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Chas
12-04-2004, 10:34 AM
Here is something I have stumbled on to that gives professional results.

My latest project is to change out my woofers from a pair of Altec 414Z woofers per channel, for some 2231 with 2235 cones, two each a side as well. Aha! I thought I finally had a use for the new spin saw....no such luck, the circle cutting jig only allows up to 12" diameter holes.

The prospect of using a jigsaw guided by hand was not too inviting, my experience at getting a hole with a decent shape has not been great.

I looked around and found that Lee Valley Tools had the perfect solution for C$31.50. It can make holes from 6 to 40" in diameter. It's a plastic universal cutting router jig that allows you to exactly drill a pivot point for a 13-31/32" diameter hole. You simply remove the base of your router, (oh yeah - Sears had plunging routers on sale for C$99.00), and screw the jig to the router.

The jig comes with a 1/8" post that goes through the pivot hole you make in the jig and into a 1/8" hole in the center of your cut-out.

Presto, perfect holes in about a minute through 3/4" MDF. I can't believe just how easy it was to cut four woofer holes.

www.leevalley.com (http://www.leevalley.com)

P/N 46J91.01

Ken Pachkowsky
12-04-2004, 04:56 PM
Thanks for the post Chas. That is one slick jig!

As stated above. These are the gems that this site is great for!
I always hate cutting holes for diy projects.

Ken

majick47
12-04-2004, 10:41 PM
Ken I'll be cutting holes in the baffleboard of my L200b speakers for 2405 tweeters tomorrow morning. Will be useing a portable drill with a 3 1/8 hole saw blade, plan on useing two small pieces of 1/2" ply bolted to each side of the baffleboard to keep it from splintering. Not much room to work with either, 1 1/2" inches from the top of the baffleboard and about the same distance from the LE85 horn cutout. Crossing my fingers and wish me luck.

Ken Pachkowsky
12-04-2004, 10:45 PM
Have done the exact thing your doing with 4320's..

I used a Disston 3 1/8 hole saw. It worked perfect. I used masking tape on the baffle to prevent splinters and that worked great as well.

Ken

boputnam
12-04-2004, 10:54 PM
Nuthin' finer... :coolness:

Jasper Circle Jig (http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=365-260)

You can Search the Forum on that string, to find some specific tips.

majick47
12-05-2004, 12:07 AM
The ply might be a little overkill compared to masking tape but I figure it can't do any harm and I have to drill the four (4) mounting holes anyways. I'll let you know how good/bad it turns out. Sorry to say I don't have the room to fit the Jasper jig onto the baffleboard that's already mounted in the L200b cabinets.

Steve Schell
12-05-2004, 09:42 AM
My partner Rich and I needed to cut several 23" diameter holes in 3/4" baltic birch recently for a horn subwoofer project. Rich came up with a great method which requires only a plunge router and a suitable piece of scrap plywood. The scrap needs to be about 4" wide and four or five inches longer than the hole diameter. Holes are drilled in one end for the router mounting screws and for the bit to pass through, and a pivot hole spaced at a distance equal to the desired hole radius from the far edge of the bit. Then a pivot hole is drilled in the workpiece, and that bit can then be used as the pivot, as it fits tightly in both jig and workpiece. The jig is put in position and the plunge made to begin the cut. The jig is then rotated about the pivot until the hole is completed. The nice thing is that the jig overlaps the cut on the opposite side (unlike the expensivo jigs) which aids greatly in stability toward the end of the cut. It is also best to support the center waste section from underneath as the cut is finished, so it doesn't fall and damage the end of the cut. Remember to think **safety**, as we're dealing with a router here.

