it allows for mounting locations of the caps and amp. The Xover was an afterthought/need but I had plenty of room on the side for mounting

Board Cuts:

The box was created utilizing .75" MDF (Medium Density Fiberboard). I mapped out the board cuts and cut them all at the same time. When mapping out the cuts, always allow for the saw cuts. It can get annoying when you align two pieces together and one is off by 1/16th or so...

Step 1 - Back of enclosure:

I started the enclosure by creating the back of the enclosure. I build the outside frame, then positioned the brace. The brace will be the seperator from the sub enclosure to the area holding the caps. Boards were glued and screwed into place. I then laid the frame on the wood used for the back of the enclosure and drew a template for the hole over the cap section. I cut the section out, then glued/screwed the back onto the frame using 2" course drywall screws. All screw locations were pre-drilled to ensure a proper fit.

Step 2 - Front of enclosure:

Next was to create the front section of the enclosure. I started this section by building the frame for the front. These four pieces were glued and screwed together. I then positioned the frame on the "center" board of the enclosure and marked its inside location with a pencil. I moved the "center" board to the back section and marked the appropriate location of the brace (you can see the marks in the first picture to the left). Since the front of the enclosure was going to be mounted to 1" runners, I drew out the appropriate section to allow for them, then cut the section out with a jig saw. I then cut appropriate lengths of 1"x1" stock and mounted them to the "center" board in proper location for the front to mount. The "center" board was then glued and screwed to the back section of the enclosure. The front section was then attached by screwing into the 1" runners. See the 2nd picture showing the front section attached along with the 1" runners mounted.

Step 3 - Sealing the Enclosure:

Being a sealed enclosure, nothing can be worse than air leaks. Instead of using silicone around all the edges, I prefer to completely coat the inside of the enclosure with fiberglass resin which can be found in any automotive section or most home improvement stores. I grabbed a can and a couple of very cheap disposable paint brushes. In a cheap plastic container, I mixed the whole contents of the can with the whole bottle of hardner supplied within the kit. I mixed the contents well, then proceeded to pour the resin into and around the enclosure. I then worked the contents around with the brush and by tilting the box around. Once the resin started to harden, I left the box overnight until dry.

Step 4 - Front section + Sub:

Time to finish the enclosure. Take the final board and draw two lines from corner to corner in order to find the middle. Put the sub on the board face-down and etch the outside. Follow that by drawing a smaller circle in the one you just drew. This inner circle should allow enough space between it and the outer circle for the lip of the sub. Cut this inner circle out. Since I needed to seal this board to the enclosure, I used silicone on the frame, then mounted the board with screws. The enclosure is now done and ready for test-fitting.

Step 5 - Amp Rack:

The amp rack section of the enclosure was an afterthought. To create this section, I measured the available width on the back of the enclosure and cut a frame to fit that was appx 2.5" high. I utilized 1"x1" runners similar to Step 2 to mount this section. If you are wanting to use plexi-glass and fans, this section will need to be higher. I wanted the amps heat-fins to show, so I took this opportunity to measure up and cut a 1/4" sheet of plywood to the size of the amp section. I then determined where I wanted the amp, and marked this location on the 1/4" plywood. This section was cut out and set aside to be carpeted.

Step 6 - Carpet the enclosure:

For this step, you will need some good spray glue (I prefer 3M brand), sharp razor blades, and some box carpeting. There are two kinds of box carpeting, one with backing and one without. I prefer to utilize the carpeting that does not have a backing as it is much easier to stretch and work with. Of course, that's not what I was able to get, so I had to work with the stiffer material. I would suggest doing this in a well ventilated area and use liberal amounts of glue. You will find it is easier to spray the glue and let it set for a few minutes if using the carpeting with backing as the time allows the glue to get tacky. Take your time on this section. Try and not wrap it like a Xmas gift. I also carpeted the 1/4" plywood cover for the amp section at this time.

Step 7 - Mount equipment:

Once the box is carpeted, it is time to mount everything. I started by placing the amp on the amp section. then aligning it properly with the 1/4" plywood cover. The amp was screwed into place. Next came the caps. Mounted the caps and power distribution block. Four holes were drilled into the enclosure for the amps power and grounds which were strategically place. The amp was then connected to the caps bus-bar. Another hole was drilled for the subs speaker wires to poke through and they were connected to the amp. Silicone was utilized to seal the holes for the power, ground, and speaker wires. The sub was connected up and mounted after putting 1lb of polyfill in the box. Finally, a 1.5" hole was drilled in the top of the amp section to allow RCA's and speaker wires to be routed. The enclosure is mounted in the vehilce via two "L" brackest on the front of the enclosure (screwed to floor and "center" section to the left and right of the front section). Pictures are below:

What I would change?

I would definately change a couple of things if I were to do it again. While the enclosure fits OK, it could fit better if the bottom corners of the back section were angled somewhat. This would have allowed the enclosure to move another inch or so towards the back seat. As it is now, it's not really an issue as it does allow more room for the sub to breathe. I would also create a cardboard stensil of the sub to make cutting the sub hole easier. Finally, I would utilize plywood instead of MDF for the front of the enclosure as MDF does not like the sub screws and would hate it if I had to remove the sub.

Disclaimer: The author will not be held responsible nor held liable for any damages due to these instructions. Anyone following these directions are doing so at their own risk. This Documentation may not be distributed without the authors consent.