Guide Speakers

Building a Car Subwoofer Box from Scratch: 9 Steps

Written by Edwards

In this guide, we will be discussing in detail how to build a subwoofer box from start to finish. We also bring you all the tools and materials you need to build a unique subwoofer box that meets all your needs.

If you are on the budget, you can choose the best cheap/budget subwoofer and proceed with the steps below. Keep in mind that it should not take you more than a few hours to complete this job.

Tools and Materials You Will Need

  • Jigsaw
  • Saw
  • Pencil
  • Box cutter
  • Razor
  • Tape measure
  • Carpet
  • drill
  • 3/4″ MDF board
  • 2″ drywall screws
  • Panhead screws
  • Carpenter’s glue
  • Silicon caulk
  • Rope caulk
  • Speaker terminal cup 


Steps for Building a Subwoofer Box

  • Step 1: Choosing your SubwooferThere are many powered car subwoofers to choose from on the market. Some of the best car speakers are Sony, Alpine, Kenwood, Pioneer, and more. Depending on the brand you choose, you can expect each of the subs to have different specifications. All subwoofer brands offer different models, but the one constant thing about all subwoofers is their size categories. The 12-inch subwoofer is the most popular size among all brands while the 8-inch subwoofer as the smallest and the 15-inch subwoofer is the largest among all brands.
  • Step 2: Determining The Ideal Location of the Subwoofer Box Designing a subwoofer box is dependent on many factors least of which the placing subwoofer. For instance, a car’s trunk has a lot of space, and you can go wild with the design of the subwoofer box unlike underneath the front seats. For an under seat subwoofer, a cuboid box is ideal as it saves a lot of space while the trunk can comfortably accommodate a much more massive cube box or a wedge box. All in all, the trunk is the most preferred location for most people so that they can have space to mount a car amplifier underneath the front seat.
  • Step 3: Designing the BoxCar subwoofers are not like home subwoofers which come complete. And as such, there are many things you need to take into consideration when designing what’s subwoofer box. Let’s look at them below;
  • 1. Determining the Shape of the BoxThe first step is sketching out the shape of the box. There are different shapes you can pick, but a cube, cuboid and a wedge are the easiest to construct.
  • 2. Determining the Box’s Interior Dimensions and VolumeKeep in mind that most modern subwoofers don’t require huge boxes as with the traditional ones. For instance, a standard 10-inch subwoofer requires an internal volume of about 0.6 and 1.25-sq. Feet so let your subwoofer’s specifications guide you through this step.
  • 3. Calculating the Internal DimensionsGetting the correct internal dimensions you need to determine the right length, height, and width with some mathematics. For instance, if you bought a 10-inch sub and wished to build a cube box that falls within a volume range of about 0.6 and 1.25-sq. Feet, you will need to do the following;
  • Remember that a cube box has all sides equal and is easier to construct.Work with inches as they are easier to read in a tape measure
  • Convert the 0.6 and 1.25-sq. Feet range to square inches → (1-sq. foot = 1728-sq. inches) therefore, you will need a cube box with a volume that varies between 1036.8 and 2160-sq. Inches.
  • Next, find the cube root to determine the interior dimensions;
  • A. If you want the smallest possible box (1036.8-sq. inches) to save space, it should have dimensions measuring 10.12-inches all through
  • B. A large box (2160-sq. inches) should have aspects of 12.93-inches all through
  • 4. Calculating the External Dimensions If you are using a ¾-inch MDF, you need to account for the thickness of the MDF board to get the correct dimensions. If you don’t mind for the board’s width, you will not achieve the volume you intend to use. Here is how to factor in the thickness of the MDF board.
  • Add 3/4-inches on both sides or 1.5-inches (3/4-inches x 2 = 1.5-inches) when measuring the length
  • I. The smallest box should have dimension measuring 11.62-inches all through (10.12-inches + 1.5-inches)
  • II. The largest box should have dimensions of 14.43-inches all through (12.93-inches + 1.5-inches)
  • Step 4: Preparing and Cutting the MDF BoardsNow that you have the necessary measurements, it is time to mark your MDF board for cutting. Since we’re making a cube box and all sides have equal sizes, use your tape measure and mark all the cut points with your pencil Next, use your saw or table saw to cut out the pieces of board you will use. Cut a total of six pieces for the front, back, top and bottom faces as well as 2 for the sides. Cut out seven pieces of MDF if you are planning to use a double MDF placement on the front face for maximum strength
  • Step 5: Mark and Cut Out the Front Face Where You Will Mount the SubUse a compass or a divider to mark out the subwoofer’s cut out on the front side MDF board. Next, take your jigsaw and carefully cut out the circle you made as this is where you will install a subwoofer. If you are planning to integrate two subwoofers in the box, ensure you also mark and cut out the back face of the MDF board. If you don’t have the tools, you can visit a local woodworks store to cut the pieces for you for a small fee.
  • Step 6: Installing the Sub’s Terminal CupA terminal cup is important to wire a subwoofer so mark and cut a rectangular hole at the back of the box to fit the terminal cup. If you have integrated two subs in one box, install the terminal cup on either side of the box.
  • Step 7: Fastening the Pieces TogetherFor this step, use your carpenter’s glue or silicone seal the pieces together then take your drywall screws to fasten the pieces together. The silicon will help keep the box airtight for better quality.
  • Step 8: Installing the Sub into the BoxInsert the best car subwoofer you chose for yourself then mark the pre-drill holes in the box. Next, take out the speaker and connect the wires from the terminal cup to the subwoofer. Lastly, insert the sub back to its place and tighten the screws to hold it in place securely.
  • Step 9: FinishingAt this point, your sub is ready for use, but you can choose to add some personal touch to it. If you don’t like the wooden finish, you can cover the box with some carpeting that matches your car’s interior. You can also cover the box with some custom wrapping paper if you’re feeling adventurous and vibrant. You can now start enjoying your favorite music in style.
  • You can read more on What Speakers Can Fit My Car, and how to install car speakers from our other guide.


  1. crutchfield, How to build a subwoofer box, North American retailer specializing in a wide range of electronics, including mobile audio and video equipment
  2. CarAudioFabrication, How to Design a Subwoofer Box – Design Software and the Math!, Step by step tutorials on how to design and build Car Audio Systems
  3. WikiHow, How to Measure a Subwoofer Box, Learn how to do anything with wikiHow, the world’s most popular how-to website
  4. Instructables, Building Simple Box, specializing in user-created and uploaded do-it-yourself projects

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