Actually one jig would serve to cut many different sized holes; one would just need to drill a pivot hole in the right location for each size.

johnaec
12-05-2004, 10:00 AM
Horn subwoofer!!! 'That pic?? More info!
:jawdrop:
John

Chas
12-05-2004, 11:01 AM
Holy crap Steve! What a picture. Your plywod jig idea is identical to the Lee valley concept. Geez, I coulda saved 30 bucks or so.....:biting:

Guido
12-05-2004, 11:16 AM
STEVE, what are you doing there ?

boputnam
12-05-2004, 12:15 PM
Sorry to say I don't have the room to fit the Jasper jig onto the baffleboard that's already mounted in the L200b cabinets. Got it. So that this Thread is a bit more obvious for the Search function, here's a Adjustable Wheel and Circle Cutter (http://www.leevalley.com/wood/page.asp?page=32275&category=1,180,42316&abspage=1&ccurrency=2&SID=) Link, and pic...

Now, Steve Schell, you have got to give us some details!! :shock:

Chas
12-05-2004, 12:42 PM
Quote: "Got it. So that this Thread is a bit more obvious for the Search function, here's a Adjustable Wheel and Circle Cutter (http://www.leevalley.com/wood/page.asp?page=32275&category=1,180,42316&abspage=1&ccurrency=2&SID=) Link, and pic..."

Bo, I tried one of these for my 2405 holes and snapped the bit as soon as the drill moved slightly off perpindicular. It works great on a drill press, though.

Alex Lancaster
12-05-2004, 02:04 PM
:) Chas: As You found out, You should never use a "flying bit" cutter freehand, a holesaw is good; Sears use to have these bit cutters, pretty HD, their new stuff is flimsy, so having a good machinist, I had one made of 4140 CrMo, tempered it, and on a good drill press or milling machine, I have cut 1/4" plate steel, slowly.

boputnam
12-05-2004, 02:16 PM
Oh, so you were talking about the Universal Circle Jig (http://www.leevalley.com/wood/page.asp?page=40968&category=1,43000,43001&ccurrency=2&SID=). That's what I first thought, but wasn't sure if that was any easier to work on a recessed baffle...

majick47
12-05-2004, 03:18 PM
The 2405 tweeter holes came out 100% perfect with "0" slintering. With the help of my brother, who actually did most of the work and has quite a bit of woodworking experience, the holes look like they were done at the factory. Used the 2405 tweeter mounting plate as a template and bolted it to the face of the baffleboard with a 1/2" piece of ply on the back of the baffleboard. The four mounting bolts held everything tightly in place. We didn't use the hole saw guide bit and placed the 3 1/8" hole blade into the hole of the 2405 mounting plate and drilled thru the baffleboard with no problems. I checked the cut we made against the factory cut for the LE85 horns and ours was smoother. Later I'll paint the tweeter and bolt holes with semigloss black paint and install the 2405 tweeters. I was sweating this one but with all your helpful suggestions the project was a complete sucess. A big THANKS to all of you!

Steve Schell
12-05-2004, 03:49 PM
Hi guys,

The subwoofer in the picture was built to take to the Rocky Mountain Audio Fest in Denver this past September. It is a slightly domesticated version of my original Big Bottom sub, using the same 15 Hz. flare rate and folding scheme. I named it the Big Ed in honor of my brother Ed Schell who did the final design work and created cutting plans.

The BB sub was designed to exhaust out the side and be placed along a wall, aimed at a corner four feet away. I had figured out that the expansion out of a floor to ceiling 90 degree corner would actually come close to continuing the 15Hz. flare expansion with good accuracy out to a total path length of 35' or so. The internal folding scheme was a variation of Dr. Olson's W bin, as used in the Shearer Horn System.

With Big Ed, we changed the design by rotating it 90 degrees so that it exhausts at the floor. Several wedge shaped waste areas inside were eliminated, resulting in the tapered shape. From the beltline down, it slowly flares out in front. This was done to provide stability and to to allow for enough back chamber volume and flare cross section near the mouth. Although in theory this design does not offer quite the room loading of the original, in practice it works out much better when placed in the center of the rear wall. In my case this means that guests now have to enter my living room from the entryway through a tapered slit... surely a minor annoyance when good sound is involved.

If anyone wants more details and drawings on my sub designs, please drop me a line at [email protected]. I have a letter and bunch of attachments on the subject to send out.

P.S. Big Ed is not really 15 feet tall- it is 7'6". Rich took the picture from the ground to lend that impression.