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4.5 How do I build an enclosure? [AO]


This article is from the Car Audio FAQ, by Ian D. Bjorhovde (ianbjor@mobileaudio.com) with numerous contributions by others.

4.5 How do I build an enclosure? [AO]

These instructions are for building a first order (sealed) subwoofer
enclosure. Building ported or bandpass boxes is more difficult, and
those designs are less forgiving of mistakes. These instructions apply
for all box designs, but be sure of the measurements before you make
your cut. Building your own enclosure can save you a lot of money, but
only if you don't need to buy all of your materials twice because of

You will need:

I only use MDF (see Section 4.6), but others have reported
success using other hardwoods like birch and oak. Do not use
plywood - it's far to flexible and porous. Use a minimum of 3/4"
wood - flexing sub enclosures lose precious energy!

For one inch wood use #8 2 inch wood screws. For 3/4 inch wood use
#8 1 3/4 inch screws. Double grip Drywall screws also work well.

I use "Liquid Nails" which comes in a caulk tube or a bucket, but
any paste type of adhesive will work. Spray adhesives will not

*Silicone sealant*
White, brown, clear, caulk tube, or squeeze bottle, it doesn't
matter. Make sure you don't get silicone lubricant (which comes
in a spray can)!

*Terminals/Terminal Cup*
To allow easy connections from your amp.

Besides these materials you will need several tools:

*Table saw or radial arm saw*
I use a radial arm saw, just because it's a little easier and
accurate, but a table saw will work also. You can use a circular
saw, but be very careful to make your cuts straight.

*Jig saw*
For cutting your speaker hole.

You will also need a 1/8" drill bit, a screwdriver bit, and a
countersinking bit.

To mark your cuts, make notes, etc.

*Measuring tape*

*Safety Goggles*

*Face Mask*
Breathing MDF dust has not been proven to cause health-related
problems, but hang around with with a few installers at your local
shop for an afternoon and you'll see why you need a face mask. :-)

Start by marking the cuts you need to make on your wood. Double check
your math, and your measurements.

Use the table or radial arm saw to cut your wood. When you're done you
should have six pieces of wood which fit together tightly to form a box.

At this point you will need to trace the cut out for your subwoofer onto
the front of the box. Remember that if you have a 10 inch subwoofer you
do NOT want a 10 inch cutout. The 10 inch measurement is from the
outside of the mounting ring. The actual cutout diameter should be with
your instructions. Transfer the proper sized circle onto the sub box
and cut it out with the jig saw. If you have trouble starting cuts with
a jig saw, drill a 1/2" hole in the wood inside the circle. You can
drop your blade into the hole and then cut out to the edge of the circle
and around.

After you have cut out your mounting hole you will need to cut out a
square on one of the sides for your terminal cup. Transfer the proper
size rectangle onto the wood and cut it out with the jig saw.

Now you are ready to start assembling the enclosure. Choose one of the
ends, and one of the sides. Apply a bead of adhesive along the edge of
the end piece. Affix it to the edge of the bottom piece. Flip it over
(have a friend hold the other end and hold the end in place,) and screw
the edge to the end. Use one screw at each corner and then one more
screw about every 8 inches. Drill a pilot hole with your 1/8" drill
bit, then drill a countersink with your countersinking bit. Finally,
drive the screw in. Make sure that you don't strip the hole.

Repeat the above procedure with the other end. You should now have the
two ends connected to one side. Affix the other three sides the same

Finally, you'll want to seal the insides of the box with silicone. Apply
a bead of silicone across all the inside edges and around the terminal

Allow the box to dry over night and then place your speaker into the
hole. Screw it down and you're done!


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