Just a FYI to the speaker builders or future speaker builders. I had a couple Jasper circle jigs. I recently upgraded my router to this amazing porter cable 7539. I just went to do some wood work and found that my Jasper circle jigs are now useless as the holes don't match up. I was pretty irritated as Jasper does not even have an adapter I called them ( now i have a bunch of jigs that I cant use). I search around and found something called the 'Router Buddy Circle Jig' you can Google it ( they sell at PE as well). It is much better in my opinion. Trying to get the right pin into the right hole on the jasper was a pain especially when you were working underneath the router base. The router buddy makes this much easier. You only need a digital caliper to measure the distance and set what you need. Very nice indeed. Just a suggestion to anyone going to buy a circle jig. Everyone raves about the Jaspers but I really like the router buddy.