New sub box build coming

[bigred90gt]

So, I upgraded the OeM alpine sub to a Kicker Comp 8” shallow mount and installed a Kicker Key 500.1 to run it. While it is miles better than the OEM sub, this is my first ever 8” sub (and first junk box as the OEM is), and it’s just not enough. I’ve decided to build my first fiberglass box and install a Kicker L7T 10” solobaric sub under the drivers back seat. This will free up the larger passenger side storage area and I can keep the larger passenger side fold flat floor. I intend to keep the seat at the same height, so I need to figure out a way to keep the box profile as low as I can.

ive build tons of boxes, but I’ve never worked with fiberglass. I know resins quite well, and have used all kind of epoxies at home and work, so I’m not too fussed about that. The biggest concern I have is mating the fiberglass to the MDF I’m going to use for the top. I’ve seen a few builds, but no one really addresses that part. Also, where the edge of the box will be toward the center, the under seat compartment is kind of a valley right there. Any tips on how to close that gap would be helpful. Basically looking for any general tips that can help. I know to tape the ever living **** out of everything. Some people say to put foil down, some people say it isn’t necessary. I’m not worried about aesthetics on the bottom, as it won’t be seen. I’m going to make a ring of 1/2” MDF to attach to the fiberglass, and a solid 1/2” MDF board for the top where the sub will sit. I’ve thought about another MDF sheet to “countersink” the sub, but I’m not sold on that being necessary.

any help would be great. Thanks in advance.

 

[misfit77]

Styrene resin sticks to mdf well, but provide a strong mechanical bond to the mdf first.

In previous projects i make the shell first. Then the I staple glass cloth to the mdf to build a transition between the two. More staples the merrier. Then apply resin and adding chopped fiber if possible.

I linked some photos of a tire speaker box for my jeep. I ended up creating a fillet of resin and chopped fiber on the inside. Then fender liner on inside for dampening.

https://photos.app.goo.gl/LJFE44vWe5ELMDch8

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[canadiankodiak700]

Yes resin bond to MDF is extremely strong. Usually all you need is to lay resin soaked fiberglass against the MDF and when it cures, the bond will really hold it. As you may the glass for the sides, you can lay some pieces of rope/string soaked in resin on your second layer and then a layer of glass over that. Creating a small ridge Inn the wall of the box. Once cured, this will really strengthen the box and help prevent flex as the sub compresses the air in the box.

Prep wise, last down a couple layers of tape, foil is definitely a good idea too as it pulls away easy. But the key is a really good layer of wax. Paste wax works really well. Buff on a good layer all over the tape or foil before you start laying the fg and resin. This will really help with release.

Any odd dips, valleys, or bumps, tape them up, wax, and lay your ft. They will add strength just like the rope/string I mentioned before.

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[PincheOso]

Please post pictures. I've been thinking about doing the same thing with a 10" or possibly a 12" L7T. I want to keep my folding floor so would like to build something flush.

 

[bigred90gt]

Please post pictures. I've been thinking about doing the same thing with a 10" or possibly a 12" L7T. I want to keep my folding floor so would like to build something flush.

that is the post I found that I want to model it after. Except I dont want 3 layers like they have. I plan on just the first trim ring, then the top of the box.

 

[bigred90gt]

I’m finally buying stuff and getting ready to start. Ordered the sub and wire terminal over the weekend, picked up some fiberglass resin/hardner and mat today, along with 3/4” birch plywood (not the expensive Baltic birch, but for a small box and single 10”, I’m certain it will be fine), some wood glue and some screws to finish the box. Got some black carpet coming as well, and already have the spray adhesive.

Took the fold flat floor out today and double checked the template I made (outside corners will be rounded, just didn’t want to mess with cutting that into the template). Looks good to go to my eye. Probably won’t be till next weekend before I can get to it, since my wife is off work this coming weekend.

can anyone tell me what the plug under the back seat is for? It has what looks like a cap on it but it goes to nothing. There’s one on each side. It doesn’t look like it would be looped in the cap, so I’m sure it is just protection for the connector, but I’m curious what it is for in trims where it is used.

 

[fprevos]

That is for underseat lighting.

 

[bigred90gt]

That is for underseat lighting.

So I assume no problems if I just cut it? I’ll never put lights under my seat.

 

[fprevos]

So I assume no problems if I just cut it? I’ll never put lights under my seat.

If you cut it with the doors open it will short and blow the fuse. They are hot when the doors are open. You could cut them one at a time and protect the ends.

 

[bigred90gt]

If you cut it with the doors open it will short and blow the fuse. They are hot when the doors are open. You could cut them one at a time and protect the ends.

Gotcha. Thanks for the info.

 

[bigred90gt]

I got the base ring cut out and the sub mounting square cut. Before buying the wood, I measured the clearance to the bottom of the seat and it looked like it would be fine with 1.5” thick leaving plenty of clearance. Once I got them cut, it was a little closer to the cloth on the bottom of the seat than I wanted. I don’t want to come hitting the cloth, even though it’s just loose cloth and not any kind of structure. Instead of trying to match cut a thinner piece for a new base ring, I just recessed the cutout for the sub. I cut a square 1/4” deep into the plywood then chipped out 3 layers to recess the sub. Since it’s 3/4” plywood, it still leaves 1/2” for the mounting surface. I’ll paint the recess black, and trim the carpet to the edge of the recess when I put it on. Given the x-max is only 9.2mm, it should allow enough room that it isn’t hitting the cloth. I’ll finish cleaning up the opening tonight and cut the hole for the speaker terminal to mount. Next step will be fiberglassing the Shell, but that has to wait until next week when my wife is back at work unfortunately.


