I am the Dad. I thought it would be good for me to add a few things Jeremymeff left out of the process for those who want to do it yourselves.
1. Rabbeting the sides of the box is a much tighter, longer lasting design, but it requires foresight and a set of drawings. Rabbeting
is when a 3/8" x 3/8" piece is cut along the edge of both adjoining edges so they nest together. This creates 3/8" more surface area, for the glue to attach the pieces. We also added counter-sunk grabber screws to strengthen the joint and hold it together until the glue set. We used regular wood glue.
2. Unless you have a mind like Stephen Hawkins, you must draw out your box, with details of the joints in order to get the measurements right. Below are some simple sketches we drew to avoid confusion.
This helped us remember what we were actually building. The numbers at the bottom were the cut list for the sides cut from 4'x8' MDF. 3-21"x21" were for the face, back and backer for the face. The 4-21"x18" were for the sides. These were just rough cuts and we then trimmed down the actual pieces as needed.
This is the detail of which sides needed to be rabbeted.
This showed how the pieces fit together. We purposely cut the rabbet deeper on one side than the other so there was an overhang of 1/16". We cut this off with a flush-cut router bit after assembly and touched it up with a palm sander. It made the box perfectly smooth on all corners.
Each joint was glued liberally, then we drilled pilot holes that were counter-sunk and inserted grabber screws. We also filled the counter-sunk screw heads with filler and sanded them to make a smooth, solid backing for the veneer. The veneer is so thin, any voids could cause the veneer to divot if hit hard.
Using the circle jig to cut the holes was a sweet deal. It is important to brace across the back side of the hole you are cutting BEFORE you cut it out. The router jig pivots on the center of the hole you are removing, so unless it is still connected to the box after you complete the cut, it is like cutting off the branch you are sitting on. Makes a real mess.
We had concerns about the face piece being strong enough to hold the speaker since we only had about 1 1/2" of material left around the edge of the hole and because we also counter-sunk the rim of the speaker, it left only 1/2" of material to bolt the speaker with. We choose to cut another piece of MDF and screwed it to back the face so we now had 1 1/4" of bulk to bolt to. This was cut to slide inside the box when we attached the face piece. It was glued and screwed.
This detail showed how the backing for the face piece fit together along with the rabbet for the speaker flange.
We also inserted T-nuts in the back side of the holes so we could bolt the speaker and amp on with machine screws rather than wood screws or nuts and bolts. Now is it easy to unscrew the bolts and remove the speaker or amp any number of times without damaging the holes or loosing nuts.
Applying the veneer was not that difficult. The important thing to remember is that once you coat both pieces and allow them to dry, if they touch, they stay there, whether it is where you want it or not. We used 2 pieces of parchment paper, one on each half, to separate the veneer and the box. It didn't stick to either surface. We could then move the veneer around until it lined up perfectly, (hanging over the edge 1/8" all the way around the box). We pulled out one piece of parchment and pressed that side down, then pulled out the other parchment and pressed the balance down. It was very slick and easy. The parchment paper is the kind used for baking and can be purchased at most any grocery store. You can also use visqueen, plastic, wax paper or any other semi-slick material. I would recommend using 2 smaller pieces rather than one large piece because it makes the job easier to remove half at a time.
The veneer is VERY thin, only about 1/16" thick. Avoid using a power sander unless you are very, very good or very, very stupid. You can ruin hours of work in about 10 seconds.
The slot for the grill cloth spline was only 1/8" thick and 1/4" deep. The screen spline
we used can be purchased at Home Depot or Lowes. There is also a spline roller tool
that makes it a snap to install. The corners were cut on a mitre and spot glued to hold them in place.