Bfowler's Big Bad Box Building Butorial, er, I mean Tutorial

[Bfowler]

Avoid Alliteration Always

Materials used:

-lots of 1.25" corse drywall screws
-pro-bond wood glue
-4' x 4' sheet of 3/4 birch plywood (many use MDF, but low Weight is VERY important in this application)
-t-nuts for mounting the sub
-bolts that complement the t-nuts
-parts express bolt style terminals

tools used:
-18v cordless skill saw
-18v cordless drill/driver
-framers triangle
router with 1/4 straight bit
4' level
tape measure
pencil (mechanical gives you a consistent line)





pic 1:

The First key to Success is to have a plan, even a crappy one (as shown) firstly I jotted down my given variables. These are values that I can not change. In this case I was limited to a 14" max height and a 28" width.

I also measured the slope of the back of my back seats. It was approximately 4" greater at the bottom near the floor then the top near the “ceiling”. I will refer to this number (4”) as my “D2” (or the difference of my bottom depth vs. my top depth) (this will make more sense if you reference http://www.bcae1.com/spboxnew2.htm and make use of their volume calculator)

This left me with my “D1“ (top depth) as my adjustable variable. I could make this length smaller or larger to hit my target airspace. I chose 5" in this case because since my length value was so long ( ) I wanted to make the box as small as I could and still have clearance for the woofer. Using all these numbers I calculated some basic geometry and found my interior angle of ~17.5 degrees. (The slope of the box face)

I also knew that the thickness of the wood was 3/4” keeping this in mind I had "Lowe's" cut my entire board in half upon purchasing it to 26.5 inches wide. (We will later find out that they can't cut that straight, but close enough that I could correct it with sanding)

Plans:
Length: 26.5 + .75 +.75 (for each end piece) will give me my magic width of 28”
Height: 13.25 =.75 (I planned to screw the front baffle flat to the bottom piece of the box, and to face of the top piece so I didn’t need to ad 1.5 inches, just account for the bottom)

Using the above linked calculator I will end up with a total value (before bracing) of 1.34
A good middle ground between the pg recommended .85spl and 1.65sq recommendations for my xenon 10d2 woofer.

Cutting time:

The piece if wood pictured is the piece I had “Lowes” cut (like a Home Depot if you don’t have them where you live)

It has a uniform width of 26.5” per my cutting request (more or less….grrr, they aren’t the best cutters)

This will stream line the process because now I only have to make 1 cut for each of the four pieces the will form the non-end pieces of my box.

Pro’s have table saws…..I don’t. I have a cordless skill saw so I will have to make do.

To ensure a straight cut I take a measure of the length of the piece I am about to cut and make a cute arrow (pic 2) I do this on both the far left and right of the board to make sure its straight. Then using my handy level I draw the line I am about to cut. (pic 3)

The saw I use has a 1” guard on it so I add 1” to my measured line, and secure my level down with clamps creating a cutting fence. This will keep my cutting line true.

From my previous calculations I move my angle setting on my saw to 17.5degrees. I do this first because the piece I cut will produce an identical angle on the end of the left over board. If you plan it properly, this will reduce the number of total cuts you will have to make. (pic 4) I will repeat this process until I have a top, (angled 17.5 on one end) front baffle (angled on both sides, complementary) back, (straight on both ends), and a bottom (also angled 17.5 on one end – you will notice later that it is 3 inches longer then the previous specified depth of the box, this is because I will use that 3 inches to create a buffer pace between the back of the seat, and the woofer cone. It will also give me space for my one-day custom grill)

[Bfowler]

Now that we (or me as it were) have Four 26.5” x X” pieces, I will start joining them. First get wood glue. Apply liberally (pic 5). I stand the 2 pieces up on my bench (which for me is the spare plywood on top of saw-horses) to make sure that the side is flush. Once you are satisfied with the fit, Clamp the other piece you are joining and pre drill your first hole. Then drive a screw in. (pic 6) now that you have your first screw established, you can pre drill more, I only pre-drill 2 at a time to A: make sure that they all line up and don’t move as I tighten down the board, and B: allow my bit to cool down between holes. Results may very for you, but this is what has worked for me. Not very quick, but it’s accurate.

After I joined the back, top and bottom (since the front is angled on both edges I save it for last) I decided it was high time for some bracing. Some left over scraps worked good for this, I cut them to fit snuggly between 3 of the sides and glued and screwed in place (pics 8 ) front (pic 7) screw placement from back,

[Bfowler]

Now I have the back, top, and bottom joined, and stabilize with braces, so I will prepare my front baffle.

Breaking out my tape measure again I find the middle of the face (and take into account that both sides are complementary sloped)

From this point you can use a compass to draw a circle and cut it out, but I happen to have a circle jig that bolts to my router, and it whoops ass. (pic 9) It has measured holes (the jig is face down in the picture, so you cant see the numbers) so all you have to do is pre drill a hole in the center of your front baffle, and drop a pin (nail) through the correct hole measurement, and start cutting. The only fault of this process is that the router and guide are secured to the piece you are cutting out…..which means as you finish your circle, the guide will be free to move, and that is bad. To solve this I secure the circle with clamps when I have only a couple inches left so that I can finish the circle with no movement of the guide. (pic 10) .

