Pixelhugger's progress motivated me to get working on this cab again. It was a gorgeous day out so I made the speaker grill. I made it out of 1/2" MDF that is held on with really powerful rare earth magnets.
First I screwed in some temporary router guides and cut the speaker holes.
Then I rounded it over and spray painted it black.
Following Pixelhugger's example, I held the frame in position and drilled four small pilot holes to be guides for drilling the retainer magnet holes. The magnets were epoxied into holes that were already a snug fit. Here is a magnet in the cabinet frame:
I stretched the grille cloth over and secured with staples and hobby glue. Everything came out great: