I dont know if this one has been posted yet.
To cut out holes for subs using a router.
Determine the size hole you want to cut out.
Get a piece of wood, a scrap piece of mdf works great, make sure it is wide enough so the router isnt wobbling on it.
Drill a hole to accept the router bit (a straight bit) you will also need a set of guide bushings.
Predrill a hole for the nail in the circle jig and nail it in the middle of where you want the hole to be, put the router in and start cutting. Make shallow cuts like a 1/4 inch or so at a time so not to burn up the bit, and to make the cutting easier.
Measure twice, cut once.
Tip 2. For those who like to paint their enclosures and want a cool look and a strong hold, You could try a dovetail joint. This would involve a router and a dovetail jig.