Basic Box Building Information.
Check with manufacturer or
dealer for appropriate box volume and design. Some subs can't be used in
certain types of boxes, and have very small tolerances for box volume
errors. If a sub is installed in a box larger or smaller than what is
supposed to, it will sound bad and could be destroyed. Boxes can be built
in any shape, but it is difficult to calculate volume for complex
A box has to be very rigid. Most common building
materials are 5/8" or thicker particle board or medium density
If building a box with Plexiglas, do not use anything less
that 1/2 inch thick.
A common material used to mold complex shaped boxes is
fiberglass, but it is a real pain to work with, and several layers need to be
applied for a solid finish.
Use glue at all joints (cheapest and most used product is
Liquid Nails). Make sure there are no holes. Any leaks will
degrade the performance of your subs, not to mention the annoying noise air
makes when being pushed out of a small hole.
Let glue cure for at least 24 hours before mounting the
woofers. The fumes of some products will eat up rubber and other
materials subs are made of.
Holding Joints Together
Screw joints (use 2" - 2-1/2" screws) every
four inches or so. Pre-drill about 3/4" deep, so that screws do not split the
wood at the edges, especially when working with
A box for Each Sub?
Even though it is not necessary to have two separate
chambers for two subs, it is best to take this approach for two reasons:
First, if one of the subs dies, then the volume of the box will be "twice" as
big, as seen by the sub that is still working. This could cause problems
and even damage the other sub. The second reason is bracing.
building a box with a divider in the middle will be much
There are several way to build ports. If a pre-made
port is not available, the most common material is PVC tubing. PVC
tubing is very rigid, comes in different diameters, and is easily found at any
Cut the tubing at the desired length. Consider the
volume the port takes up when calculating the box volume. Cut a hole in
the box. Make sure the hole is as perfect as possible to minimize gaps
between the box and the tube. A couple wood braces can be added for
screwing the port top the box. Seal the gaps using plenty of Liquid
Nails or similar product.
Boxes that are more than a foot on width or length or
height, should be braced (use a piece of wood maybe 3 or 4 inches wide across
the box, so that box does not flex). It is a good idea to put wood
blocks on the corners for reinforcement. Always consider that blocks, braces,
neon lights, etc. inside a box take up space and should be accounted for when
calculating internal volume.
It is advisable to put damping material inside a box.
Pillow polyfill and fiberglass insulation are common, though polyfill
is a lot easier on your skin. This increases subwoofer efficiency by
dissipating some energy that affects the sub, particularly the voice
coil. Polyfill also "fools" a sub into thinking it is in a bigger
box. Play around with different amounts of polyfill until you get the
Finishing the Box
Add wood filler to holes and sand the box to make a smooth
surface. If you are painting the box, It is a good idea to apply primer
under the paint.
It is not necessary to sand the box if you are using
carpet or padding under vinyl, since the thickness of the material will cover
any small imperfections. The best way to cut carpet or vinyl is with a
good quality carpet knife. Blades wear out pretty quickly, so buy a
handful. Cut a piece of carpet (or vinyl) big enough to cover the whole
box. Apply adhesive to both box and carpet (spray 3M adhesive 77 or 90
works great). Wait about a minute and place the fabric over the wood.
For a good fit, stretch the fabric when applying it. The fabric should
wrap around and end in a place of the box that will not be seen. Do one
side at a time, cutting excess carpet. If possible, add staples to hold
the fabric at the ends.