My Custom 8” sub box that clears fold flat floor

[blackbetty14]

Ive been wanting to add another sub to my 18 Laramie CC with the alpine system. I’ve upgraded every speaker minus the front doors and have replaced the stock sub with a pioneer shallow sub. I’m happy with the system but I would like just a smidge more thump. I do not want to modify the truck or delete anything to get what I want. Which means not lifting the seat and not getting rid of the fold flat floor. On my 14 express CC I used a $50 box off amazon and modded it for a 12” pioneer shallow sub but I had to lift the rear seat and it had no fold flat floor.

So in keeping everything stock I have created what I think is perfect. Went to Home Depot Saturday afternoon and picked up a qt of fiberglass resin, 1 fiberglass Matt package and a 2ftx2ft 1/2” MDF board. Came home and layed down 2” blue painters tape in the driver storage area. Then layed aluminum foil and started mixing resin and putting down Matt. Of course it was 20*F out and it was flurrying lol. Gave it a few hours to harden up and pulled it out and brought it inside to cure. Then I made a template in cardboard for the MDF top, transfered and cut the MDF and sub hole. Put the glass box back in the truck and put the MDF top on and proceeded to glass in some pieces through the sub hole to join the 2 together on the inside. Gave it a couple of hours to cure alittle in the freezing weather and then pulled it out and brought it inside. Laid on more glass where they meet around the perameter and the. Let it cure for a hour or so. ( I mix heavy hardener so it cures in less than 10 min in the cup lol) after about and hour or so I went around the edge with loctite construction adhesive that’s poly and not silicone. I also applied some to the inside with my finger. Let it cure over night and this morning I wired up my 2nd pioneer shallow sub into a 4 ohm config (has dual 2ohm voice coils) and ran the wires through the end of the box that I drilled a hole for. I sealed up the hole and pulled the sub out. Now I had some black carpet left over and covered the box with that being the stock sub was black. I went through final assembly and dropped the box in. Like a glove and fits so tight I have to force and wiggle it out of its hole.

To finish it off I’m going to run 20ft of 8 gauge welding cable from the battery and ground to the seat bolts. I have a scosche LOC from my old setup I’ll use and tap into the stock sub wire for signal. For the juice I won a Ebay bid for a Alpine MRV-250 amp, mono class D puts out 250w rms at 2 ohm and 150w rms at 4ohm minimum (I get actual cert rating with the amp) but they usually will do 40w+ over the rating. The pioneer 8” shallow sub has a 600w max and 150-175w rms rating. The Alpine amp also comes with a remote bass knob which costs $30 extra so if I bought it from crutchfield it would have been $150 amp and $30 knob or $180 total. I got both for $66 shipped lol, so siked about that. I have $35-40 invested in the glass, resin and MDF. Got the sub off amazon for $60 prime. So for about $160 I have the box, sub and amp ready to rock. I have the wire, cable, carpet etc all left over from other projects.

Either way, it came out nice and it’s solid. Pics of the progress and finished product as I’m sure you all want to see. Finished sub has about 1” clearance between the top
Of the sub and the bottom of the fold flat floor.

 

[blackbetty14]

Limited to 5 pics.

Here’s some more. Fit and form looks great. Hopefully it delivers on sound.

 

[kkreit01]

Very nice job. Was this your first DIY fiberglass box? I've always wanted to try, but haven't had the guts yet.

 

[PowrRam]

That is fantastic! Thanks for posting.

 

[blackbetty14]

Very nice job. Was this your first DIY fiberglass box? I've always wanted to try, but haven't had the guts yet.

Not my first fiberglass box, but it is my first MDF top and fiberglass bottom box. Ive usually made my backing from MDF and then cut a MDF ring postioned with wood dowel and then stretch fabric, add resin and glass. This was harder as you have to guess on the height for the underside and then trim flat. Hardest part was attaching the top to the bottom through the sub opening blind.

 

[OC455]

That's AWESOME!

 

[BWL]

That's the route I should have gone. Looks awesome.

 

[Informal]

Nice work!

If I spent that much time on a box, I would have matched one of the 2 carpet colors though!

