Trunk Setup | Part 1: The Enclosure

I am super happy with the trunk setup end product! It looks amazing, but surprisingly it sounds even better! In this post, I walk through just the basics of how I, along side my coworkers, achieved a custom trunk enclosure. I wanted something unique. The goal here was to not have "wake up your neighbors" kind of bass, but to be something that everyone could appreciate. Something smooth and rich, yet tight and powerful. Something people could listen to and just want more!

With these things in mind, I chose two JL Audio 8W7's. No other speaker sounds like a W7, it has such a rich, unique, and powerful sound that is delivered with excellence, it's the perfect fit! It checked all the boxes in what I was looking for with this audio system. Originally, I was hesitant using only two 8 inch subwoofers, I thought, "will it be enough"? But now, my favorite thing when people listen to my car is ask them to guess the size. Most commonly, it's, "two 12's"! However, I have even had some people guess "two 15's"! I just laugh and say, "Its only two 8's".

These speakers have such a presence when listening to them but, this brilliant sound does not come easy. The internal volume of the enclosure has to be built to the exact specification. Along with the port volume, frequency, and displacement. There's lot of math that is required to build a ported enclosure to this level. Otherwise the desired sound would not be delivered to its potential. Luckily for me, I had the help of Audio Xtreme and our head fabricator, Justin Iverson to make this enclosure perfect.

Here is a look at how it was done!

PHASE ONE

First, we had to measure how much airspace we had inside the spare tire well. We measured this with rock salt. Yes, the exact same stuff you would use in your water softener at home. We poured the bags of salt into the trunk until we filled the well level to the rest of the trunk floor. Then we poured the salt into our empty box that was built to measure 1 cubic foot of this rock salt. After our calculations, we determined that we had roughly two cubic feet of airspace for our subwoofer enclosure that would be completely hidden when finished!

Next, we are taping off the shell of the empty trunk. Notice how the spare tire well is off center in the vehicle. After taping off the area, we covered the tape in mold release as we are using the car as a mold to build the lower section of the enclosure out of fiberglass!

Now, we are about ready to lay the fiberglass, but it gets messy! We covered everything to protect the paint and our floors from getting covered in resin.

Here is the finished fiberglass piece with MDF wood attached to build the rest of our enclosure off of.

This is the shell removed from the car. Checking for any major imperfections or holes.

Here is an up close picture of how the port is going to work! There is a top and bottom section of the port. The lower part of the port will be inside the box, and the upper part of the port is actually raised above the outside of the box. The two parts of this port will be separated by the "Half pipe shape" part of the box we will go over next! There just was not enough room inside the spare tire well area to fit such a massive port. This was not a problem as we decided it would help us create raised floor that served as a great place to house the amplifiers and keep everything on the same plane.

This is the upper part of the box. The part that we actually wanted visible. We wanted it to appear that this was the only part of the box, and we wanted it to look fairly small. To create this piece, We had to come up with a shape. At first this was a flat, 2 dimensional shape that we then copied onto 29 pieces of wood. Glued them together to make this!

At this time we got to listen to it for the first time to make sure all of our calculations were correct. Not only does the airspace inside the enclosure need to be spot on, the port length, width and height are crucial to tuning to the desired frequency! We were beyond impressed with how this enclosure sounded with these two little 8 inch W7's.

Excitingly, it was game on to make this enclosure look as good as it sounded! This took a lot of work, and two revisions to get it right, but it is far worth it in the end. Pictured above are all the bare panels to trim in the trunk for a finished look. This gave us a multi layered floor to flush our HD amplifiers in, and hide the TwK 88 from JL Audio along with some wiring.

This is the upper part of the box wrapped in a vinyl with a woven pattern in it similar to carbon fiber, which gave me the inspiration for phase 2 of this setup!

Phase one is complete! Finished with the end caps, acrylic light rings around the speakers, and all the trim pieces covered in black carpet to match! Keep in mind we are still working with all the factory trunk liners that we fabric dyed them black to match the aesthetic!

PHASE TWO

Now begins phase 2 of the subwoofer enclosure! At this point in time, I was attending Davis Tech to become certified in Composites. At the end of the class, students are required to do a final project using the knowledge the gained throughout the course. I had the brilliant idea of covering my already finished box in real woven carbon fiber! Pictured is me removing all the old vinyl and glue to prep for the new carbon.

Here is the raw woven carbon fiber material before resin.

This is after the first coat of resin. Took a lot of time to get everything to lay flat without lifting!

This is after the 2nd coat of carbon, and me test fitting the end caps!

Finally, after we countless hours of sanding and polishing, we get to see the carbon in its full glory. It looks so amazing!

I decided I wanted to pull the carpet off the trunk panels and cover them in suede to bring things up to that next level. Notice how I wrapped the two lower trunk pieces as one piece. The goal here was to hide the seam of the two separate trim pieces. If this panel was built as one piece, it would be too wide to fit in the opening of the trunk. In order for it to fit through the opening, it had to be built into two pieces. But I did not want a visible seam in the suede floor. Wrapping this as one piece, essentially allows me to use the material as a hinge to fold the pieces on top of each other, set it in the trunk, and open it up to fit across the whole width of the trunk.

Pictured is the top side of the previously mentioned trim panel. The seam is virtually invisible.

Here is a picture of one of the side pieces!

Next, we built a trunk cover to hide the ugly trunk lid shell. Subaru did not make one, so we made our own. Subaru would not have made one this cool anyway ;)

More on this trunk lid cover to come!

I was super excited to see it mostly put together, so here it is before it went back into the car!

Finally, its all finished! Here is a close up of it all complete.

This is how it sits currently.

Believe it or not, I still have ideas for a phase 3 rebuild!

Special thanks to Jeff and Justin at Audio Xtreme Sound & Security for making this possible!

Another Special thanks to John, Wes, and Matt at Davis Tech!

Thanks to JL Audio for sponsoring this system!