# Audi A4 SQ Build - My first DIY project



## SuMb0dY (Oct 23, 2012)

Just thought I would share my first experiences with car audio as I start getting more serious about it. Although it is nothing new or too crazy I had some fun with the build and took plenty of photos. There are similar A4 threads on here which I used as a reference throughout the process.

The goal is SQ although I am still a beginner so I will not have the ultimate or most extreme setup for everything but I will do my best to choose great components and install them properly.

The car - 2008 Audi A4 Sedan.

I'll start with the sub-woofer - I'm going to make a FG enclosure to minimize loss of trunk space.

The trunk of the A4 (for those of you who are not familiar with it) has a door on the left side with a large plastic storage cubby in it. The cubby starts at the top with a small rack for the Bose amplifier which is sealed off from our access(for those who got the Bose stereo option on their A4) and then has a small storage space for your stuff. I don't have the Bose stereo on my A4 so for me this is just a ton of wasted space.

Here is a pic of it I found on the web. (sorry didn't take my own of this part before removing it)












After removing the plastic storage bin I found a ton of extra airspace all around where it was. I also found this extra sheet metal layer. I'll be trying to put the largest subwoofer I can in there so mounting depth is going to be the #1 constraint. If I remove this extra sheet metal I can gain another couple inches of mounting depth.










I began cutting away at it with tin snips to make some more room.










This gave me a total of about 11" of space between where the cubby door will be and the back wall. I ended up choosing the sub-woofer based on this measurement. 

I chose a JL Audio 12W6V2. This speaker has almost 8" of mounting depth which gives me hardly any space leftover for the FG buildup + the cone to have some room for its excursion to not hit the cubby door when It's played.

Now that plenty of it is cut away I can start taping up the space to prepare for fiber-glassing 



















Added a little protection for the car and smeared some turtle wax in there. This helps to remove the mold once it cures.










Laid some S2-Glass fabric in there. Taped it to stay in place this way it doesn't slide on the vertical surface its dropping into.










On goes the resin...
Just a single pretty thin layer of either S2-Glass cloth or chopped strand mat for the initial mold.










That cures and pops out without too much difficulty










Turns out the mold needed to flex a lot to come out because it reached too deep in some areas so this needed to be modified.










Don't mind the camo - I got a cheap fleece blanket for this project from WalMart for $2.50 and it happened to be camo.












I added a few more layers of FG matt and the cloth and then added strings to the weaker parts. The FG is strongest when applied to curves (and weakest when it is in large flat pieces) so one technique was to use the nylon string to give flat areas some ridges for the fabric to conform too. A stronger option was to add strips of wood but those would have added too much thickness for my purposes.










BTW - This enclosure I'm making is by no means the cheapest way to DIY. I decided to have a little fun fiber glassing with more exotic fabrics which also required Vinyl Ester resin to bond them so I would not recommend these materials for those who want the most cost effective option.

The goals for the FG enclosure to sound best...
-Minimize flex, so no acoustical energy is lost from the sub-woofer
-Have the proper internal air volume, and of course...
-Be sealed (air-tight)

To continue to build up box strength I added a couple layers of Aramid/Carbon weave fabric. 

Test fit after this cured...



















Cut away the excess










At this point it was very strong in most areas. The only areas that had some flex I was concerned with was the top outside edges. I gave these some alternating layers of FG mat and S2 fabric to make them real tough. Each side got 3 layers of mat and 3 layers of fabric.










Threw a few FG Tape strips to soak up some extra resin and help it bond nicely with the rest of the piece



















Now once that cured it was starting to get a bit thick and very strong.










To finish this part off I put 3-4 more layers of the Aramid/CarbonFiber weave fabric inside the whole piece and let that cure for a couple days.




























Now that its very strong and has virtually 0 flex I'll be able to move on to the next part which is making the speaker ring this weekend.


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## robolop (Mar 10, 2008)




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## m3gunner (Aug 6, 2008)

Sub'd...


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## Woosey (Feb 2, 2011)

Sweet! well done so far!


