When it comes to installing a top of the line car audio system, most audiophiles prefer to build their components from scratch. Of course; not all parts of your sound system can be constructed from the comfort of your home. However, there are certain parts that you can DIY.

One of the most popular choices for car owners is a subwoofer enclosure. While attention to detail is a must, you don’t have to be a master carpenter to put together a sub box. Designing and building your own subwoofer enclosure can be rewarding. Not only does it save you money, but a custom sub box is an excellent way to get the exact look, fit and performance you want in your car.

Depending on how you want to design it, a decent sub box should take you a day or two to finish but only a couple of hours to construct. 

Step One

Before you begin slapping materials together, make sure you have a certain tools on hand.

  • Screws
  • Carpenter’s glue
  • Tape Measure
  • Liquid Nails
  • Medium Density Fiberboard
  • Speaker terminal cup
  • Jigsaw
  • Power drill or screwdriver
  • Table saw (or circular saw or hand saw)
  • Putty Knives
  • Pencil
  • Hammer
  • Goggles
  • Air compressor (optional)

The first step in building your sub box is to measure the size for the correct airspace. The subwoofer speaker pumps air to generate the lower frequency and create the desired thumping. This determined by the size of the subwoofer driver. Either using the size specifications off the equipment specifications sheet or by measuring the unit yourself. 

From these measurements, add 2 inches to the depth of your driver. Next, determine the minimum height of your box by measuring the frame diameter of you woofer. Once you have the desired dimensions, o consider the vehicle space you are willing to devote to the enclosure. This will also determine your subwoofer shape; square, rectangle or wedge. Alternatively, you could check the mounting template that was included in the owner’s manual.

Sub Size (inches)Box Volume (ft3)
6″0.36 – 0.48
8″0.72 – 0.96
10″1.2 – 1.8
12″2.4 – 3.6
15″6.0 – 10.8

Measure twice, cut once.

Step Two

When it comes to construction of your speaker box, most experts recommend using high-quality materials such as MDF (medium density fiberboard) because it keeps vibrations to a minimum. Building the actual cabinet will require some form of woodwork, that’s why most people prefer to buy the MDF and cut it at the store for a small fee.

If you’re cutting it yourself, make sure you use an electric table saw to guarantee flat cuts. Afterwards, sand the edges smooth for nice n’ easy assembly and clean joints.

The recommended standard is to use double thickness MDF for your front panels. Start by securing two pieces together of the same size. Use carpenter glue and sheet screws so it doesn’t budge. You can trace your subwoofer over the wood frame so that you have the exact dimensions you need to cut.

Use a drillpress to cut a hole along the border of the circle, where the enclosure hole will be, to create a starting point for the jigsaw to cut out the subwoofer opening. Cutout the circle and follow the exact same procedure to make a rectangular hole in the back panel for the terminal cup. Caulk the edge of the terminal to prevent scratching. 

Place the speaker in it’s designated hole to check if it fits properly. Mark the edges of the holes where screws will fasten the speaker to its new enclosure. Then fit the terminal cup in its new spot and seal up the edges using your silicone caulk.

 Step Three

Check the alignment of your enclosure panels; sides, top and bottom. Drill holes along the edges of the box and fill them with carpenters glue. After it settles, fasten drywall screws in the glued holes. Wipe off any excess glue.

Apply a generous amount of silicon caulk or apply glue to the joint lines to set up the frame. It takes at least an hour for the glue to dry. After it dries you can start adding screws. Take a power drill to pre-drill your screw holes, and drill in screws to connect the panels. You should have one screw for every 6 inches along the joint line.

Experts recommend that for the most effective bonding, leave the box aerated and undisturbed for 12-24 hours before proceeding to the last step.

Step Four

Hook up the speaker wires from the terminal port to the subwoofer. After all speaker wires are configured, and the connectors are in their appropriate holes, install the subwoofer in the enclosure and fasten it down with screws. Next, cover your enclosure with polyfill and fabric to keep resonance to a minimum. For the finishing touches, seal the subwoofer’s edges using rope caulk for an airtight fit. After a short period of testing to see if everything works out, install that bad boy in your vehicle; hook it up to the car stereo and enjoy the fruits of your hard labor.

For more information on subwoofer enclosures, check on Sonic Electronix’ YouTube page.