Building a subwoofer presumes that the loudspeaker/driver to be used has been chosen. The loudspeaker and its Thiele/Small parameters dictate everything about constructing the box. A subwoofer box should be made from the densest material possible.
The Benefits of Plywood
The most famous and trend-setting speaker of all, the Voice of the Theater, employed a cabinet of 3/4-inch plywood with a 15-inch woofer to deliver revolutionary sound reproduction for more than 40 years. Therefore, 3/4-inch plywood on all surfaces of any enclosure certainly suffices for any do-it-yourselfer.
Cut panels to size yourself or buy a sheet of plywood from Home Depot or Lowe's, and have them cut it to your specifications. Use bracing and insulation to aid rigidity and damping of the cabinets, respectively. You can make square ports for a ported sub design out of the plywood, too.
Plywood has the benefit of being lighter than other enclosure materials, and you can easily drill it. Remember that the cabinet is slightly larger in a ported design than a sealed design, to account for the addition of the port.
The Benefits of MDF
Medium-density fiberboard (MDF) is both denser and stiffer than plywood. Both of these qualities make it a preferred material for subwoofer building among today's DIY aficionados because of the massive amounts of air that must be moved to generate low frequencies. MDF is also heavier and more expensive than plywood.
It also throws off a lot of dust when sawing and needs plywood backing if any T-nuts are needed in construction.
The Benefits of Sonotube
The preferred material for building cylindrical subs is Sonotube, a heavy cardboard frame for pouring cylindrical concrete. It is obviously a very sturdy substance, making it ideal for the "walls" of a cylindrical sub. Round subs, in addition to being a different aesthetic choice, can be used as corner tables and may be less obtrusive than big boxes. More importantly, this shape avoids many of the tuning complexities that are part of a rectangular ported design. Plywood can be used for the top and bottom of the cylinder, although MDF is again the preferred choice of many subwoofer builders.
Subwoofer Box Construction Basics
All enclosure materials can be found at Home Depot, Lowe's or any other building products store. Cut the panels yourself if you have a power saw or table saw; the stores cut materials to size for a small fee.
Test-fit all panels to ensure correct fitting before doing any gluing. Small adjustments that might need to be made are much more difficult once the box is being glued.
Top and bottom panels should be inset between sides, so their dimensions are the interior dimensions of the enclosure. An interior brace is the same size and is used within the box to maximize rigidity and minimize vibrations.
Use screws with silicon caulk applied around their diameter to ensure air-tightness at all connection points, and caulk all inside joints as well. Allow the cabinet to dry for 24 hours before installing the loudspeaker, since caulk fumes that can erode speaker surrounds must dissipate.
The Most Famous Subwoofer Box
Back before any of us were making speakers, Altec-Lansing, a company formed from ex-Bell Labs employees, put out a revolutionary movie theater speaker named Voice of the Theater. James B. Lansing of JBL fame designed part of this ported woofer with high-frequency horn design that debuted in 1945. If anything attests to the validity of plywood as a material, it's Voice of the Theater. The same thing goes for ported designs for home theaters. Today, the present-day Altec corporation has resurrected the Voice of the Theater speakers at $5800 each, making it a high standard of another sort for a certain niche of audiophiles.
Home theater speakers can be installed in a variety of ways, but there are guidelines that must be followed to create the proper listening environment.
Choosing great home theater speakers isn't too hard to do, if you know what specs to consider. Times were when a pair of speakers were all you needed for great stereo sound. That won't cut it for home theater, though, where 5.1 sound is a minimum and newer, more exotic arrangements can have you putting up to eight speakers around your room.
Home theaters are fabulous because they allow you to experience the thrill and excitement that comes from watching movies at the cinema in the privacy and comfort of your own home. By making smart, informed decisions when you are setting up and buying equipment for your home theater you will have a fun, relaxing and enjoyable space for years to come.