C300 custom sub box (homemade)
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Joined: Oct 2010
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From: South Jersey
08 C300 Sport
C300 custom sub box (homemade)
I've seen a bunch of stereo threads recently and thought I'd show you guys the project I just started tonight. Everything is being made from 3/4" MDF and I'm going to fiberglass it all and get it sprayed once I'm finished. This isn't my first time building a box, but it's my first with this kind of complexity and I've never fiberglassed before. Join me in my journey 
I pulled my 10W7 and JL 500.1 amp out of my truck and think it'll be a mean combo for the trunk of my C.
I set them in there and started thinking:
Came up with an idea:
Started to go from there:
And an idea of where the W7 will sit and fire from:
I've got about 3.5 hours worth of work into the box so far. I think it's coming out pretty well, all original and my first box in a trunk, and also my most custom box. I wanted to go all out for the Merc brand
I know there may be gaps in these pictures, all that will be taken care of, still have a lot of ends to button up, but I wanted to share my progress!
I'll be sure to post in here as I get farther. Time for some sleep
I pulled my 10W7 and JL 500.1 amp out of my truck and think it'll be a mean combo for the trunk of my C.
I set them in there and started thinking:
Came up with an idea:
Started to go from there:
And an idea of where the W7 will sit and fire from:
I've got about 3.5 hours worth of work into the box so far. I think it's coming out pretty well, all original and my first box in a trunk, and also my most custom box. I wanted to go all out for the Merc brand
I know there may be gaps in these pictures, all that will be taken care of, still have a lot of ends to button up, but I wanted to share my progress!
I'll be sure to post in here as I get farther. Time for some sleep
Last edited by 08SEA300; Nov 17, 2010 at 08:06 AM.
Senior Member
Joined: Aug 2010
Posts: 473
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From: PA
2012 E350 4-matic SPORT
looking good.
I got my car in the shop right now. im getting 2 13tw5 in the trunk plus other stuff. I didnt get no fiberglass it was out of my reach$$. I hope i like what they did with the sub box. I'll post a thread tomm
I got my car in the shop right now. im getting 2 13tw5 in the trunk plus other stuff. I didnt get no fiberglass it was out of my reach$$. I hope i like what they did with the sub box. I'll post a thread tomm
Thread Starter
Member
Joined: Oct 2010
Posts: 198
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From: South Jersey
08 C300 Sport
Everything I've used so far can be picked up at Home Depot. Fwiw, I started with raw 2'x4'x3/4" MDF sheets and went from there. It all prices the same and it's not as cumbersome as working with a 4x8 sheet.
Last edited by 08SEA300; Nov 17, 2010 at 08:06 AM.
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Joined: Jan 2009
Posts: 238
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From: Montreal, Canada
2011 E550 Coupe
I have two concerns here. First, that is a lot of weight to add to one side of the car, I would think it would be preferable to have is centred in the rear of the truck or on the right side to offset driver weight. Second, hope you never get a flat tire.
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Thread Starter
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Joined: Oct 2010
Posts: 198
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From: South Jersey
08 C300 Sport
The fiberglass is just a different medium to finish with. Up until now I've only built solid MDF boxes. Some people swear by all wood, others mix, and some others build all fiberglass. It's really a preference and any material works well, as long as it's thick enough and braced correctly.
Speaker weighs 30 on it's own, and the amp might weigh 10-12 pounds at most. Box might weigh another 10 about. I'll be generous and say that I'll be adding 60 pounds to that side of the car. I don't see it effecting the car that much, this kind of speaker set up is done very often. Also, I don't weigh too much myself, so I think I'm just offsetting my potential weight with the box now
The box will be able to be moved in case of a flat. I live in Jersey and some of the roads are less than pleasant, so I thought of that as well.
Before anyone asks, I left enough room to change the rear light bulbs as well, but once again, the box can easily be removed for that change as well.
Thanks for the concern! Definitely open to critiques.
The box will be able to be moved in case of a flat. I live in Jersey and some of the roads are less than pleasant, so I thought of that as well.
Before anyone asks, I left enough room to change the rear light bulbs as well, but once again, the box can easily be removed for that change as well.
Thanks for the concern! Definitely open to critiques.
Last edited by 08SEA300; Nov 17, 2010 at 08:17 AM.
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Thread Starter
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Joined: Oct 2010
Posts: 198
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From: South Jersey
08 C300 Sport
Made some more progress last night, thought I'd share. I know it doesn't look "pretty" but I needed to seal the seams and a few other things to make sure I had structural support and no air gaps.
Got the speaker ring mounted in place:
Couldn't help myself but to make a test fit in the car:
Just did a test fit with the sub this morning:
The amp will sit down about a level with "audio" in JL audio once mounted in place, but this was just to give an idea.
This is coming together pretty well! Let me know what you think!
Looking forward to making some good progress throughout the next week. I have the wiring and everything bought and ready to go.
So far I have about 7 hours into the box all together.
Got the speaker ring mounted in place:
Couldn't help myself but to make a test fit in the car:
Just did a test fit with the sub this morning:
The amp will sit down about a level with "audio" in JL audio once mounted in place, but this was just to give an idea.
This is coming together pretty well! Let me know what you think!
Looking forward to making some good progress throughout the next week. I have the wiring and everything bought and ready to go.
So far I have about 7 hours into the box all together.
Last edited by 08SEA300; Nov 19, 2010 at 08:25 AM.
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Joined: Sep 2010
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C350 CDI Sport
This would be my concern too....that sub is going to move some serious air.....right into the top of the trunk.....perhaps it should be half the height.
I would also reinforce the uprights with some more support too...its surprising what goes on inside an enclosure.....
Good luck with the project..
I would also reinforce the uprights with some more support too...its surprising what goes on inside an enclosure.....
Good luck with the project..
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Joined: Oct 2010
Posts: 198
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From: South Jersey
08 C300 Sport
Got inside and measured, the trunk lid actually goes up in that particular area where the sub is sitting, so it worked out well.
I sealed the seams with a $3 squeeze bottle of caulk. It was tile/tub caulk, anything will do, just to make sure air won't get out.
Today's project was wrapping it in fleece and putting on a coat of resin.
This would be my concern too....that sub is going to move some serious air.....right into the top of the trunk.....perhaps it should be half the height.
I would also reinforce the uprights with some more support too...its surprising what goes on inside an enclosure.....
Good luck with the project..
I would also reinforce the uprights with some more support too...its surprising what goes on inside an enclosure.....
Good luck with the project..
Here's some more updated pics from today-
Fleeced the box first:
The usual test fit/tease of the final idea for myself:
Here's the box after I soaked it with resin:
Finally starting to see the final image, I'm liking what I see. Hope you guys do too
Thread Starter
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From: South Jersey
08 C300 Sport
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Joined: Jan 2009
Posts: 238
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From: Montreal, Canada
2011 E550 Coupe
Don't want to be negative but I don't think you'll like the sound with that sub blowing into the trunk lid. Trunk lids are notorious for rattling, it may sound ok from inside however it will more than likely sound horrible from outside. I would of put the sub perpendicular to the floor and facing towards the back seat in that curve you have in the wood. Hope it turns out good for you because these boxes are a lot of work.
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Joined: Oct 2010
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From: South Jersey
08 C300 Sport
Don't want to be negative but I don't think you'll like the sound with that sub blowing into the trunk lid. Trunk lids are notorious for rattling, it may sound ok from inside however it will more than likely sound horrible from outside. I would of put the sub perpendicular to the floor and facing towards the back seat in that curve you have in the wood. Hope it turns out good for you because these boxes are a lot of work.
Something I experimented with before in my last car was sub placement, and the best in car response was by the trunk lid. Also, having it here and pointing up will protect it if I do ever use the trunk for storage duties.
Thanks for the concern! I too am hoping that I don't fall victim to the "rattle trunk" sickness of most beginner stereo installs.
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From: South Jersey
08 C300 Sport
Thank you!
I used polyester fleece to cover it and than coated that in resin. The resin didn't work out as planned, the polyester soaked up a LOT of it. Way more than expected. So I went over to my friends house, and he works for a guy who makes props for amusement parks, and I laid #2 fiberglass on it with professional resin, and we'll just say that the box will probably be stronger than some of the cars components 
Here's the latest pics with the new layers of fiberglass and resin in place-
No- it's not at the pretty looking stage yet.
From here it's sanding, body filler, and than paint. Things to look forward to next week
Here's the latest pics with the new layers of fiberglass and resin in place-
No- it's not at the pretty looking stage yet.
From here it's sanding, body filler, and than paint. Things to look forward to next week
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From: Norte America
MBUSA
Keep up te good work. Are you going to run power and ground directly from the battery and tap one of the rear speakers? Any other components like a cleansweep?
Btw, if the trunk starts flexing I guess you can always turn it on it's side (largest MDF piece on the floor)...just a suggestion.
Btw, if the trunk starts flexing I guess you can always turn it on it's side (largest MDF piece on the floor)...just a suggestion.
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Joined: Oct 2010
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From: South Jersey
08 C300 Sport
Keep up te good work. Are you going to run power and ground directly from the battery and tap one of the rear speakers? Any other components like a cleansweep?
Btw, if the trunk starts flexing I guess you can always turn it on it's side (largest MDF piece on the floor)...just a suggestion.
Btw, if the trunk starts flexing I guess you can always turn it on it's side (largest MDF piece on the floor)...just a suggestion.
You got it right, I'm running direct for the best power and cleanest run, simplest too. Have the JL audio wiring pack, I'm normally not a package deal guy, but it had everything I need and I like that I'm running all JL equipment and accessories in the end.
I'm actually going to install a re-Q. It was recommended by a friend of mine who does high end stereos and I really like that it senses the stereo and adjusts the sound accordingly.
If my trunk starts flexing, I'll start with the dynomat, but I do like your suggestion of flipping the box if it's really needed. I could even flip it and tuck it by the back seat if it got all that bad.
I'm looking forward to this weeks progress, try and knock out some solid work and have it running by the end of the week, we'll see though. That's the plan as of now
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From: South Jersey
08 C300 Sport
I'm sure you could do it if you got your hands on the right tools
Updates from today- sanded the box down, ran into an issue with the amp fitting just right, didn't allow much for the fiberglass when I built the amp shell. So I had to modify the box and didn't get to the body filler today. I did get it sanded the way I liked, and fixed a few softer spots that were left.
Tomorrow should be body filler and if all goes right, I'm going to try and drop it off to my paint guy tomorrow night, but I'm not rushing anything.
Today's pics:
Amp finally in place-
You can see how I took it back down to the wood here-
See what tomorrow brings
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From: South Jersey
08 C300 Sport
wow, didn't know there may be a demand for the box.
It's taking a little longer to shape the body filler than expected, I'm a bit ****, but at the same time, it has to be perfect before paint. I have over 2 hours in sanding alone.
Pricing, I wouldn't even know where to start. Being my first time making a fiberglass box, I have about 10-15 hours into the box so far. If you are seriously interested, there's a lot of variables for the box, speaker, cubic feet needed, amp placement, etc. But if you really really want one, we might be able to work something out.
Here's yesterdays picture. As I said, it's not anywhere near where I want before paint, but it's getting there.
Hopefully next week will be the final week- today, it's a day to be thankful for everthing! Have a great Thanksgiving!
It's taking a little longer to shape the body filler than expected, I'm a bit ****, but at the same time, it has to be perfect before paint. I have over 2 hours in sanding alone.
Pricing, I wouldn't even know where to start. Being my first time making a fiberglass box, I have about 10-15 hours into the box so far. If you are seriously interested, there's a lot of variables for the box, speaker, cubic feet needed, amp placement, etc. But if you really really want one, we might be able to work something out.
Here's yesterdays picture. As I said, it's not anywhere near where I want before paint, but it's getting there.
Hopefully next week will be the final week- today, it's a day to be thankful for everthing! Have a great Thanksgiving!
