Well my second sub project has officially started. Sad part is neither of the subs are for me. Two identical subs are being made. One for my parents, one for my roommate. Going to be Dayton DVC12" in 125L sonotubes tuned to 20hz with 4" flared ports. Anyways, started today after supper and the only thing accomplished besides getting all the mdf cut into 20" squares and glued into 1.5" thick pieces was the construction of significantly better circle jigs than were used in building my first sub. Here are links to three more images: Close up of pivot point from top. Close up of pivot point from bottom. Close up of router mounting holes. These were inspired by Brian Steeves. Yes we drilled a hole in the middle of the 1/4" bolt to get that pin there The wood piece has a grove that fits in the top slot so that it can't rotate at all. Its' purpose is to be a fixed point from which distance reference marks can be made. These along with an up cutting spiral bit should made endcap construction much easier this time around.