Build a Box Workshop

[linet90]

I finally found the time to get started on my sub install. I wanted to build this thread to show some of the DIY members how to construct a fiberglass enclosure.
Currently I am still in the process of building the enclosure as time and arrival of material plus a 4hr drive back to my home town hold me up (needed a garage).

Hardware:
-two 5mm bolts / length can vary, at worst buy longer and cut shorter
-four 5mm washers
-two 5mm crush washers or loctite
-two 5mm nuts
-aluminum sleeve / cut to needed length

To get started I first decided on a location to the left in the trunk where the factory amp in mounted (as some of the members have already done). Now we have to relocate the amp, I moved it above the wheel well.

This required the drilling of two 5mm holes into the cars sheet metal.





The way the amp is mounted one side of it is suspended so I got a longer bolt and a sleeve for it (sorry for the blurry picture).


This is the first step I took, I have more done and I will be posting as time goes on. I am open for any questions or suggestions members might have.

NOTE: Some of the tactics I used to build the box might not be the most efficient ones but do work and are completely air tight sealed. I have not built tons of these boxes but enough to know what I am doing, I have been in the business of automotive installations for the past 4 years and recently moved onto a different career.

Hope You Enjoy It

[linet90]

Here are the next steps:

Now a mold has to be made, well there are many ways to accomplish it. I decided to make a MDF base since their are screws sticking up from where the factory amp bracket was mounted. It makes it a perfectly flat surface and much easier to work with.

So now that we have that, I needed to make a mold. I tried to find modeling foam but none of my local stores had any so I made one out of cardboard.



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Now once you test fit it to the trunk and make sure it will fit and the trunk will close (make it a little longer up front so you can cut back later) you want to use some painters tape and tape the inside of the mold.



Then grab some tin foil and lay that over the tape (it acts as a release agent).



Ok, test it one more time in the trunk and you are ready to lay down you first layer of fiberglass.
-Make you mixture of resin and hardener (I recommend using a cheap brush and soda can).
-First put one layer of just resin down - let it dry until its tacky
-Then put fiberglass down- cut it into smaller pieces to make it easier to work with
-Apply some resin onto the fiberglass - let it sink in - and then apply more where needed
-By letting it sit for a little also helps push the bubbles out easier - you should see no white fibers

Once complete with the first layer wait until it is dry and has hardened.

Repeat these steps for each layer you will put on.

After two layers you can pull off the mold and fiberglass the back of the box (you should have 3 layers total)







The rest of the layers can now be applied I recommend a total of 6-8 layers. Once I was done I had 8 layers just to make it extra strong.

Note: As you apply layers you have to watch out for air pockets. Most of the time you can see them, the big ones mostly show up as white spots. You can either pushing them out with you brush or use a fiberglass roller. The roller works great and it a good tool for a beginner plus it makes the job that much quicker.

[linet90]

Hmm I guess no interest on this subject?

[bigred875]

I just noticed this thread and have a great interest, thanks for posting. I have dabbled in fiberglass before but not very successfully. My cousin and I plan to have a go at building one for the spare tire well in his G8 and if all goes well my wife's forester followed by my A8. Please keep posting.

[quality_sound]

Two quick things.

1) Tear fiberglass mat instead of cutting it. It'll make it FAR easier to work with. If you're using fiberglass cloth obviously you HAVE to cut.
2) You need to make sure that your fiberglass is COMPLETELY saturated. Putting on "enough to sink in" is wrong. If you lay down your resin and you can still see the fiberglass, you need more resin. When 100% saturated fiberglass mat becomes see-through. That's when you know you're good. From your pics it looks lier you've gotten good saturation, but your description may lead beginners to use too little resin.

I really like your mold process. It's not how I do it but it looks simple and for noobs, simple is best.

[bigred875]

Two quick things.

1) Test fiberglass mat instead of cutting it. It'll make it FAR easier to work with. If you're using fiberglass cloth obviously you HAVE to cut.
2) You need to make sure that your fiberglass is COMPLETELY saturated. Putting on "enough to sink in" is wrong. If you lay down your resin and you can still see the fiberglass, you need more resin. When 100% saturated fiberglass mat becomes see-through. That's when you know you're good. From your pics it looks lier you've gotten good saturation, but your description may lead beginners to use too little resin.

I really like your mold process. It's not how I do it but it looks simple and for noobs, simple is best.

how do you do it?

[linet90]

Two quick things.

1) Test fiberglass mat instead of cutting it. It'll make it FAR easier to work with. If you're using fiberglass cloth obviously you HAVE to cut.
2) You need to make sure that your fiberglass is COMPLETELY saturated. Putting on "enough to sink in" is wrong. If you lay down your resin and you can still see the fiberglass, you need more resin. When 100% saturated fiberglass mat becomes see-through. That's when you know you're good. From your pics it looks lier you've gotten good saturation, but your description may lead beginners to use too little resin.

I really like your mold process. It's not how I do it but it looks simple and for noobs, simple is best.

