I'm building my own speaker box, with a 15" sub and (4) 4" speakers. I have a hole saw for the 4" holes . . . not sure how one goes about cutting a perfectly round 15" hole.
I have a jigsaw, but doubt my hand is steady/precise enough to not make a mess of it.
Thx . . .

There are circle cutting attachments for power jig saws. They basically just consist of an arm that attaches to the sole plate of the saw and have some sort of peg or pin that gets driven into the center of the hole being cut out. Use a relatively narrow blade to make the curved cut, drill a hole big enough to put the blade through just inside the cutting line. You can probably piece together something similar if you don't want to get the attachment.

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Edited 1 time(s). Last edit at 04/17/2007 08:41PM by JoeH.

Sharp blade. Go very slow and use two hands on saw with wood clamped down. If your saber saw has a rip fence, turn it upside down and fasten in center. Screw base of saw to a narrow thin piece of wood or similar and fasten that to center of hole. If you insist on standing in the middle, keep your elbows out so you won't fall through.



Edited 1 time(s). Last edit at 04/17/2007 08:42PM by slbett.

Thanks! It's 3/4" particleboard, and and I've got arthritic hands, so it's power tool or bust for me.
The arm attachment sounds vaguely familiar-- maybe I'll do better in a search now . . .

One of my aunts husbands used a jigsaw, no attachments. Also, the hole doesn't need to be perfect, it is going to be covered by the speaker anyways. Practice by cutting smaller holes in the middle of the bigger hole. Slow and steady wins the race. ;)

Joe

Keep your eyes open while cutting helps ...

and, yeah, the hole doesn't have to be perfect, just perfect enough ...


A router attatched to a center point pivot would work, too.

I agree with billb, that the hole doesn't need to be absolutely perfect. I suggest at the very least putting a nail in the middle, tying a 7.5" string to it, and having a pencil on the end of the string to draw the perfect circle first.

-Tofer



Edited 1 time(s). Last edit at 04/17/2007 08:59PM by Tofer.

I might rent a large scroll saw or router for the day.

Tie a pencil to a string, measure 7.5 inches from the pencil tip, tack the string to the center of the slab at the 7.5 inch mark and you should be able to draw a pretty good 15-inch circle.

Drill a hole in the center, then use the scroll saw to cut it out, starting from the hole. It might take 2 blades to cut if you're a bit heavy-handed.

Alternatively, here's a good how-to for making that perfect circle with a router ('love those jigs!).
[www.diynetwork.com]

Or you could just rough it out with a jig saw or small hand saw and finish it with a dremel or some hand-filing with rounded files. I wouldn't do it with a hand saw... I know from experience that it can get very painful. But it's doable.

I hate to ask this, but can the speaker be put behind the particleboard, so all you have to do is drill out a web of air holes for the boom-chucka-boom to get out ? Sort of like swiss cheese...

Alternatively the recommendations above are good. I will also say that those little Zip-saws usually have a hole cutting attachment gizmo that works nicely for the same purpose. Basically a bar that one end is attached to the zip saw handle and the other end has a nail hole for the center of the hole.

After watching sub boxes being built buy the dozens at a friends stereo business here's my two cents -

Like the others have said - it does not need to be perfect as you are going to have the
speakers mounting flange to cover the cut . If the flange is 1/2" to 3/4" wide you can cut it
out with a $10 garage sale saber saw and a dull blade (not recommended)

What is recommended - saber saw and the proper blade for MDF - a coarse blade will cause
tear out and chipping of the line. A sharp blade will cut true and not wonder - spend a couple bucks for a blade

Use a spade bit to drill close to the line (not middle of the cut out - why cut all that extra ?

Ae you going to carpet / cover the box ? If so the over cut the line a bit more.
Nothing is worse that cutting the "perfect circle" and then fining out that you don't have room
to wrap the carpet inside the opening - add 1/4" or so (easier than trying to make the hole bigger)

When you assemble the box pre-drill all the screw holes. If you try to drive the screws
in without pre-frilling then you will probably split the MDF.

Also for a tight box use silicon at all the joints like glue to make the joints seal and
make up for not so straight cuts


edited - just to say man my spelling stinks and I really need a new keyboard !

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Edited 1 time(s). Last edit at 04/17/2007 09:42PM by lafinfil.

A router with a circle guide will allow you to cut a perfect circle, plus you can rabbit around the circle so that the speaker frame sits flush with the particle board. If you don't have a router, use a Rotozip - it should do just fine. You want the speaker to seal up the opening as best as possible. Caulk the inside joints.

If you want to try something different, build a subwoofer using sonotube. Do a google search, there are some creative designs.

All responses read and appreciated!
This box is going to ride woofer-side down on a bike trailer, so the driver will need to be mounted recessed rather than flush-- the hole won't be too visible but if I go too wide at any point I'll be pretty screwed. The foam surround is pretty beefy and will need good clearance all the way around. I'll probably mount a piece of screen of some sort between driver and opening. Had actually thought of the many small holes idea before . . . there may still be a way to do it (e.g. mount the woofer on a seperate 3/8" board to lay into the bottom of the box).
No carpeting-- the box will be painted bright yellow and have my company URL boldly on the side.
Came across a few of those tools in my search . . .
Sounds like a router with a circle guide may be in my future; the pen and string idea ought to help for now.
The silicon is a great tip!
Thanks again!

ITLX det cord in a circle? The ultimate power tool.

I might put something more substantial over it other than screen since it will be facing down and subject to all the insults of the road. I'd worry a bit too about water being kicked up by the wheels... You might be able to make a ported type box with just the port pointing down.

Can't wait to see the images of startled "boom car" drivers!

=wr=

Good call . . . could probably mount strips of wood down either side to raise the box up and give clearance for a grill. On the trailer I'm building for the box there is clearance but I want to be able to toss it on other trailers in case I need to sell "its" trailer. Would rather keep the top free of any holes . . that's where the amps will ride. I also plan to cut the top in sections secured with studs/wing nuts for easy access (may need to experiment with "gasket" material). Side wall of box is only 12" high.