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## Projektmkvii (Oct 3, 2012)

well done sir


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## SuMb0dY (Oct 23, 2012)

The speaker ring will be made of MDF. I have an old router with no circle jig so I'll have to make up a circle jig for the time being. An old piece of scrap wood and some machine bolts holds the router steady enough to make a good circle.










Cut it a little too close to the edge, but this won't matter because the outside will be covered in fiberglass so this minor defect won't be seen or affect functionality.










Now that the outside diameter is cut I'll countersink a surface for the woofer to sit on.










To finish this ring, I'll make a curved bevel and cut out the center.










The first mounting ring ended up being a bit thin after countersinking a space for the speaker so I'll stack a second full piece of 3/4" MDF to it for durability.










Thick bead of wood glue should hold this together well.



















Turns out clamps ended up sliding the pieces around so those wouldn't work to let the glue set so I substituted a weight that fit the ring quite nicely. This worked perfect.










After that dried - I drilled holes added t nuts and test fit the sub.



















This worked well so I added a dab of fiberglass resin to each t nut to hold them in place and that about sums up the creation of the speaker ring. Not bad for my first time using a router


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## nellymerc (May 3, 2012)

I think those T nuts are a great idea that i didn't know existed before recently. I think I saw someone else call them hurricane nuts? Same thing? Im defiantly going to use them in my next build. Anyway great start. Sub'd


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## SuMb0dY (Oct 23, 2012)

*Placing the mount*

Now that the MDF mount is ready to go, I'll need to position it with dowels to set the final shape of the enclosure.

Found some cheap wood dowel variety packs from Walmart. $0.99 each - bought 3 packs










When I was taking the bolts out of the speaker ring so I can prepare to mount it and test fit the woofer, I just threw them on top of the W6 box... Turns out these were right above the magnet so they started standing up and dancing around. Kinda neat, but I removed them from here quickly because I don't want things messing with the speaker magnet










After many test configurations and failures, this seemed to be the final placement. I used the edges of the FG shape to make this a lot easier. Also let the hot glue dry overnight so It became strong enough to support the speaker by itself. Hardly any space behind the speaker at all.















































This piece is starting to get quite photogenic :laugh:









And has a nice custom fit











At the moment estimates have the air volume around 0.9 cubic feet of airspace with this shape. JL Spec's quote a minimum of 1.25 cu ft for this woofer but I am proceeding under the assumption that the speaker would perform better with more, perhaps around 1.5 cu ft. 

Space is really limited here so 1.5 is unlikely but I'll have to branch out and expand this piece any way I can to gain more airspace


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## SuMb0dY (Oct 23, 2012)

nellymerc said:


> I think those T nuts are a great idea that i didn't know existed before recently. I think I saw someone else call them hurricane nuts? Same thing? Im defiantly going to use them in my next build. Anyway great start. Sub'd


Thanks everyone for the encouragement =]

I wouldn't know about hurricane nuts I haven't heard that term before but yes T-Nuts are a necessity when screwing into MDF. Wood screws will easily destroy the MDF making the screw hold useless pretty quickly. I'm not necessarily a huge fan of TNuts either though. You will have to glue them down somehow like I did because when you push a screw into them, they can easily come loose and just pop out which is also pretty useless so they will need to be seated securely with some glue.


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## SuMb0dY (Oct 23, 2012)

*FG Expansion*

Before I fleece over this whole shape, I'll construct some expansion for the fleece to follow.

To find more space for the enclosure I had to renovate a little back there..

This big black plastic piece seemed to only be a holder for the small white box that had some wires going to it. I thought this was another waste of space so I moved the white box over to the right and got rid of the plastic mount all together.


















Now there's a little more room to expand.

I had plenty of leftover dowels and hot glue sticks so I started getting a little out of hand with them.




























Really cutting it close to all edges possible.



















Got a little more room up top for yet more dowels!










To make this more complicated an indent needed to be made to allow space for this wire and these protruding bolts. I will also cut these bolts down to shorten them.