This picture just shows the cutout relative to the base ring. I need to figure out the best place to mount the speaker terminal. I’m thinking to the left where that gap between the sub cutout and base ring is, but I don’t particularly want it at the front of the box where the wire will be prominently visible with the seat up. Unfortunately, there just isn’t a ton of room for it otherwise.

 

[Cableman]

I made one for my 08 ram on the passenger side, i removed it and plan to install it soon in my 16.
I used ¾" mdf as the top ring then once i laid 5 layers of fiberglass i attached a top layer of ¾" mdf.
The 1sts layer i used fiberglass cloth. I sprayed the under layment which was tape and aluminum with 3m adhesive spray, this keeps the cloth in place while i fit it nice and flat. Then i just loaded it with resin.
Each layer after was just cut, wet and applied. I went with cloth/mat/cloth/mat/mat as the layers.
Came out great. Still have to carpet it.

 

[bigred90gt]

Nice! I’m hoping my fiberglass job looks half as good as that. I have never worked with fiberglass, so this will be my maiden voyage.

 

[bigred90gt]

I made one for my 08 ram on the passenger side, i removed it and plan to install it soon in my 16.
I used ¾" mdf as the top ring then once i laid 5 layers of fiberglass i attached a top layer of ¾" mdf.
The 1sts layer i used fiberglass cloth. I sprayed the under layment which was tape and aluminum with 3m adhesive spray, this keeps the cloth in place while i fit it nice and flat. Then i just loaded it with resin.
Each layer after was just cut, wet and applied. I went with cloth/mat/cloth/mat/mat as the layers.
Came out great. Still have to carpet it.

Where does your wiring go into the box? That is my only hangup so far. I'm considering putting it on the vertical flat section between the driver and passenger side, but that would require me custom making a little wood plate to go there and not glassing over it. Or I could glass over it, and just cut a hole through the wood and glass, but I would need to get a thinner piece of wood for that (no need for 3/4" thick there). I'm trying to keep the look as clean as I can, even though the seat will be folded down over it 99% of the time.

 

[Cableman]

Where does your wiring go into the box? That is my only hangup so far. I'm considering putting it on the vertical flat section between the driver and passenger side, but that would require me custom making a little wood plate to go there and not glassing over it. Or I could glass over it, and just cut a hole through the wood and glass, but I would need to get a thinner piece of wood for that (no need for 3/4" thick there). I'm trying to keep the look as clean as I can, even though the seat will be folded down over it 99% of the time.

Thanks It was my 1st fg job also!

I just drilled a hole for wire to go through in that outside back corner, soldered an xt60 connector used for RC lipo batteries on the end. Plug the hole with silicone or what ever.

 

[misfit77]

I did the same drill hole in a hidden location. Seal with silicone.

 

[bigred90gt]

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Apparently, one key piece of information that Kicker fails to put into their owners manual (or I failed to see it when I read the online version) is that when you are cutting out the square, you have to radius the corners significantly. They give you the radius of the outside of the sub, but not the cutout that I could find. Just gives a 9-5/16” dim for the cutout. So I cut a 9-5/16” square. The sub came in last night, and all of the effort I put in to remove 1/4” thickness to recess the sub and get ready to build the box was for nothing. When I dropped the sub in, the radius did not cover the corners of the cutout. So I basically had to get a new sheet of wood and start over. Fun times.

 

[bigred90gt]

Kind of glad it didn’t work out honestly. I got a new sheet of birch ply and got a new ring and top cut. This time, I used 1/2” instead to provide some extra clearance. The surface area is so small I’m not worried about flex. I used to template from the sub box to make the cutout. Probably be Thursday before I can start on the fiberglass, though I might just wait till the weekend just to give myself more time.

 

[bigred90gt]

Today was fiberglass day. I’m hoping this last layer will stiffen it up enough I can call it done. There’s 4-5 layers already. I used more mat than I figured I would. After the first go (2 layers in most places), it was still so flexible I decided to add another layer or 2 before I took it out of the truck.

Tomorrow is trim the matting and finish the box day. Plan is to have it finished and installed tomorrow at some point. We shall see going to get some caulk (to make sure there’s no air leak paths between the layers are), run a bead along with a thin bead of wood glue, and stick some screws in it to hold it together. Carpet is here, so once the glue/caulk dries tomorrow, I’ll be finishing it up.

 

[bigred90gt]

Well, here she is. Came out pretty good for my first time ever using fiberglass I think. It’s solid as hell. Sounds much better than the 8” shallow mount kicker I had in the OEM box for sure, though now I think I need a new amp. And if I get a new amp, it will drown out everything else, so I’ll eventually need to amp the doors and dash. I’m afraid I’ve started down the proverbial rabbit hole again. Last time I did this, I ended up with a couple grand into the system. I told myself when I bought this truck I was going to leave it alone. Silly me, lol.

I ran a small bead of silicone right where the fiberglass meets the wood on the base and a small bead of wood glue at about the halfway point on the base ring before I put the top layer on and screwed them together. Should be air tight.

The carpet looks grey in the picture, but that is just the lighting. It’s black and matches well with the carpet in the truck.






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