Thanks for the advise, I will reword it. looking at it again I should of said, spread some resin onto the fiberglass - let it sink in - and then apply more where needed - by letting it sit for a little also helps push the bubbles out easier - you should see no white fiber. Yes the fiberglass should be completely saturated as quality_sound stated. I often but a lot of resin on which isn't bad but it does make the box heavier.

Also what do you mean by "test fiberglass mat" ?

[quality_sound]

That was supposed to be "tear" not test. lol. I'll edit it.

[linet90]

That was supposed to be "tear" not test. lol. I'll edit it.

Oh ok, I have seem it done that way, I just prefer to cut it. It keeps the fibers packed and wont create knots but its just two different ways of doing it.

[quality_sound]

how do you do it?

I pretty much eliminate the mold process altogether. I'll tape off the area I want to glass and work in the car. I also don't use foil as a release agent. I use either mold release or some manner of wax since that's all mold release is anyway. Any paste wax will work. Hell, PAM will work in a pinch. Once I get the back mold done I pull it out of the car, add as much strengthening as necessary, position my sub mounting ring, stretch fleece over that and the edge of the mold, and resin the fleece. The fleece will add a SUBSTANTIAL amount of material and save a buttload of time. Then it's just finishing the enclosure.

[quality_sound]

Oh ok, I have seem it done that way, I just prefer to cut it. It keeps the fibers packed and wont create knots but its just two different ways of doing it.

I recommend tearing because it lets the mat go into corners better without lifting and it lets the edges of pieces next to each other blend better. That's it.

[linet90]

^ I have done that on cars that have pockets in the trunk like a civic. In this case everything was just sheet metal. One other benefit of not doing it in the car, you wont have to deal with the smell of resin in the car after your done.

Although the way quality_sound does it is the way most shops do. Its easier sometimes and faster, their are many ways to get the job done.

[quality_sound]

^^^Exactly. It's all about the specific application. TBH, as a beginner's guide yours is a better way to go. I NEVER recommend beginner's use resin in their cars. Not only because of the smell but also because they tend to get resin all over the place and once it sets, that shit doesn't come out.

With this guide will you be doing a full MDF face or a ring and pull? Recessed?

[linet90]

^^ It takes a lot more masking off when building inside the car. I take a clear painters tarp and throw it over the trunk and just tape it down to around my working area this way nothing will get touched. As for the front I will be posting that in my next steps. It will be a MDF ring and a fleece pull over.

[quality_sound]

I tried the plastic drop cloth but I can never get it to sit down correctly so I tape my glassing area and then use the drop cloth everywhere else. It takes longer and uses a LOT more tape though.

You doing a double ring so the sub is recessed?

[hender]

good for you linet, can't wait to see the end result!

[bigred875]

I pretty much eliminate the mold process altogether. I'll tape off the area I want to glass and work in the car. I also don't use foil as a release agent. I use either mold release or some manner of wax since that's all mold release is anyway. Any paste wax will work. Hell, PAM will work in a pinch. Once I get the back mold done I pull it out of the car, add as much strengthening as necessary, position my sub mounting ring, stretch fleece over that and the edge of the mold, and resin the fleece. The fleece will add a SUBSTANTIAL amount of material and save a buttload of time. Then it's just finishing the enclosure.

thanks, this thread i starting to collect some good info

[malish]

Any updates? Curious to see what the final product looks like. Def want to do this on my car.

[linet90]

Any updates? Curious to see what the final product looks like. Def want to do this on my car.

I am heading back to my home town this weekend so I will have updates either over the weekend or Monday.

[linet90]

Ok, sorry for the late response but here is what needs to get done next.

The mounting rings need to be made.
You can either sink the sub in (which requires two rings), or make one and let it stick out. I did both, first I started with one ring and was not happy with the clearance between the speaker and the door in the trunk. After ripping the face off 3 time and sanding everything down I make two rings. The specs for the ring OD and ID can be found on the tech sheet that comes with every sub.
After the rings are cut out trim any extra material so it can be level with the rings and surfaces of the box.




If anyone wants to see the pictures of one ring I will post them on request.

Now grab some fabric or a T-shirt like I did and it has to be stretched over the face of the box tight. To keep it in place I predrilled holes and and used flat head nails. I really couldn't figure out any better way to do this so if someone knows better please share.




Cut off any extra material hanging and apply resin first, let it dry , apply fiberglass. I went to the extreme and added another 7 layers to the front I think its a little to much but that's just me.







Their it is.
The next step would be cutting the circle out and sanding the box as flat as possible, adding bondo to any needed areas and in my case applying the vinyl.

You can also paint or carpet it.

[Dasquade]

Very nice job on the enclosure and thanks for the info. Will help me a lot in the future.
Please post some pics of the final box and the sub specs you will be using. Same for the amp and wiring please.

[linet90]

Thanks, I am going back to finish it up next weekend so I will post pictures then. Although I can't figure out a good amp location anyone have suggestions?

[cory_can]

Looks good....coming along well.

[linet90]

Here is the finish result of the box and it sounds amazing!

After cutting out the sub hole you have to bondo any uneven surfaces. Then I decided to vinyl wrap the box. It was my first time using vinyl with these kinds of curves so it didn't come out as good as I wanted it to be but its ok.








