The Start of the Speaker Area
Start with a 20" wide x 12" deep board (A). You will be beveling one end, the end that will receive the marquee retainer. Take the board to the table saw. Set the bevel to 30 degrees and rip off just the end of the board (see B). You should end up with a board that is about 12" wide at its widest. Because a portion of the board will be hidden by the monitor glass, its fine if you end up with a narrower board than this. Just try to keep it over 11 inches.
Note- We did not cut out the speaker holes yet due to not having decided which ones to go with. Because we will be disassembling the cabinet to paint, we'll just cut out the holes later on. The details of this process are later on in the document. If you have your speakers already, feel free to cut out the holes prior to mounting.
Next, fit it into its spot and prepare to pop some screws into it from
the inside. I used a clamp to hold the board firmly in place (see
C). This makes your life easier and allows for fine adjustments to
its position before your screw it into place. Once you get it just
right, screw 4 screws into it through the pre-dilled holes in the
ledgers. It should end up looking like D through F.
Next up is the upper rear board.