It is quite ridiculous. You have my permission to laugh










Now with this new shape all set I took it outside the car and added a little more hot glue to all of the joints and let it set overnight so it gains some strength before I fleece and resin over it.










Since the sticks are not going to be structurally important I considered them just temporary until the FG took the shape on its own - So I covered them in painters tape so I could later pull them out.










Now as we all know any good stealth install requires the key element of stealth, Camo!

Used some spray adhesive to make sure the fleece took to the contours properly and test fitted the new shape.


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## mklett33 (Dec 7, 2009)

Looks like a suspension bridge! Progress is coming along, keep at it. I think you could have gotten away with a more simple skeleton, but this is just a different way of coming to similar results. Good luck with the build. 

How much air space are you going for btw?


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## SuMb0dY (Oct 23, 2012)

mklett33 said:


> Looks like a suspension bridge! Progress is coming along, keep at it. I think you could have gotten away with a more simple skeleton, but this is just a different way of coming to similar results. Good luck with the build.
> 
> How much air space are you going for btw?


Thanks =]

The suspension bridge went up pretty quickly and easily with hot glue so I didn't bother trying to think of another way to make the skeleton at the moment since I had fun getting carried away with the dowels.

Progress is slow - the resin is taking basically overnight to cure in each session I do because it's really cold in the garage right now. I started doing the layup in the garage and then bringing the piece into the basement to cure where its a little warmer but my family is not enjoying the FG smell at all. It gets in the house pretty easily.

I haven't tested this woofer yet so I'm not sure what air volume I'll like best. I'm assuming the bigger the better for now with the space constraints I have. I would like to hit 1.5 cu ft and see how that sounds. I'll most likely modify the finished product by adding poly-fill if it comes up short on volume, or if by any chance it has too much volume I can decrease the size the woofer sees with some expanding foam or something like that. I doubt it will wind up being too big but I'll cross that bridge when the time comes.


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## SuMb0dY (Oct 23, 2012)

*FG Expansion*

After many adjustments over the past couple days I finalized a shape


Resin on the fleece



















Test Fit failed so I needed to trim the fleece a bit. Some of the openings also gave me easy access to pull the dowels out











The fits is good now











Took advantage of the fleece openings to improve the connection with the MDF ring. Gave it a few layers of FG weaves which overlapped quite a bit onto the fleece for an excellent bond.










Finished adjusting most of the shape with S2 Glass and then gave a few layers of the Aramid/Carbon weave over the whole fleece to start adding strength










Trimmed around the ring and prepared one final expansion.

Cardboard and painters tape set this up real quick. 










Glassed and tested fit










With this final shape being a success I will now just have to add more layers of kevlar/carbon fiber fabric until I am satisfied with the enclosure's strength and then add the wires/terminals


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## Woosey (Feb 2, 2011)

Great work!

You could use those bolts also for mounting your enclosure perhaps..


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## SuMb0dY (Oct 23, 2012)

What do you guys think, should I carpet the enclosure or leave a carbon/aramid finish?

Originally my plan was to carpet the enclosure in black and wind up with something just like GrandMarkie's enclosure. 

GrandMarkie's Enclosure... http://www.diymobileaudio.com/forum/1332271-post115.html

After seeing how nice the weave looks I'm starting to think it might be sacrilege to cover that up...


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## robolop (Mar 10, 2008)

SuMb0dY said:


> What do you guys think, should I carpet the enclosure or leave a carbon/aramid finish?
> 
> Originally my plan was to carpet the enclosure in black and wind up with something just like GrandMarkie's enclosure.
> 
> ...




Carbon dude, what a stupid question.

GO 4 IT


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## SuMb0dY (Oct 23, 2012)

robolop said:


> Carbon dude, what a stupid question.
> 
> GO 4 IT


Haha thought so

I'll start surface prep for the finish tonight. Looks like lots of sanding and bondo are in my near future


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## boom_squid_2 (Jan 29, 2008)

That carbon is wicked cool.


