This is the second attempt at making a nice MDF box for my 10" subwoofer. See subwoofer v1 for info on the power supply.
Ported subwoofer enclosures are a bit more complicated than sealed enclosures because the port itself will have a resonant frequency. Depending on the listener, you may want to tune your port to a frequency you like. Because the driver im using is lower end, I ended up tuning the port close to the inherent peak response frequency of 40hz. This is a bit higher than some people like, as most higher end sub-users will tune to 35hz, 32hz, or even 30hz.
For calculating the port width, as well as the general dimensions of the box, I used the RE Box calculator, available at http://reaudio.com/box.php
This calculator also provided me with the exact dimentions of the MDF pieces I would have to cut.
I used two quarter-sheets of MDF for this build
I measured the cuts on the boards and used a table saw for constant sized walls. Make sure to label every piece to make assembly easier later.
After all the pieces were cut, I sanded the edges and began preparing to glue everything together.
For this I used woodglue and a nail gun (actually called a brad gun) and 1.5 inch brads (twice the thickness of the wood). The main reason for the brads is to hold the box together while the glue sets, but they also add structual integrity to the build.
Starting with the base, I nailed and glued each piece into place.
The top plate should be the last to go on, so nail everything in from the bottom first. The inner port wall, which consists of two plates, should be nailed in first so that it is easy to nail them together, as it would be impossible to nail after the outer walls were put on.
Sand all of the corners that are inside the box to ease airflow inside the box. You can also add small 45 degree cuts to wedge in the corners to help reduce corner turbulence. Small things like this help eliminate unwanted noise and increase clarity.
As for the actual sub mounting plate, this can be done three ways.
Measure out where the center of the cirlce is and cut it out. If you have to choose between cutting the hole too small or too big, choose too small. It is easy to cut more MDF if needed, but it is extremely difficult to return MDF that has already been cut away.
After all the internal plates have been nailed and glued to the bottom plate, it is time to caulk all the joints. Try to get as good an air seal as possible. As for caulking the top plate, just measure as best as you can and precaulk the top plate before putting it down. Then nail and glue the top plate. For the inner port walls, use a ruler to measure where they are in the box and nail from the top. After this is done, let the box dry for a couple hours before stressing the joints.
For the connectors I just used some misc plugs I found lying around, but you can also just wire the sub through the port...
For wiring, see subwoofer v1....
This box sees a great improvement in volume of low-frequencies, and the quality is similar, but slightly lower.
For comparison, here are the tables for Sealed, Ported, and Bandpass enclosures
^Don't quote me on that though ;)