Don Mascali
03-25-2006, 11:56 AM
I just finished doing the circle cutouts on the front baffle boards of my new speaker project. I thought I would do a “how to” for those who may be new to this hobby and save them some time climbing the learning curve.
First, this may sound like an “Info-mercial” for the Jasper Circle Guide. It is! I have built quite a few speakers using a jig saw to cut the holes. Man did I waste time and energy. This little marvel will help you cut perfect holes, 2 ¼” to 18 3/16” with ease. That covers every driver JBL makes and if they don’t make it you don’t need it, right?
I had to cut a 12”, a 15” and two 4 ½” holes in each of four baffles. I hate to think about how long and how ragged looking a job that would have been with out the guide. I purchased the guide from Parts Express for under $40.00 and I feel like it paid for itself in reduced frustration alone.
The guide attaches to a standard “Plunge Router”. Mine is a Porter Cable #1001-T2 and I used a ¼” round carbide plunge bit, Porter Cable #2880201. Any brand will do of course but you should use a carbide bit. MDF and particle board will make short work of a high speed steel bit.
You start off by laying out the center of the cut out and drilling a 9/64” hole. The center pivot pin of the guide is 1/8” and I found a little larger hole worked better as the pivot pin stuck in the hole with an 1/8” hole. I used the exact measurement from the JBL .pdf documents. The marks are very well calibrated for the ¼” bit and are laid out by 1/16”. You insert the pin in the marked hole on the guide plate for the desired size and then insert the router and guide with the pivot pin in the hole drilled as center. When using ¾” material I set the plunge guide for ½” and did the front by turning the router clock wise 360 degrees around the pivot pin. Then turn the piece over and repeat. This leaves a nice edge on both sides, where trying to do the entire cut was problematic. It helps to keep another board under the cut as the puck wants to move or fall out when you get to the end of the cut. Having the support underneath gives you more control.
A word here about hearing protection, please use some! Routers scream at a high frequency and nothing will make your tweeters useless quicker if you aren’t protected.
I hope this proves useful and if any of the more experienced builders have something to add, please do so.
Good luck,
Don M
First, this may sound like an “Info-mercial” for the Jasper Circle Guide. It is! I have built quite a few speakers using a jig saw to cut the holes. Man did I waste time and energy. This little marvel will help you cut perfect holes, 2 ¼” to 18 3/16” with ease. That covers every driver JBL makes and if they don’t make it you don’t need it, right?
I had to cut a 12”, a 15” and two 4 ½” holes in each of four baffles. I hate to think about how long and how ragged looking a job that would have been with out the guide. I purchased the guide from Parts Express for under $40.00 and I feel like it paid for itself in reduced frustration alone.
The guide attaches to a standard “Plunge Router”. Mine is a Porter Cable #1001-T2 and I used a ¼” round carbide plunge bit, Porter Cable #2880201. Any brand will do of course but you should use a carbide bit. MDF and particle board will make short work of a high speed steel bit.
You start off by laying out the center of the cut out and drilling a 9/64” hole. The center pivot pin of the guide is 1/8” and I found a little larger hole worked better as the pivot pin stuck in the hole with an 1/8” hole. I used the exact measurement from the JBL .pdf documents. The marks are very well calibrated for the ¼” bit and are laid out by 1/16”. You insert the pin in the marked hole on the guide plate for the desired size and then insert the router and guide with the pivot pin in the hole drilled as center. When using ¾” material I set the plunge guide for ½” and did the front by turning the router clock wise 360 degrees around the pivot pin. Then turn the piece over and repeat. This leaves a nice edge on both sides, where trying to do the entire cut was problematic. It helps to keep another board under the cut as the puck wants to move or fall out when you get to the end of the cut. Having the support underneath gives you more control.
A word here about hearing protection, please use some! Routers scream at a high frequency and nothing will make your tweeters useless quicker if you aren’t protected.
I hope this proves useful and if any of the more experienced builders have something to add, please do so.
Good luck,
Don M