I kid!!


kinda

 

[BWL]

Nice work!

If I spent that much time on a box, I would have matched one of the 2 carpet colors though!

I kid!!


kinda

And Ram could have done the same with the plastic subwoofer box on the other side

 

[blackbetty14]

Nice work!

If I spent that much time on a box, I would have matched one of the 2 carpet colors though!

I kid!!


kinda

Haha I thought about it. But since the stock is black plastic (smooth.... not even textured) I didn't bother. Plus matching the brown would have been impossible. And since you will see these 0% of the time lol I could have just left it MDF and called it a day!

 

[blackbetty14]

Carpet is easy tho.... wouldn't take longer than 30 min to swap it out. I also have pleather or carbon fiber cloth I could have used but carpet is easier to do with the complex shape. I might keep my eye out for the ram brown carpet or I might get some grey/charcoal truck carpet just to have.

 

[kkreit01]

I think the black looks good -- as it matches the OEM black plastic enclosure.

 

[Random_Walk]

Dumb question - where are the ports located?

 

[blackbetty14]

Dumb question - where are the ports located?

What ports?

The stocker is a non ported enclosure. These subs need more space when they are ported and it just isn't possible while keeping the fold flat floor. If your referring to the speaker wire connections they are hard wired to the sub. They exit the bottom under the narrow end (underside doesn't continue all the way out to the edge) by the OEM plastic (where they butt together). The hole was silicone/sealed and the wires run around as you can see in the wire braid. I'm not sure if I will keep the wire routing that way until I have the amp installed and figure the cleanest way. Essentially I don't like the sub box connectors (spring clamps etc) as it adds another point of possible signal loss/noise. So the box is sealed and the wire running out is like 4ft which will give me enough to connect right to the amp. Removal of the sub box would require disconnecting at the amp vs at the box which will be right behind the sub box under the seat with full easy access.

 

[Spindrifter]

Awesome job! Looks great!

 

[autokraftgt]

Looks nice, you did a good job. Does the new enclosure match the internal volume of the OEM enclosure? Power match? crossover points?

 

[blackbetty14]

Looks nice, you did a good job. Does the new enclosure match the internal volume of the OEM enclosure? Power match? crossover points?

I didn't measure the internal volume but I know its pretty close to .5cuft. The Sub only requires .15-.5cuft to operate. OEM box is alittle larger as you can see in the pics but it has more recessed areas, I would assume they are pretty close to each other given the overall sizing. The OEM sub bolts to the bottom of the box from the outside and the pioneer is slightly shallower but not by much, where in the new box I have ALOT of room between the bottom of the sub and bottom of the box.

Reported output of the apline system is 150w to the sub, new amp is rated at 150wrms as well so I tried to match those up as well. I assume the stock system doesnt output as much as this new alpine D series mono amp which is probably putting out closer to 175wrms at 4 ohm. Theoretically they put out the same wattage but just at different ohm (stock is dual 2 ohm DVC) new box is the same DVC sub but wired to 4ohm load for the amp RMS.

 

[ProjectWolf]

Nice Job. Why did you bond it blind through the sub hole? Wouldn't it be easier to trim the glass down, rest the MDF down on it and glass it from the outside while the box is on a bench?

 

[blackbetty14]

Nice Job. Why did you bond it blind through the sub hole? Wouldn't it be easier to trim the glass down, rest the MDF down on it and glass it from the outside while the box is on a bench?

In order for it to line up perfectly the best way is to mount it in the car (same thing when you fab something or you build a JIG). I layed the Mat in the hole, then trimmed it flat, Layed the MDF ontop in position and then used soaked glass mat to bond the MDF to the bottom fiber glass (just like 4 peices of 2"x3", to lock the bottom and top together to be removed). Let it cure alittle till it could be removed as a unit without moving (then it wouldnt fit going back in). Then I glassed the outside on the bench like you said. I put some more in the inside after as extra bracing but most of it was on the outside. You just have to be careful when adding to the outside as it will make the peice larger (it wont fit) so you always add to the inside to make the part thicker.

 

[OC455]

What is the approximate depth you have with the box?

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