Box
Building
Each
type of sub requires it's own type of box. If a
sub is installed in a box larger or smaller than
what is supposed to, it will sound distorted/bad
and could be destroyed. Boxes can be built in many
shapes, but it is important that the box volume
is calculated accurately to achieve maximum performance.
Materials
A box MUST be very sturdy. Most common building
materials are 5/8" or thicker particle board or
medium density fiberboard. 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 very hard to work
with, and require several layers for a smooth finish.
Gluing,
Sealing
Glue should be used at all joints to fill any spaces.
Any spaces will degrade the performance of your
subs, not to mention the annoying noise air makes
when being pushed out of a small hole. On applying
the glue, let it cure for at least 24 hours before
mounting the subs. This is a precautionary mesure
to protect the rubbers used to make the subs from
the high fumes that some manufacturers glue products
have.
Holding
Joints Together
In connecting box joints, it is best to screw the
joints every four inches or so using 2" - 2-1/2"
screws. Pre-drill about 3/4" deep, so that screws
do not split the wood at the edges, especially when
working with particle/bashboard.
Should
I have a Box for Each Sub?
It is advised to have a separate chamber for each
sub. Even though not necessary, here are two reasons
why such a directive should be taken: First, if
one of the subs blows, then the volume of the box
will be "twice" as big for the one remaining working
sub. 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 make the
box more rigid.
Ports
Ports must be built into your box design to channel
out the air made by the sub's vibrations. If a pre-made
port is not available, the most common material
is PVC . PVC is very rigid, comes in different diameters.
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 a proper sealant (Evo Stick or even silicone
can be used).
Bracing
Boxes that are more than a foot in width or length
or height, should be braced so that the box becomes
more sturdy. This can be accomplished with a piece
of wood maybe 3 or 4 inches wide across the box).
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.
Damping/Filling
Damping increases subwoofer efficiency by dissipating
some energy that affects the sub, particularly the
voice coil. 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. Polyfill also "tricks" a sub into thinking
it is in a bigger box. Play around with different
amounts of polyfill until you get the desired results.
Making
it look professional
Make the box surface free from holes and spaces
by adding wood fill. If you decide to paint the
box, then you should apply primer first. Carpet
or Vinyl padding is the best covering to use since
they easily cover any outer blemishes on teh box
and give the box a 'smooth' outlook. Be carefull
when cutting the vinyl or carpet since such cutters
tend to be very sharp. Cut a piece of carpet (or
vinyl) big enough to cover the whole box. Apply
adhesive to both box and carpet (EvoStick works
great). Wait about a minute and place the fabric
over the wood. For the best 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 preferabke heavy duty staples
that can penetrate the box, to hold the fabric at
the ends. NOTE: Do not cover each panel of
the box before mounting it together since it would
be impossible to find any 'leaks' that may exist
in the box design much less fill these leaks.
