Lightweight enclosure design ideas.

[bongobennie]

I am building two 1st gen Honda Insights, they weigh in the neighborhood of 1800 lbs. I also have a desire for bass but really want to have my cake and eat it too. I also have a good 3-4 cu ft to play with, just not the weight to match. So far I have found that birch is desirable but other than that, its not something most audiophiles care about (weight). I have been looking at building a fiberglass enclosure using the spare tire well as a permanent part of the box with a removable wood lid. In this set up, sealed wouldn't be too hard to figure out the resulting airspace and using subs to match but is it that simple to do with a ported box? For my next question size is irrelevant. What would be some ideas that keep the weight down and the beats loud (and somewhat clean)? 

[Triticum Agricolam]

If you can get some pine plywood with at least 7 plies (for 3/4" thick panels), its lighter than both MDF and birch.  The stuff I get is called Arauco plywood and I really like it.

Depending on how much power you are running, you can build out of 5/8" or even 1/2" and just brace it well.   A box built out of 1/2" material with bracing in the center of all the panels will be stiffer than the same size box built out of 3/4" material with no bracing.  

[06RTCharger]

I wonder how well a fully carbonfiber box would sound. Im sort of in the same area, wanting to keep it light as i can. My first idea is im going to attemp to seal off my trunk from the cabin and build a new carbonfiber reardeck as the baffle. For an infinite baffle setup. No real plans yet but thats an idea im going to try to figure out when i get to that stage of my build. 

[bongobennie]

Thanks for the replies. Im new to fiberglass and definitely new to carbon, I do however work with metal, I have thought about building a thin aluminum enclosure, then a slip fit thin wood inner liner.... no idea if it will work. I also like the sonotube ideas however the shape is rather inconvenient. I also like the idea of using the spare tire well as a permanent bottom half (2/3s actually) Lots of space, big cones and small magnets.