M-21 Giveaway Build Pics

[gmichael]

corock wrote:

I've got the outside cut on half the boards. It takes about 15 minutes to cut each board, plus prep, get the tunes going etc., so I get a few boards done each night after work. I really don't have much wood working experience so just figuring out how I was going to do this took quite a bit of research and trial and error. I planned on doing all the cutting by router and trashed the first board finding out that it was the wrong tool for the job. Jigsaw was the right way to go. I'm also experimenting with how I'm going to finish the wood once its together.

Once all the outside is cut, then I have to cut the inside, glue it together, put in the bracing, cut out the hole and sand it. The sanding is going to take quite a while. So I'll probably put up some pics once I've got it to the point where its ready for sanding.

What trouble(s) did you have with the router? That's what I am planning on using as well. I have a jigsaw also, but I thought that the router would give me a more persission cut.

[corock]

I thought the same thing. Because I am cutting so many boards I created a template and used a guide on the router to follow the template. I had to do the entire template free hand because my entire design is curves (I went with a subtler version of design 2, less curve on the back of the box). Because a router can move in any direction quickly, my lines aren't exact, there are little ripples here and there. Those transfer to the actual boards as I follow the template. Those aren't the end of the world since they can be sanded out. Here's where the real trouble started. When your using a bushing guide to follow a template you cant actually see the bit of the router, its not open like a regular router base plate. So you have to follow the template strictly by feel. While cutting the first board the guide slipped above the template and I put a 1/8" dent in the board. I can't sand that out and filling it would hide the grain, which I might want to keep when I finish the project. And routering 3/4 plywood is a very slow process. The jigsaw can't go sideways without intentionally turning it and I don't need a smooth cut on my project because lots of sanding is already mandatory.

[gmichael]

OK. I see now. Sounds like a lot of work. My design will have me just cutting a bunch of circles. No template. How is it going with the jigsaw now? Making more progress?

[corock]

Yes, now that I've got it down its going pretty good. The orbital jigsaws they build now days (I haven't used one in 20 years) cut really fast. However, every board is a different pattern from the last. The basic shape of the box is a standard pattern that I trace from a template, but the cone part of the box requires a different dimension on every board. That requires a lot of measuring, thus 15 minutes to cut one board even when I'm most efficient. And I'm not rushing, any error outside 1/16" trashes the board. I think so far I have two boards that I might have to replace because of errors while cutting the rounded corner at the back of the box.

[sub_junkie]

Its going to be interesting to see how the finished box ends up. Its looks like a difficult design to do, along with any small errors can throw the whole thing off. Glad to see that you've made some progress I would be anxious to get the box built if I had one of the 21" drivers When I got my Mal-X, my Uncle and I built the box in ~8 hours? That included getting everything ready, getting the materials, and other stuff.

[sub_crazy]

Hey Corock,

It might be good to show some pics along the way or ask for help from the members here if you ever get stuck. There are a lot of members here who have already gone through what you are doing and may have useful tips.

[corock]

You bet Mike, I won't hesitate to ask for help. I've gotten lots of advice here and know how much wealth of knowledge and experience this forum has to offer. You're right, it might be good to show some pics along the way in case somebody has some suggestions or spots something I don't see.

[corock]

Okay, here's where I'm at so far.

My first step was to find a curve that suited the size of the box. I created it on sketchup, but because its asymetrical it posed the problem of replicating it in real life. So I made zoomed in photocopies of the sketchup and pieced them together to give me a blueprint to work off.




This is the template I made for the router, which didn't work. But it gives you and idea of what each board will look like once I have the outside and inside cut. Of course this template doesn't include the modifications I make to most of the boards to creat the cone part of the box.



this is my first cut that I use as my sketching template for each board that follows. It gives you a visual of what the top of the box will end up like.



Creating the cone requires gradually changing the dimensions of the above template. This diagram is how I determined what measurements to use.



As you see here I'm about half way through the stack of plywood for the outside cuts. The cone part of the box is starting to take shape. So is the daunting task of getting that rough circle down to a smooth surface.



This side view gives you a glimpse at how the cone will blend into the box once its all sanded down.



And this is the 64000 btu electric furnace I just bought for my garage because the 16000 btu construction heater I've been using just isn't cutting it.



That's it for now. I'll get some more pics up once I've got all the boards cut and can show what the full box will look like.

Here's something I could use help with. I plan on making the front of the box about 2.5" thick so I can counter sink the sub in 7/8" and have 1.5" to mount it to. Any idea on how I'm going to cut a circle through 2.5" of solid wood?

[gmichael]

Nice start. It's bigger than I imagined. It will be interesting to see how the ends of the plywood sand down. What type of plywood are you using? How will you sand?

[corock]

i'm using pre-sanded 3/4" plywood from Home Depot. My plan is to bring down the large areas around the cone with a wood rasp, then for the entire box I have a belt sander, random orbital sander and hand block waiting. I was thinking I'll have to take it right from 100 grit to 600.

It is pretty big, but once I've got the driver in imagine there is only going to be a 3" wood frame around it.