After you are done cutting you are left with a hopefully perfect hole for your sub. Now is a good time to test fit it. (pic 11)

I took the rubber gasket off of my xenon sub, and I fit perfect, almost no movement, and it wasn’t sitting on top of the hole either. Next I rotated the sub to be straight and used a sharpie to mark the holes. (pic 12) I drilled out the traced holes and fitted the t-nuts into them. To tighten them all the way, I used the largest washer I could find that fit onto the bolt. I then used my cordless drill to tighten the bolt into the t-nut until the spikes were set, and then removed the bolt.

[Bfowler]

Now it is time to attach the front baffle, but first I want to brace it. You can see from pics 13 and 14 how I used some left over scrap that was already cut to the complementary angles and recessed the width of one sheet of plywood so that I would match up when I fastened it down. I attached the braces with glue and screws coming from the front side. (you can see the screws slightly protruding from the back) (pic 15) (You can also see that I took that picture before I installed the t nuts :p) pic 16 shows a side view of the front baffle secured on and the bracing lining up with the existing pieces

[Bfowler]

To create the end pieces I placed the box end up onto my reaming wood and used it as a stencil. Theoretically I should have been able to just draw the end piece and cut it out based on measurements, but by using the stencil method I can correct and potential errors that might have slipped by me. Because I had been attaching the pieces all along end up, the right side was perfectly flush. The left side however reviled that the lowes cut was not straight and I had to sand 2 corners down to get the end to sit flush before attaching.pic 17

the terminals i bought from Parts express, and are pretty cool, they are a straight bolt that goes all the way though, so you don't effect the structural integrity of the box. just drill a hole and screw the terminal throughpics 18 & 19

[Bfowler]

done

[stipud]

So uhh... just noticed you don't use MDF. That looks like plywood... wtf? Is this some Brian secret for ultimate SQ?

[Bfowler]

it is Birch plywood, not quite as "continuous" (it has some small gaps in the grain) as MDF, but about 1/2 the wight which is the most important factor for me. it was about 2x as expensive as MDF also

[Bfowler]

i can't really tell a difference in sound but it is easier to work with, it saws and drills much easier, the screws seem to hold better, and is noticeably lighter.

it might be hard build a box and stain it as the edge's that get cut splinter up quite a bit so the corners would look a little jagged. if you used wood filler or something to smooth them out, and then painted, it would probably work.

unless cost is a big deal, i don't think i will ever go back to MDF.

[VW337]

Birch ply = lighter, more rigid (less flex) than MDF. However MDF is far more accurate to work with and can be machined to far more accurate tolerances.


If you plan to stain the birch all you have to do is use a high speed fine tooth blade/saw combo for less splintering and cut it at a 45 degree angle or even use a joining router bit.

[AVICJR]

What size tee nuts did you use? I was looking at the 10-32 5/16. The screws are just regular machine screws? I will be using them to mount a Ti Elite 12d.

[Bfowler]

i used 10-32 on this one, but for a sub like the ti elite, you should go as big as you can. be sure to factor in that if they are too big the might hang over the lip when the sub mounts

[Bfowler]

DONE! If anyone has any thoughts, criticism, comments, suggestions additions. just let me know

[Francious70]

Umm... no pics

[Bfowler]

goddammit, not again

thank you for your constructive criticism, your post is important to us, and we will be assisting you shortly. All of our technicians are currently assisting other customers. please do not refresh and repost as your post will be handled in the order i which of was received. Your expected wait time is....64.....hours....and.....14....minutes.....please stay on this thread and thank your for reading this tutorial.


(on hold muzzak)
buhdump duhnuh duntdunt duh doot
buhdump duhnuh duntdunt duh doot
buhdump duhnuh duntdunt duh doot baduh ding.....

[stipud]

fixed.

[Bfowler]

thanks. way to beat that estimated wait time.

why did it do that? how does it reference the addresses for those pictures?

[stipud]

You can set permissions for each forum. For some reason the attachment mod sets itself up so that only moderators may upload and download attachments by default. I have to set it for all registered users...

Anyways, I went through ALL of the forum permissions now so there should be no more problems.

[CTKNY]

Bfow

whats the extra wood for on the box. (front of the sub)

[Bfowler]

that was to

1: space it from the back of my seats
2: ....this is going to be difficult to describe....so it can act as a lip so I can stretch fabric from it to create a flush interior piece.


so i have fold down seats in my car, and the box fires forward. i am going to create a faux interior that stretches from the sides of my fold down seats to those "extra" edges. i will try and make a picture. give me a couple days.

it will make a lot more sense then

[CTKNY]

I have a Chinese swing in my bedroom...

[Bfowler]

I have a Chinese swing in my bedroom...

i see. i dont know what that has to do with my box, but thats awesome!

[CTKNY]

that was to


this is going to be difficult to describe.... i will try and make a picture. give me a couple days.

it will make a lot more sense then

[Bfowler]

that was to


this is going to be difficult to describe.... i will try and make a picture. give me a couple days.

it will make a lot more sense then

ok here are recent pics.

A is the before and B is the planed after. the "added" black area shows how i will stretch fabric and fiberglass to create panels covered in vinyl. so when you drop the seats there will be a flush recess to the subs. it makes sense in my head. i promise when it happens i will post pics

[dako]

Just wanted to say thanks to bfowler for the t-nut idea. For some dumb reason, I never thought of using those little suckers in my previous installs. I used them last night to mount 2 RSDc 12"s and they worked like a charm. So nice to be able to set the clutch on the cordless drill without fear of a wood screw stripping out the MDF. But that's never happened to anyone, right?