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:


