i made these speaker inclosures for the 58 chevy truck in my avatar a while back.
here's how to cut speaker rings on my cheap a$$ router table;
i see a lot of people using a jigsaw to cut rings and do a poor job at it. yes you can use a jigsaw. you realy need a router to round over. my 1978 router burned up, i bought this one at home depot for $49. i don't like plunge router, never did, never had a need for one.
i'll show you how to make this speaker ring. these are for my kick panels.
when i do my layout, i draw everything full scale on the mdf. i drill a 1/8" hole in the center of each ring. then i drill 1/4" holes where i want to route a groove. there are 2 sets of rings on this board. the top ring and the bottom ring. i'm doing a reccessed ring for the speaker.
first you want to cut the outside of the ring and then the inside of the ring. if you reverse the order and cut the inside first, then you have no pivot to cut the outside. place the outside hole over the 1/4" spiral bit and use a screw thru the center hole to screw it down the the table.
cut to the marks
my photo of cutting the inside did work, so i move on. place the big ring on the outer hole, screw down the center and cut to the mark.
then place the inside hole over the bit and cut 90% around the hole.
you can cut all the way, but you risk digging in with the router bit. tape the cutout securely in place
and then finish the cut
peal the tape and you have this
i used a bandsaw to finish the arc connecting the 2 rings, then sanded all the edges smooth to get rid of machine marks and did a test fit
then i used a 3/8" roundover bit to dress the inside radius and 1/4" roundover bit to do the outside radius, raising the bit to get a 1/8" rabbit for stapling the cloth on.
buy a good cabide spiral cut bit. it will pay you back in labor savings. i had a tool steel straight cut bit and had to make 3 passes to cut each ring. these spiral cut bits are sweet!
yes, there are 10 ways to cut rings. this is how i do it.