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## robolop (Mar 10, 2008)

SuMb0dY said:


> Haha thought so
> 
> I'll start surface prep for the finish tonight. Looks like lots of sanding and bondo are in my near future




Carpet has everyone already, carbon, I do not think so..











So you know what you should do..


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## robolop (Mar 10, 2008)

boom_squid_2 said:


> That carbon is wicked cool.



That is CARBONKEVLAR dude


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## SuMb0dY (Oct 23, 2012)

robolop said:


> That is CARBONKEVLAR dude


Yup, CarbonKevlar..... Cause nothin' says bulletproof install quite like a Kevlar Subwoofer box


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## robolop (Mar 10, 2008)

SuMb0dY said:


> Yup, CarbonKevlar..... Cause nothin' says bulletproof install quite like a Kevlar Subwoofer box



Pretty **** to work with


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## SuMb0dY (Oct 23, 2012)

Awesome! I am trying fiber glassing for the first time with this project so I don't have all the tools or tricks down quite yet but the laminating finish on that piece is excellent!

Robolop that isn't your current ICE ICE POLO project is it?


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## SuMb0dY (Oct 23, 2012)

The Carbon/Kevlar box is ready for use. On an unrelated note I also slapped on some winter tires and their lookin pretty cool too 

Blizzak WS70's on Anthracite painted 16" Rims
For the bad snowy days










Shined the new tires up and took em for a ride















































Okay back to the subwoofer enclosure..

Estimated volume with packing peanuts. Had a convenient 12"x12"x14" box too.










Looks to be just about 1.25 cu feet. I'm going to add polyfill anyway and maybe in the future experiment without it










Surface prep for the final layer of carbonKevlar

Plenty of bondo around the ring and sanded for days. The goal is to give a nice big curved bevel with the carbonKevlar and have it meet right at the flat surface of the ring, and then paint the ring black










Sub fits with the bevel adjustments









Since I don't want the carbonKevlar to get on the ring I'll tape it off before I start




























While working to wet this layer out I eventually cut away most of the inside circle so it was easier to stretch this to bond to all the curves.

Into the drying room... which is basically a tiny bathroom + a fairly big space heater. This resin was not curing in the cold garage so I had to do this for pretty much all the drying sessions














































Used a dremel and a cutting wheel to cut out the ring









Bondo and sanded again so the ring appears to meet the carbonKevlar seamlessly.

Covered it in painters tape and plastic so I can spraypaint


















Gave it a few layers of black









While I was at it I also sprayed the W6 trim ring yellow just for fun. That's John Deere Yellow haha



















Time for some speaker terminals...

Drilled holes and filled them with DAP silicone sealant. Pressed the terminals through the wet sealant and it spread out and sealed itself pretty nicely. The stuff is white but dries clear.










Prepared the internal wire. Crimped some ring terminals on these. Gave them heat shrink just to color code them.









Woofer accepts bare wire so that's what it will get at that end








That's Kicker 12Gauge wire

This gets sandwiched between two bolts for a good connection. The first bolt also holds down the binding post while the sealant dries.










Here's a few pics of the finished product. It's ready for the speaker and to be placed into the car. I will have to install the amp before I can hear it but I am expecting good results! 

The 12W6V3 also just came out, will be able to order it from JL or their dealers in a few days. Future plans to upgrade to a V3 and sell the V2 are viable because the mounting depth should be the same


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## SuMb0dY (Oct 23, 2012)

Looks really cool until you find out the hard way that carbon fiber is electrically conductive... :banghead:

Gunna have to pop out the binding posts and thoroughly surround them with electrical insulation to get rid of the short the carbonfiber is giving me


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## mkeets (Oct 6, 2011)

The fabric reminds me of these:








Usher 8137A 8" Kevlar/Carbon Fiber Woofer 296-616

BTW nice box!


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## SuMb0dY (Oct 23, 2012)

mkeets said:


> BTW nice box!


Thanks!!

That woofer looks really sick. It would be a nice touch to this box haha


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## 98koukile (Nov 3, 2008)

The only thing I might have suggested was something like body filler or resin filler (whatever they call it) to smooth out before the final layer to make it more presentable but definitely an awesome job for diy, I love the ingenuity.


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## SuMb0dY (Oct 23, 2012)

98koukile said:


> The only thing I might have suggested was something like body filler or resin filler (whatever they call it) to smooth out before the final layer to make it more presentable but definitely an awesome job for diy, I love the ingenuity.


Thanks!! 

I thought about using more body filler but space was very limited and the piece was getting difficult to fit into it's location in the car. 

Also, once this is installed, most of it will be concealed unfortunately. The only part that will be able to be seen is just an inch or two around the speaker so this is where the body filler went.

Here is a brief update on the progress for now...

I needed to remove the binding posts so I can add electrical insulation to them









These holes will be drilled slightly wider to allow room for the binding posts + Insulation

Binding Posts simply get heatshrink. I stacked 3 layers of it to enhance durability.










These fit into the slightly larger holes, and excess heat shrink is carefully trimmed away with a hobby knife.










Inside the enclosure, the heatshrink will meet a rubber washer to insulate the nut as well.










Color coded heat shrink makes this look appropriate, and by nature of the rubber used this is air-tight so no silicone sealant was used here.












To seal the woofer against the enclosure I'll enhance its gasket. Stock gasket removed. It was a bit thin so I added a fatter one.











This stuff was perfect - fat, airtight and squishy makes it ideal for a variety of purposes. I also added some of this between my license plate and my trunk which stopped rattles there. It is a much cheaper option than buying a 'license plate kit' from dynamat or other deadener brands and worked perfect to seal the woofer and kill license plate rattles.

















Insert speaker...









The W6's Dual Voice Coils are wired down to two ohms according to the instruction manual - and this is how I know I am doing it right 









The air seal in the box is very close to perfect which wasn't easy to achieve.
One of these days now I'll finally be able to hear it


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## SuMb0dY (Oct 23, 2012)

*Deploying the Subwoofer!*

After making more revisions, the new subwoofer is finally in action!












I decided heatshrink wasn't the best option to protect against shorts so I went a different, more durable/safer route

I cut a decent sized hole in the box, and replaced this with a block of wood instead. Binding posts will pass through the wood now. 


Air sealed the wood block with some bondo on the inside of the enclosure, and bonded it on the outside surface with more resin.
Sorry not too many pics of this step as I was in a hurry....










Looks like a decent gap for the wood block but its filled in with bondo + resin


Mocked up a wooden "L" block to secure the enclosure to the car body. This will keep the box pushed down into its place so it doesnt budge with hard braking or turning.

















It screws into the car chassis and sits up here by the binding posts, in their new wooden home.










Box gets wired up and tested for success!! Now the trunk gets put back together and you see the final result.













































Just enough room for it back there without causing any problems




















A little more of the Carbon/Kevlar is visible through the vents









The sound is great so far!

You might have noticed I have an amp rack set up already. I'll gladly share how that was made and it's components when I have more time to organize pictures and post here. =]

Enjoy the long weekend for those of you celebrating MLK day :laugh:


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## robolop (Mar 10, 2008)

I assume you are going to put a grill for speaker?


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## SuMb0dY (Oct 23, 2012)

robolop said:


> I assume you are going to put a grill for speaker?


For now, the door will stay because Im taking a heapload of crap with me for a roadtrip this weekend so the speaker will need protection.

I am thinking of a plan to remove the door and protect the speaker with maybe JL audios W6 grill. Im wondering how to make it look nice and not appear as if the door is missing. 

Maybe a trim around the door or something, any suggetions?


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## fast4door (Aug 2, 2012)

well done you surprised me!


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## SuMb0dY (Oct 23, 2012)

fast4door said:


> well done you surprised me!


Thanks!!


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## gtwibell (Jul 11, 2015)

Oldish thread I know but nothing ventured...

Seriously impressive sub enclosure build. Want to do something similar with my B5 RS4. A question - how do you get to the back of the rearlight cluster to swap out bulbs?


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