This weeks update. I had to get the back finished before moving to the front, because it won't be so simple to lay them down with the back up once the moldings are on the front. I did a test fit on the removable panel, and that was fine until I tried to remove it, and found that it was too tigt of a fit, and it didn't want to come out. It was OK, because I could stand it up and push it back out from the front. Of course that won't work later once the horns are installed. I needed to enlarge the opening a little bit. And I decided I need a handle. I routed out a hole half way through, then moved in a quarter inch in height, and routed all the way through. Those pencil lines are where I clamped boards to fence in the router, for the horizontal cuts. I ended up freehanding the vertical cuts, then cleaned up the holes a bit with a wood chisel. The wide part goes on the inside, to make the place to grip. I need to glue a piece of wood inside to close up the hole, but it's a no cost method to add a handle.
Then I laid out and drilled holes to fasten that back section and put in hurricane nuts. I want a little overboard with the number of screws. Half this number might be enough.
On to the front. I added the moldings along the edges of the front. These are just made from walnut boards cut to size on the table saw. Then the fronts were sawed at a slight angle. This is supposed to match the curvature of the horn at the edge. It should minimize any diffraction there, the grill frame will match the same profile. It wasn't easy to install these, the boards weren't very flat or straight when I started with them, and so the resulting moldings are not very flat or straight either. But with some struggle, they are securely glued into place, with some variation from flush along the sides. I may round the edges on these, they are sharp for now.
I made the length the same as the plan for the outside dimension of the grille cloth frames.
Next was a strip of veneer that covers the bottom where the grille cloth ends. You can see here that I wanted to toughen up the bottom of the cabinets as I'm not veneering there. I painted it with a thin coat of wood glue.