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How To Build A Downfiring Subbox


paulguy

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Well I'm building a box for another forum member, so I'd thought I'd take some pics and do a how-to.

 

Supplies needed;

  • A sheet of 3/4 MDF.
  • Wood glue.
  • Staples or Brad Nails.
  • Carpet. I use metra # AC364.
  • Spray adhesive I use V&S 185.
  • Speakers(need them to test fit).
  • Flat Black paint.
  • Speaker wire(should use 12 gauge).
  • Speaker termainal cup if you want one.
  • Or hot glue.
  • Sandpaper.
  • Screws for speakers.

Tools Needed;

  • Table saw.
  • Router or jigsaw.
  • Drill.
  • Brad nailer or stapler.
  • Sander. I use a dual action 6".
  • Tape measure.
  • Hole saw.
  • Pencil.
  • Knife.

To start of build a frame under the seat. I like to keep my boxes a couple inches back from the front of the seat, I like to line the front up with the gap in the sill panel and I use that for reference to make sure everything is square.This one is 14" x 57". About 8.5" high in the front and 7" in the rear. Minus the 3/4 top too don't forget.

Don't nail it together yet.

2011-08-27114826.jpg

 

The angle on the front and back is about 8 degrees. This is how I find the angle. Crude but I get paid by the job so it's all about the speed.

2011-08-27135343.jpg

2011-08-27135404.jpg

 

Then I run the front and back through the table saw and cut 2 inches off. With a 3/4" bottom, it's only 1 1/4" to the bottom, but the floor dips down farther under the seat. Now I glue and nail the frame together.

2011-08-27131723.jpg

 

A little sanding and trimming to get it just right. I'm really picky. Still more to go.

2011-08-27131709.jpg

2011-08-27114524.jpg

 

Now to build the top and bottom. We have to build the hard part first, these are just 14" x whichever length to get to the hump. Remember each side is a different length.

Cutting the holes for speakers should be done first. Don't put them too close to the sides if you have big subs. I'll show why later. If you don't have a template you can use a pencil stuck in a piece of wood screwed into the center of the speaker to draw a circle to cut the hole with a jigsaw.

2011-08-27143741.jpg

 

Glue and nail the bottoms on and then its on to the hump...yeah compound angles...fun. But once there finished, then the box is almost done.

2011-08-27144921.jpg

 

Subs fit, but they're tight. If you sub is deep then this one(about 5"), no problem, just cut out holes in the top piece for the magnets to go through and cover with wood or fibreglass to seal the magnet up. I don't have any pics of doing that, but if anyone wants to know how, just ask.

SAM_1289.jpg

This is alot of room for a deeper sub, probably up to 7 or 8" deep, like I said earlier, don't put them too close to the edge of the box so that the magnets will not hit the bar under the seat.

SAM_1320.jpg

Glue and nail the top on. Done building and on to finishing

SAM_1297.jpgThis one's getting a logo, guess what it is...

Cut out holes for terminal cups now before carpet.

Edited by paulguy (see edit history)
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Lots a few different ways to do seams in carpet, but they require some skill. I prefer no seams, but it takes some work and maybe a little practice.

Start by sanding down all the top edges and sides. I use a 40 grit disc on a d/a

SAM_1292.jpg

SAM_1295.jpg

If i was to guess, I probably go to around a 3/4" to 1" radius on the corners.

Blow it off and test fit. I had to do a little notching on this box right at the back corners because it's so wide.

On to carpet.

Lay you carpet down(remember there is an inside and outside to the material), put the box upside on the carpet, check to make sure you have enough material to wrap all the sides.

Tilt the box back on it's side and spray glue the box and the carpet.(always do both sides). Let it tach up for a minute.

tilt the box forward and the carpet is glued onto the top.

Spray glue one end with glue on the box and carpet.

SAM_1301.jpg

Start on the corners and pull on each corner out and the carpet will stretch.

Lift up the carpet while pulling up and mate the corner. Go to the next adjacent corner and do the same.

SAM_1303.jpg

And keep going till the corners are on.

The go in between the corners and pull the material and work out the wrinkles.

 

SAM_1307.jpg

SAM_1310.jpg

Once the carpet is adhered to the sides and the wrinkles out, you can glue the underside and smooth out any wrinkles on the bottom. I go a couple inches from the edge.

SAM_1312.jpg

I trim the carpet and inch or so from the edge.

SAM_1313.jpg

Just keep going till it's all trimmed up. If you have an stapler handy, you can staple the edges to make sure it can't peel back.

SAM_1314.jpg

Cut out the material where your terminals are and install them now.(I always soldier my wires to the inside of the cups before i put them in. makes life easier.

 

Done. I just have to finish the logo and I'll upload some more pics when that's done. But other then that, screw the subs in and stuff it under the seat and your good to go.

SAM_1315.jpg

Edited by paulguy (see edit history)
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  • 1 month later...

Wow that looks great man! That's going to look ( . )( . ) i can swing by tomorrow if you'd like and we could take some pics for these guys. I just finished carpeting and mounting everything. I've been breaking the box I'n well during my commutes, near clipping volumes for hours and it's doing awesome. :pepsicheer:

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