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Old 26-04-2009, 07:55 PM   #1
robm
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Thumbs up HOW TO: Custom Fibreglass Subwoofer Box for a Mazda 323 Astina

How To:

How To:
- This is just a simple guide to building a custom fibreglass subwoofer box for inside a Mazda 323 Astina hatch, but can realistically be used for any car. I personally researched how make a fibreglass box from many sites, but the best ones were:
- http://chris.pfharlock.com/glass/index.htm - This site explains in detail how to create a fibreglass box specifically for the Astina. The problem I found with this was the final finish he got on the box.
- http://www.rexnet.com.au/forum/lofiv...hp/t71937.html - Not specifically for the Astina, but still explains the process really good.
Remember to do your research before jumping into it.

Materials needed:
- Fibreglass mesh/netting
- Fibreglass resin (around 4L or less)
- Fibreglass resin hardener
- Wood glue
- Brushes (el-cheapo ones will do)
- Mixing sticks (I used metal rulers)
- MDF wood – (3/4” inch for the base and the rest can be ½” inch or less)
- Masking tape
- Aluminium foil
- Containers for mixing fibreglass
- Fabric for stretching over (cotton and fleece ones work good, anything that can stretch greatly)
- Velcro strips
- Resin for carpet
- Terminal cup for the back of the box
It would roughly cost around $120 for materials

Tools needed:
- Electric jigsaw
- Drill with 1/8 bit
- Measuring tape
- Electric sander (this one is not to important)
- Rubber gloves and breathing mask
- Scissors
- Staple gun
- Nail gun

1 – Building the wooden outer shell of the box
For the outer shell of the box, many people use just a wood base, or even completely fibreglass the whole thing. This is just personal preference, but I choose to use wood for majority of the outer shell of the box. This is mainly because it provides more strength, is easy to cut, and when using wood for the top of the box, you won’t have the hassle of fibreglass dripping down and not sticking properly.
Firstly create a base for the box using the wood. Remember, this piece of wood will have some influence on the final shape of the box. I found that the best way to do this was to use the carpet of the Astina boot as a template. Using your jigsaw or cutting tool, cut the base and test fit it, it should fit in pretty close to the plastic moulds in the boot.



Next, cut small pieces of wood for the whole back of the box. A good way to do this is to cut a template of the shape needed out of cardboard. As you are going along use a nail gun and wood glue to stick the pieces of wood together. Each time, test fit it and make sure it follows the back of the plastic mould. I ended up using some braces just to hold it in the right position; these braces are just temporary and can be taken off later when the fibreglass holds it in place.



Step 2 – Fibre glassing the outer shell of the box
First of all you must protect your car like there was no tomorrow . Use a thin and clear plastic sheeting to cover the paint on the bumper, the seats and the carpet. For the section that needs to be fibre glassed use masking tape, make sure there are no gaps.

Next, use aluminium foil and wrap it around the plastic mould and floor, sticking it on with masking tape.



Use several layers of foil until you are confident that it will not leak through. Put your wood structure right up against the foil – this will push it back a little into the right shape.




Ok, once that is done its time to fibreglass. Firstly put your wood structure on top of the foil and if needed use a heavy weight to pin it right up against the plastic mould of the car. Pour your fibreglass resin into a container along with a tiny bit of hardener (only a couple of mL’s, not too sure of the exact amount). Remember not to mix too much as this stuff goes off fast and will very quickly become unusable. Get the fibreglass netting and place it on the foil. With a brush with resin, dab at it until the netting stays on by itself and then brush fibreglass resin all over it. Keep doing this until you covered the whole area with a mixture of the netting and resin. You should make sure that you actually fibreglass more area that is needed, that way you can cut a neat line later. It is very important that you make a strong connection between the fibreglass and the wood. Once finished, wait for it to dry, this may take an hour or longer and then add another layer by doing the exact same thing. After this, it is best to let it dry for many hours or preferably over night.



Step 3 – Removing and Trimming
In this bit, just simply pull out the fibreglass mould and be gentle with it so the fibreglass does not snap. You can expect the mould to come out with many layers of foil attached to it – try to remove as much of it as possible. Now put it back into your car and you will be happy to see it fits in nicely and tight. Now use a marker and draw the line you want it to come up to –this will determine the final back shape of your box so be careful – and also remember not to go for too much of a tight fit as you still need to carpet it. Use an electric hacksaw, grinder, or any other cutting tool to cut your line. After this test fit it, and re-trim if needed.




Step 4 – Strengthening the box
Put another layer of fibreglass on the box, concentrating on increasing the strength. Make sure you get all the patchy areas and also the joints – such as the joints between the wood and the fibreglass, and even in between the joints of wood – mainly to make it stronger and air tight.

