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I'm going to attempt to build a sub box to fit into the passenger floor of an 80's Porsche 911. If you're familiar with that car, the passenger floor has a wood board that has an area behind it that has housed various things during the course of production, and in my case it has a junction box for the factory fader, which splits the 2 channel radio to 4 channels through common ground wiring. Since I'm going to be running new wires I can eliminate this stuff and I have an irregularly shaped space to work with. The board is big enough for an 8" subwoofer, and I'm planning on using a low profile sub that only requires around 3.5" depth. I know that I need to baffle it somehow and was planning on a sealed enclosure, but I'm not exactly sure how to come up with the dimensions or accurately measure the available space. I was thinking the simple solution would be to just seal the entire area behind the driver with Dynamat and tape and forego an enclosure, or use a foam baffle behind the driver. Both would be a compromise of course. I guess my question is if there's any kind of shortcut method to determining the what's going to fit if I build a box without trial and error. The system is nothing too elaborate, upgraded speakers in the factory locations (4x6 rear, 5.25 doors) and 5 channel amp.

Thanks!
 

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Depending how irregular it is (I'm not familiar with that car sorry mate!)...you may want to (or have to) do a fiberglass enclosure...I don't think it is THAT difficult (I have never done one); but it is a little harder than gluing and screwing MDF together...might be an option...
 

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You don't need to go the enclosure route if you can seal off a baffle good enough:
274013


Edit, 2nd picture did not load:
274050


Ge0
 

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Discussion Starter #4
I was thinking something along those lines. Dynomat the entire area behind it and put a little damping material over it, and install a rubber gasket around the outside of the floor board. It might not seal completely but I'd be able to tune it by the amount of damping material or porting the board itself. I'd definitely have much more volume than I would by making a complete enclosure.


You don't need to go the enclosure route if you can seal off a baffle good enough:
View attachment 274013

Ge0
 

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I was thinking something along those lines. Dynomat the entire area behind it and put a little damping material over it, and install a rubber gasket around the outside of the floor board. It might not seal completely but I'd be able to tune it by the amount of damping material or porting the board itself. I'd definitely have much more volume than I would by making a complete enclosure.
Precisely...

Ge0
 

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do you use your rear seats at all? Rod Birch is a well known installer from CA that's regarded well on Rennlist that bulids essentially a baffle for the rear foot wells behind driver and pass seats for 911's. I know he has them for 993/964, perhaps a design like that would work in your case.
 

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Discussion Starter #7
I'm on all the Porsche forums and I did speak with Rod, who was very helpful. I gave careful consideration to his sub box and decided that I wasn't ready to give up the rear seats completely. I don't really use them for people, but I've had the need for all of the rear seat space, including the floor area. The car is also a very original 43k miler and I didn't want to bolt anything to the floor and go with anything too permanent. The sub in the floorboard isn't permanent (I ordered a new floorboard to use with the sub) and I hope it will do what I want to accomplish. The car has a pretty aggressive M&K straight sport exhaust and going big on hifi is only going to get me so far. The main thing I was looking for was some bottom end so I can roll off the low end on the smallish main speakers. I'm not a bass freak so I hope the 8" in the floor will cut it for me with some good power behind it.



do you use your rear seats at all? Rod Birch is a well known installer from CA that's regarded well on Rennlist that bulids essentially a baffle for the rear foot wells behind driver and pass seats for 911's. I know he has them for 993/964, perhaps a design like that would work in your case.
 

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well at least you were familiar with the option. I also decided against a sub in mine, tooks Rods advice and used Hertz XL 2way since at the time they were one of the better performing 6” with decent lows compared to his other suggestion of comparable focals. I will admit that the stereo is nice, but the Fister mufflers are much better and to you point will drown even the best of systems
 

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I have been toying with the idea of making my own passenger floor board subwoofer. Here was a thought I had....

1) use expanding foam to capture the area
2) use that to create a mold...not sure what would be best approach for that.
3) create the fiberglass enclosure from the mold.

Why? Because I'm scared to death of having an accident while fiberglassing inside my vehicle
 

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Expanding foam sticks like crazy, I don't think that is any better than fiberglass resin.

Tape off and use lots of plastics sheets covering everything and you should be good to go with fiberglass.
 

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I would try it using the whole thing, if that does not work you can make an enclosure. Another idea is I had a car with a single sub box and amp on the box. I use a trailer plug to hook it all up and strap to hold it. Then when I needed the room I just unplug and leave it at home. It worked better than I thought.

I've done a hole with plastic bags and foam and packaging stuff to fill it.
 

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Doing one of these exact cars as we speak. Just left the shop otherwise i'd take a look for you. This customer supplied some really shitty "enclosure" that goes in the footwell of the rear seats. Its just a baffle that seals to the carpet. I'll report back on how it sounds.

