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HOW-TO build a sub enclosure for a Regular Cab Ram

2004 (3rd gen) Dodge Ram REGULAR CAB, please do not post any replies until I am finished with the How-To project. If you do however have questions please feel free to PM me with them, Thank You—Jonathan.

This will be a How-To for 2 simple sealed enclosures for 12” subwoofers in a regular cab 3rd gen Dodge Ram.

First and foremost, I am using 2 Diamond Audio D3 12” subwoofers.

The recommended air space from Diamond Audio for a single sealed enclosure is 1.5 cubic ft, these enclosures will be 1.19 cf which is a little smaller but won’t damage the drivers (woofers). I have designed the boxes to fit snugly behind the seats and still have room between them for the amp and a tray.

Dimensions for each enclosure are the same:
• Width: 15”
• Height: 22.5”
• Top depth: 6”
• Bottom depth: 11:
**Keep in mind to account for the 5/8” when measuring cuts**
I am using 5/8” MDF(medium density fiberboard), $17 from Home Depot.

Tools and supplies:
T-Square ruler

Circular Saw with fine tooth blade

Electric Nailer

Dremel with Router attachment
Wood Glue

Orbital Sander
1” framing nails
Liquid Nails

Silicone Caulk

Tape measure



The order of the pieces will determine what measurements to make. I will start by cutting the back piece in full W and H (15”X22.5”)

Next, I will have the two side pieces fit into the back and front, the top and bottom will fit inside of the two sides and the front and back.
Cut the two sides next. Since they will fit inside of the front and back you need to subtract 5/8” from both the top and bottom depth’s. 5/8”=.625”, multiplied by 2=1.25”
TD: 6”-1.25”=4.75”
BD: 11”-1.25”=9.75”
Height will not be effected so stick with 22.5”

Once you have the sides cut, you will need to make sure the front of the top piece has the correct angle to make it flush with the sides.

Measurements for the top piece will have 5/8”(.625”) subtracted from ALL sides.
W: 15”-1.25”=13.75”
Depth: 6”-1.25”=4.75”
And the front must be cut at the angle specified before. This is what it will look like it cut correctly.

The same goes for the bottom piece, .625” from all sides.
Depth: 11”-1.25=9.75”
Look familiar, these are the same measurements of depth for the two side pieces.

The front pieces gets cut last, and use the length of the two side pieces as your guide since the angle will make the length longer than 22.5”. When all fitted together it ended up being 23.25”.
Here are all of the pieces

I highly recommend assembling the pieces before securing with glue and nails to assure you don’t need to recut any piece.


I am using wood glue, however ran into a problem with a poor cut so will be using liquid nails to fill the gap.

**when using liquid nails and silicone caulk you MUST allow the product to cure before installing a subwoofer. If not, the product could damage the rubber surround.**

Apply a continuous line of wood glue to the piece to be attached.

Assemble the two pieces and secure with the framing nails

I spaced the nails out about 2” apart.

Just for safe measure I verified the two pieces with a 90degree ruler.

Alright now the same method applies to the other side piece and the top and bottom pieces.

I pushed in excess glue into areas that didn’t fit up real tight, be sure to wipe away any excess after this.

The semi-completed boxes


This portion is quite important to assure that the sealed enclosures stay sealed.
The Diamond webpage states that the diameter of the cut should be 11.1”. I am going to measure 11” to compensate for imperfections.
I have decided to make the sub 3” from the bottom of the box. I will show you the first hole completed to help explain the pics for the second cut and how to measure it.

Measure 3” from the bottom of the board and make a mark.
The center of the hole will be the center of the entire width of the board. The width is 15” so make a mark at 7.5”

Now from the 3” mark measure up 11” towards the top of the board. This will be a guide for the circle line.
In order to meet up the center of the height with the 7.5” width mark divide 11” in half and meet the 5.5” up with the 7.5”

Now you will need the compass. Spread it out to 5.5” and place it in the center that you previously measured.

This is the template you will use to cut.

I am going to free hand the dremel so I have drilled guide holes around the circle to help speed up the router. I had to make 3 separate cuts each at ¼” depth at a time to complete the cut.

Without using commercial tools, your hole may not be perfect, however a little sanding will smooth out any rough spots and the seal will still be good.

Once the glue has dried you may apply a latex based sealer caulk if you wish. Keep in mind to never use a 100% silicone caulk as this will deteriorate your sub despite curing.

Now you will need to cut the holes for the speaker terminals. I have placed them on opposing sides of the two boxes. This will allow both terminals to face inward when put in the cab.
I have opted for terminals that will accept banana posts. I don’t have pics currently of the banana posts but will post some as my project nears completion.

Measure the inside of the terminal and measure out a diagram on the box. I drilled holes in each of the corners to allow the jigsaw blade in to cut.

Once cut you may need to use a wood file or sand paper for final fitment.

While the silicone is curing, I chose to countersink the finishing nails so I can apply wood filler. This will allow you to sand the box and there should be no sign of any nails or screws.

This is where I stopped for today.

Okay, I will update with further progress. I plan on drilling holes around the sub holes to use T-Nuts for final assembly with the subs. I will sand off all wood filler and secure the front piece to the rest of the enclosure. I will sand surfaces of the enclosures and I will be having the enclosures Line-X’d instead of paint.

Again, if you have any questions, please feel free to PM me.

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Discussion Starter · #2 ·
Now that the silicone has cured I will get the front piece ready for assembly.
First I need to mark the holes where the sub will attach to the front piece.
I had intended on using tee nuts, however there is minimal room for them so I will just attach the sub with coarse thread screws.

I removed the rubber seal from around the sub to expose the holes to mark.

I raised the front piece off of the ground with plastic cups.

This allows me to place the sub into the hole and have the front piece support it.

Now mark the holes with a pencil

Front piece with marked holes

Front piece with holes drilled

Place front piece on enclosure to verify fit before glue and nails.

Solid line of liquid nails

Fit the piece on the glue then nail

Just as before, secure with the nailer and countersink the nails to apply wood filler.

Both boxes completed minus the Line-X. I will leave the speaker terminals and subs out until it is line-X’d. All that is really left to do is final sanding of the boxes and applying a bead of silicone to the front piece to ensure the seal.

Here are some pics with the boxes positioned in the truck. I have yet to decide on how I will secure them however will explain once I do.

I will end the How-To for now. The main idea is outlined and all that’s left now is the appearance and hookup. The great thing about doing this yourself is individuality. You can finish the box however you please. I will use Line-X because I don’t see that everyday.
The previous enclosures I had these subs in I also made. For that application I had primed the MDF and used Stone Creation spray paint, it turned out kinda cool too.

If you have any questions or need any other pics, let me know.

Thanks for looking, Jonathan.
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