How to Design and Build a Subwoofer Enclosure

When you are looking into how to design and build a subwoofer enclosure, there are several things you need to take into consideration. The correct design of a subwoofer enclosure is not as just a box you put the woofer into - it should also take into account the speaker’s size, shape, and volume, as well as where it will be placed.

There are two types of box designs: vented and sealed.

The vented enclosure—or ported enclosure—is a more efficient choice. These boxes channel the sound waves from the speaker from both the front and rear and help with making better sound by providing a lower bass reproduction and a low distortion level. However, these systems are also much more complex to build than the sealed enclosures.

Sealed subwoofer enclosures are simply an air-tight enclosure built to improve and enhance the speaker’s performance. These boxes separate the sound waves in the front from in the back. When these waves are not separated they tend to cancel each other out. The sealed box is the most popular choice due to excellent dampening, power handling, and ease of design.

This article will go through the steps to create a sealed subwoofer enclosure.

Step 1 — Volume of Intended Application

When designing a subwoofer enclosure, the first thing you need to do is measure the space you will be placing the box. The space you want to put the box in will greatly narrow down the choices. For instance, a 12-inch subwoofer typically needs 2-3 cubic feet of interior space, but you may need to add a bit of extra space to ensure an easy, but snug, fit. Therefore, the box will need to be 2.5-3.5 cubic feet. Below please find the speaker/driver size to enclosure volumes for your equipment.

• 6-inch — 0.3-0.4 cubic feet
• 8-inch — 0.6-0.8 cubic feet
• 10-inch — 1.0-1.5 cubic feet
• 12-inch — 2.0-3.0 cubic feet
• 15-inch — 5.0-9.0 cubic feet

Step 2 — Decide the Shape

The next step is to decide what shape to use and determine the internal volume of that shape. You can then get the best sound and also to be sure that you have the correct internal volume for your speaker. Below are the equations for the most popular shapes to help to calculate the internal volume needed.

First, calculate the area:

• Rectangle: width x length=area
• Triangle: widthx1/2 length= area
• Circle: radius x radius 3.14= area

Once you have the area, you can find the volume:

• Rectangle: depth x area=volume
• Triangle: depth x area= volume
• Circle: length x area= volume

Note: 1,728 cubic inches= 1 cubic foot

Step 3 - Choose your Material

There are only two types of materials you should be using: fiberboard and plywood. Fiberboard will minimize panel vibrations due to its density, which really makes it the better choice. However, plywood is a good option if for some reason you cannot get fiberboard. A solid 5/8-inch thick piece will work for smaller volume applications of up to 2 cubic feet; for larger applications, go with a ¾-inch thickness.

Step 4 - Build

Cut all of the pieces to the correct sizes for the interior volume you have chosen. Cut the holes for the speakers. Once everything is cut, do a mock-up of the box before you build it to make sure everything has a nice tight fit.

Below are the steps necessary to build the subwoofer enclosure:

1. Run a bead of carpenter’s glue along one edge.
2. Do not install the part with the holes for the speakers yet.
3. Once you have an open-end (whatever shape you chose) place a bead of silicone all along the inside edges of the box, tube, triangle to insure a sealed environment.
4. Add the “face” to the rest of the box.
5. Decorate your box with carpeting. This can be attached using a spray adhesive.
6. Wait for the glue and sealant to dry completely before going any further. It is recommended to wait about 12 hours.
7. Screw the speakers into the new enclosure and you are ready to hook it up and try it out.

Customizing Your Subwoofer Enclosures