That said, don't you dare bring expanding foam anywhere near this car. If fiberglass scares you, then expanding foam should haunt your entire existence.
 
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Thanks for that. There was a guy I saw years ago that made it look simple. Guess it isn't. I had thought about trying the instapacks used for shipping boxes... Guessing it's still a bad idea?





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Thanks for that. There was a guy I saw years ago that made it look simple. Guess it isn't. I had thought about trying the instapacks used for shipping boxes... Guessing it's still a bad idea?





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Fiberglass is easy. All you gotta do is cover nearby surfaces. Expanding foam on the other hand is unpredictable, even messier than fiberglass, and will PERMANENTLY stick to/stain literally anything it touches.

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What Nick said. Fiberglass can be pretty easy. I use aluminum duct tape to tape off the entire area.
Then lay aluminum foil around the immediate area and tape it down.
Then depending on where I'm working I'll even drape drop clothes or towel over anything resin could even possibly get on.


Then use petroleum jelly or another mold release on top of the foil tape.

I use foil tape bc it's thicker than masking tape , resin doesn't stick to foil well, and it withstands heat better than masking and especially duct tape so when the exothermic reaction occurs, I'm not left with a sticky goopy mess from tape adhesive break down.

Then just lay down 3-4 layers. Let it cure. Get an idea where you want to position the baffle. Mock it up in car.

Then remove the mold. Trim away excess. Install baffle . Add more layers on the inside now that it's out of the car.

And finish however you want.

There are misc other steps but fiberglassing in general isn't difficult.

If you're concerned about dropping or dripping resin on rocker panels etc...when you're done laying the matting, just leave the cup in the car til it cures. That way it can't drip on its way out.
 

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I'm going to attempt to build a sub box to fit into the passenger floor of an 80's Porsche 911. If you're familiar with that car, the passenger floor has a wood board that has an area behind it that has housed various things during the course of production, and in my case it has a junction box for the factory fader, which splits the 2 channel radio to 4 channels through common ground wiring. Since I'm going to be running new wires I can eliminate this stuff and I have an irregularly shaped space to work with. The board is big enough for an 8" subwoofer, and I'm planning on using a low profile sub that only requires around 3.5" depth. I know that I need to baffle it somehow and was planning on a sealed enclosure, but I'm not exactly sure how to come up with the dimensions or accurately measure the available space. I was thinking the simple solution would be to just seal the entire area behind the driver with Dynamat and tape and forego an enclosure, or use a foam baffle behind the driver. Both would be a compromise of course. I guess my question is if there's any kind of shortcut method to determining the what's going to fit if I build a box without trial and error. The system is nothing too elaborate, upgraded speakers in the factory locations (4x6 rear, 5.25 doors) and 5 channel amp.

Thanks!
If you are building an enclosure like you would in a spare tire well, remove everything and clean the area, apply overlapping sheets of aluminum foil held together with 3" wide blue/green low adhesion painters tape.

Make sure that the foil is contoured to the shape of the area to your satisfaction, you can pickup a bottle of water based mold release from Tap Plastics or some other appropriate hobby store, take an inexpensive paintbrush and liberally paint all surfaces to be covered with glass, then let it dry.

I suggest setting up for making a right angle flange of glass around the perimeter of the enclosure for the purpose of attaching the MDF panel for which the woofer driver(s) will be mounted,

Once you have laid all of the lairs of glass you need (make sure it is thick enough for rigidity/strength), let it thoroughly dry, then take it out and remove all the aluminum foil and tape, you can rinse the mold release off the back of the enclosure with water and a light brush, now dry it off.

If all is well, you should end up with an enclosure that fits the area like a glove, and, is removable.
 

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I have been toying with the idea of making my own passenger floor board subwoofer. Here was a thought I had....

1) use expanding foam to capture the area
2) use that to create a mold...not sure what would be best approach for that.
3) create the fiberglass enclosure from the mold.

Why? Because I'm scared to death of having an accident while fiberglassing inside my vehicle
I would think twice about expanding foam. Check out one of my old build threads. Miserable fail...

Browse pages 5 and 6

Ge0
 

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Fiberglass is easy. All you gotta do is cover nearby surfaces. Expanding foam on the other hand is unpredictable, even messier than fiberglass, and will PERMANENTLY stick to/stain literally anything it touches.

Sent from my SM-G975U using Tapatalk
Yep. What Nick said...
274367


The center never dries thoroughly. It oozes all over. Some of this stain is still there 12 years later 😳...

Ge0
 

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Yep. What Nick said...
View attachment 274367

The center never dries thoroughly. It oozes all over. Some of this stain is still there 12 years later ...

Ge0
The center will dry if you use a 2 part foam. But those are hard to use and unpredictable

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The center will dry if you use a 2 part foam. But those are hard to use and unpredictable

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Two part cures without the need for air contact right? One part activates the other?

Ge0
 
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