Step 5 – Making the Sub Ring
Your sub should have came with a template, if so, now is the time to use it. You should firstly draw the inner line of the circle onto wood. Now cut it, I just used an electric jigsaw and it seemed accurate enough. For the outer bit try and go more rather than less – this way it’s less likely of snapping.



Now put your sub into it and make sure it fits. After this cut pieces of wood to mount the ring onto the box. This step is important as the angle of the ring will determine your final shape of the sub, you can use a jigsaw to cut the basic shape of the pieces and then sand them to get the right angle. When mounting the ring make sure your nail/screw into the wood bit of the box and not the fibreglass. Now test fit it again, if you like the angle move onto the next step.



Step 6 – Fibre glassing the front
Get a material which can stretch a lot, I used an old cotton sheet, although its said that fleece is more suitable as it soaks resin well and dries with less crinkles (thanks to 70NYD for that one). Stretch it very tight over the box and use a staple gun to pin it on the back of the box.



Put a layer of just plane fibreglass resin for the first layer, use no mesh. Fibreglass everywhere on the front except for the middle of the ring, even go past the edges a little bit. The resin will go through the material and soak it, after an hour or longer it should be dry. The material may have slight ripples when dry, but don’t worry; the carpet should hide most of this.



Cut the material which is covering the hole for the sub ring. Now using both mesh and resin fibreglass the inside of the box. Don’t worry about the general area of the box; just mainly concentrate on the corners, especially the joint between the material and the rest of the box. Cut the excess material that you no longer need so that there is a straight and neat line.



Now fibre glass the outside of the box, getting everywhere on the front of the material. Once dried and if needed, apply another layer of fibreglass on the outside to make it stronger. Now test that it fits, and for the first time it should actually look like a sub box. There may be large gaps, but most of those gaps will go by carpeting so don't worry too much.



Step 7 – Finishing and carpeting
Pre drill holes for your sub to screw in to and make sure your sub sits tight.
I sprayed the outside of my box with a coat of GMH black, just for looks if I ever needed to take the box out. It also helps if the carpet is slightly see-through so you won’t see the material under.
The carpet you use must be very flexible – if it doesn’t flex enough it won’t properly fit the outside of the mould. Now get your resin for the carpet (I don’t remember what it was called but you can easily get it from Bunnings) and brush it onto the outside of the box. Then wrap the carpet around the mould – but make sure there are no air bubbles. Once this is done and the resin is dried, cut the excess carpet – keep some past the edges for more tightness when the box sits inside the car.



Test fit it and make sure it fits, hopefully it does and goes right on the edge you want it to. Ok, now a good idea is to put a strip of Velcro between the box and the car – you don’t want your sub to roll out as your driving!



And now you're done, enjoy your sub!!!Here are some final pics of mine:





ADDITIONAL INFO
Fibreglass safety – Remember to always wear a breathing mask, gloves, and long clothing – fibreglass sticks everywhere and the netting is so itchy you will be feeling it for the next week or so.

Let your sub box out of your car when you’re not working on it – the smell it leaves in your car is very...interesting.

When fibre glassing, cut the fibre glass netting into strips – don’t just put it on in one big go or else it will be very weak.

You can put on the terminal cup at basically any stage – simply pre drill a hole and screw the cup in when the box is finished – but put it on the wood part of the box and not the fibreglass bit.

Before starting, find out the max and min volumes for your sub, the manufacturer of the sub should have this on their site. Then calculate the volume that you estimate your box to be and make sure it is suitable. My box is around 40L or a little bit more.

Can you move the box? It can be easily moved out of the car in under two minutes to get access to the jack and spare tyre. All you need to do is pull it out and disconnect the wiring from the terminal cup.

How is the rattle's?When you put a sub in your car, expect it to rattle! Although in saying this, i was actually quite surprised, the only thing that rattled was my back spoiler.

How does it sound? It sounds awesome! It is hard to compare this to the sound my sub would produce if it was in a normal wooden box, but from what i can hear everything sound wise is perfectly normal.

Last edited by marcs_sp20; 08-11-2018 at 11:30 PM.
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Old 26-04-2009, 08:05 PM   #2
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awesome write up!

I'll deninitely trying this in a few months!!