Now drill a hole just enough for the speaker wire to come through and silicon the hole. I tied a knot in the line just in case the box was ever to move and pull the wire out.



On the same side of where the hole was drilled I mounted connection terminals, to make it easy if you would ever want to remove the box.



As for mounting the box I cut another platform and used the factory screws that held the amp bracket as mounting points. I made the holes a little small so it can be press fit on.



Velcro the bottom of the box to the platform. I used a little to much I cant get the box out of the car now.



Now mount the sub into the box and your done!

[linet90]

Onto the amp wiring.

I mounted the amp under the rear deck lid. Couldn't find any other place and I looked everywhere.
All my wiring is wrapped in VW/Audi tape to give it the factory look.

First I got my line level signal. In my case I tapped RCA cable right to the factory sub since the JL amp has a build in converter.



Ran the wires on the right side of the trunk and down to the battery.



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Here's where they came through. You can get them through the rear deck lid so they are not shown. My hands were small enough to fit under, the only challenge you will have is trying to get the wires under the trunk arm resting point foam. Its hard to describe.



Then I ran the amp control and remote to the center consul. Made a switch for the remote wired to the cig lighter.



All that's left is mounting the amp.

[quality_sound]

Looks great!

[linet90]

Thank You

[bigred875]

well done, thanks for posting

[jbradle7]

Thanks to Linet90 for the inspiration! I used his great write-up, but took a slightly different path in making my box.

I'm installing a JBL MS-8 sound processor; I wanted the processor/amp tucked away out of sight and since the drivers-side has the factory amp and harness, this seemed like a good place to mount it. I relocated the factory amp (same as OP) and used the factory amp mount with a few small modifications, to mount the MS-8 processor and a Massive Audio N2 sub amp. I decided to use the passenger-side cubby for the location of my subwoofer enclosure.
http://www.audizine.com/forum/showth...=1#post7137509

The cubby volume was not nearly large enough for a 10" sub, so I started off modifying it to fit my needs.

[linet90]

Glad I could help. The sub box looks awesome great idea! I like how you used the factory cuby to form the box. Looking forward to see how this all unfolds.

Question: how are you keeping the box in place?

[!38 T]

This thread rules. JBradle7, your setup is exactly what I wanted to do.. but my cars a lease at this point, and in the sake of clean removal, i'm going to add some padding around the outside of the compartment, then mold the whole thing. I checked the PN for the cubby hole on genuineaudiparts its about $120.. worth the extra time on my end to be able to swap it in again if need be.. do you have a rough idea of how much volume you have in yours? my sub requires 0.66 ft3, which I can definitely manage in that spot, just wondering what yours is for scale if you measured..

edit: just spent a while crawling around my trunk and answered my own questions. thanks OP!

[jbradle7]

.. do you have a rough idea of how much volume you have in yours? my sub requires 0.66 ft3, which I can definitely manage in that spot, just wondering what yours is for scale if you measured..

I did the foam peanuts trick to measure and it is right around 0.6 ft3. My speaker calls for 0.65... I'll add some polyfill to slow the waves down a bit.

The box is finished and painted now and I have all my mounting brackets fabricated. Next step is to remove the rear parcel shelf and orig sub and add sound dampening to as much of the trunk as possible before wiring everything. Will post picture update once complete.

[!38 T]

very interested in seeing the end result. if you tap the stock sub line.. can you still plug in the stock sub and have the signal being sent to the new amp as well?

[Smeghead]

Any more finished projects? Just picked up my sub to start down this road.

[jbradle7]

Question: how are you keeping the box in place?

The large bracket goes over the fuse box and attaches to 5mm threaded studs in the floor. The small bracket attaches to a section of the inner quarter panel through an existing unused hole. Since I don't have access to any fancy metal working tools or good materials, I've used basic framing brackets available at your local hardware store (modified, as required) for the lower support and a small corner brace for the upper support. Both brackets are pretty sturdy so they should work fine to secure the box using some 1/4-20 bolts, well-nuts, and a couple fender washers.





Sound dampening



I've removed the factory sub to allow more bass to enter the cabin. I simply de-soldered the internal leads and left the baffle in place to support the rear parcel shelf. After removing the sub, I re-installed the factory grill for a neater appearance.

[linet90]

Awesome, How did you remove the rear deck lid, did the seats have to come out?

[Bezlar]

Very nice!! This is going to be my winter project. Thanks for the detailed write up.

[jbradle7]

Awesome, How did you remove the rear deck lid, did the seats have to come out?

The C-pillars pop out, then carefully remove the speaker grills ( I cracked one of mine but it's not noticeable at all) exposing 4 screws in the top of the baffle and then one other on the passenger side. There are 4 clips that need to be disengaged on the forward edge nearest the seat backs. No need to remove seats, just folded them down... assuming you have folding seats, although I hear this is an option now.

This link is very helpful:
http://forums.audiworld.com/showthread.php?t=2790664

[linet90]

Thank you that will help me in the future.

[jbradle7]

Here's the finished product: