# Custom Sub Enclosure For Trunk Floor



## ToplessBunny85 (Jan 6, 2009)

Hey all! I've got an 85 Cabriolet and anyone else who owns one knows how they're sort of lacking in the trunk space department. I currently have one 12" subwoofer in a ported box, but it takes up literally half the trunk. What I would like to do is build a nice solid plywood trunk floor and mount the sub into the floor, using the spare tire well as the space for the speaker to sit in so I won't have to raise the floor at all.

Now I have no problem making the floor and mounting the speaker and such, what I'm looking for is some advice on sound quality. If anyone has any advice on how to get a good solid, clean sound without anything rattling or distorting that'd be great! I want to make this enclosure, but if my sub is just going to sound like crap there isn't much point now is there?


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## boonedubbin (Oct 31, 2009)

Use 3/4 inch MDF for all wood components.
make sure your enclosure meets the volume reccomendations of your sub woofer.
Dyna mat your whole trunk.


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## John Reid (Jun 30, 2010)

What boonedubbin said. 

And, a sealed box will generally sound better than a ported box (unless the ported box was made by someone who knows how to make them properly, which many people don't.. they're an exact science).

You mention that you don't want to raise the floor at all... that could be an issue.

The key point here is that your sub needs a specific amount of airspace to work properly, so you need to make sure that you have enough room in the spare tire well to match that. 

You can look up the specs for your sub online if you don't know them.

And you can find out the approximate airspace in your spare well by using packing peanuts. 

What I do is:

- make a .5 ft square cardboard box to use as a "measuring cup". 

- fill the enclosure I'm working on with the peanuts

- scoop the peanuts out with my .5 sq ft measuring cup to get an *approximate* volume.

If the sub you own requires more airspace than you have to work with, you'll either need to get a sub that is designed for a smaller airspace, or make a bigger enclosure for your existing sub by raising the floor of the trunk.


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## ToplessBunny85 (Jan 6, 2009)

Awesome, thanks for the tips. I never would have thought of the packing peanut idea.  Appreciate the help!

And yeah I was too lazy to build a box for my sub so I just bought a ported one because I knew it was going to be temporary until I managed to get the time and materials to do the floor idea. I'm hoping I won't have to raise the floor, but if I have to I will. It'll still give me more room than I have now. Hahah.


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## John Reid (Jun 30, 2010)

No problem... used that tip back when I was installing in the early 90's. 

It's not exact, but works well for odd shapes.

Good luck!


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## thecyclonewarrior (Sep 25, 2002)

I did this EXACT same thing with my now gone GLi. ONE HINT though, no matter how much dynamat you put in the trunk and spare tire well, you CANNOT stop it from actually flexing when the bass hits. 

My brother and I raised the floor of my jetta so it was even all the way across the back with the sides of the trunk in the jetta. Sectioned off an area at the very back just large enough to put the amp and electraonics down onder the lid as well so all hidden, and installed 2 10" DVC cerwin vega's. We could never get it tuned right, and one day, my brother was laying on the driveway feeling out rattles, and exclaimed HOLY CRAP when he saw that the tire well was actually FLEXING every time it hit.

So if you go this route, make a 3/4" MDF circle piece, and seal it to the bottom of the well. Make it fit as tight as you can in the very bottom, tons of liquid nails so no rattling. We then put vertical braces along the sides of the well, liquid nailed and screwed through the well sides so they would not flex, and walla, major boom with a still usable trunk with the covers on the 10s. 

Just sharing my experience so you can learn from my mistakes

Bruce


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## John Reid (Jun 30, 2010)

Yeah, I actually assumed he was going to fiberglass an enclosure, using the spare well as a form...


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## buggydubbin (Jul 3, 2009)

yea you gotta glass it. i tubbed out my whole trunk in 84 rabbit. its a 7.7 ft^3 enclosure tuned to 29 hz for a single 18. it sits even with the top of the back seat.


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## Pat @ Pitt Soundworks (Nov 14, 2008)

For this type of install I wouldn't waste my time doing a sub install in the trunk. I haven't worked on a Cabriolet, but what you can do is put a sub in the front seat passenger foot-well underneath the dash. This way it doesn't take up too much space and you can fit up to a 12" sub. Because you have a convertible, you don't have any cabin gain, and need as much surface area and need to be as close to the listener as possible.


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## John Reid (Jun 30, 2010)

Duh, I totally spaced that a Cabriolet is a convertible...


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## lilred86 (Sep 3, 2011)

*Late to the parade*



Pat @ Pitt Soundworks said:


> For this type of install I wouldn't waste my time doing a sub install in the trunk. I haven't worked on a Cabriolet, but what you can do is put a sub in the front seat passenger foot-well underneath the dash. This way it doesn't take up too much space and you can fit up to a 12" sub. Because you have a convertible, you don't have any cabin gain, and need as much surface area and need to be as close to the listener as possible.


Wow. that's an outstanding idea. I know this thread is 7 months old, but bump for an awesome thought. Any Pics or specs out there of an install like this?


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