I think this should be made a sticky
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Old 26-04-2009, 08:34 PM   #3
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thats a great DIY job, looks nice and tidy too! well done.
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Old 26-04-2009, 09:54 PM   #4
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awesome writeup mate, i should point out that if you use a flece blanket instead of a cotton one, it replaces one layer of glass, as it itself hardens with resin im gonna make one for the 2/3 foldown pannel
how is the bass BTW i have the same sub only my current box is ported so its annoyingly loud
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Old 26-04-2009, 10:13 PM   #5
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fleece blanket huh, i might add that in . My kicker sub also has annoyingly loud bass, i couldn't even imagine it in a ported box. I played with my settings a little bit and now got the bass just where i want it.
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Old 26-04-2009, 10:25 PM   #6
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ye its essentially same thing, it just hardens with the resin apparently like fibreglass and leaves a good finish surface for painting/vinyl providing that layers of matt are applied from the inside of the box. i never used it my self, but i read a few things bout it and it in a few car show once in which they used the fleece and only one layer of glass to make a roof lining of a car for tv screens, i think it was pimp my ride

ye adding a port would make it louder and drony i dont like my box cus of the MASSIVE port AND cus its very huge and annoying

edit
i just googled fleece + fibreglassing AGAIN and its prefered because it soaks resin good and dosnt crinkle much
hope that helps man
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Old 26-04-2009, 10:50 PM   #7
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its a good sub...but maybe its time for a new sealed box . If you are gonna get a new box cause you don't like droniness, get a small box because they produce more clear and responsive bass than the larger ones . I'll re-edit the how-to to include your info on fleeces.
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Old 27-04-2009, 11:26 AM   #8
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I have basically the same woofer in a ported kicker box and its only 32L capacity, and the amount of bass I get outta the thing is unbelievable!

Im just waiting on Mat to take some pics of his woofer box (in the same position but made out of MDF for the back), so then I can make a box up and have just a fibreglassed front

Cheers
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Old 27-04-2009, 01:08 PM   #9
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Excellent Tute !

I would recommend something stronger than velcro to hold the box in place.
maybe some metal clasps so that it can still be removed easily
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Old 27-04-2009, 01:52 PM   #10
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cheers,

you would expect Velcro to be weak....but it actually holds onto the box really well. Ive done a lot of driving since i put the box in and there has been no movement. You're idea of the metal clasps though would obviously kick Velcro's ass

But think of it this way, the Velcro doesn't do much at all, its actually the tight fit of the box that holds it in nicely.
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Old 27-04-2009, 04:18 PM   #11
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velcro is perfec there IMO, becasue it holds VERY well on sidewards shear (ie holding a object from sliding if velcro is on sliding surface.) id suspect that the glue that holds the velcro on would give way before the actual strip
but yes metal clamp is the BEST way to go (kinda what i have now only its a bracket not a clamp but its ugly az :'()
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Old 28-04-2009, 08:06 AM   #12
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Wink increase your bass

I would line the inside of this box with dynamat so as to give that sub some thing firmer to reflect of which will increase your bass
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Old 04-06-2009, 09:17 AM   #13
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MY 2c's>IF U DO GET ITCHIE FROM DOING THIS JUST WASH THE ITCHIE AREA WITH COLD WATER AND SOAP(EVEN BETTER IF UR A REAL MAN)JUST HAVE A REALLY COLD SHOWER WITH SOUP AND A LOWFAR WHAT EVER THAT POOFIE THING IS CALLED(WOMEN USE IT)I USE IT AND THAT WILL GET RID OF IT:P
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Last edited by Rupewrecht; 04-06-2009 at 09:34 AM. Reason: no need to quote the whole post! and USING CAPS IS YELLING...
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Old 04-06-2009, 11:09 AM   #14
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Quote:
Originally Posted by so fresh View Post
MY 2c's>IF U DO GET ITCHIE FROM DOING THIS JUST WASH THE ITCHIE AREA WITH COLD WATER AND SOAP(EVEN BETTER IF UR A REAL MAN)JUST HAVE A REALLY COLD SHOWER WITH SOUP AND A LOWFAR WHAT EVER THAT POOFIE THING IS CALLED(WOMEN USE IT)I USE IT AND THAT WILL GET RID OF IT:P
CAPS much?

Washing powder works wonders as well...
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Old 04-06-2009, 11:15 AM   #15
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As does laundry detergent
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Old 04-06-2009, 10:24 PM   #16
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Very nice!
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Old 05-06-2009, 11:21 AM   #17
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As does laundry detergent
may aswell buy a bottle of whiteking bleach! lmao!!
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Old 05-06-2009, 11:34 AM   #18
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lol i meant the powder that is in small beads, it scrubbs good, and helps lift out the small fibreglass nedles "-
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Old 16-12-2009, 05:33 PM   #19
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Wink Sweet i like it

i have the same car exactly but my rear seats go up nd down nd gets used a lot nd was wondering if there is anyother place for the amp to go?

thanks mate nd nice post

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Old 16-12-2009, 06:50 PM   #20
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under the passangers seat??
or if u wantto get creative on the opposite side of the boot, FRP in nicely
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