fiberglass box

Fiberglass  is an art. after you get it down how to do it. practice practice. it depends how you are doing you box. if you are using a spare tire well for your cubic volume. you make a fiber glass mold of your spare tire well. but if you are doing it like the one in the lexus. build an outer shell of mdf. make sure that outer shell is braced very good inside. then make a couple of speaker rings for the speakers you are using. after that make sure you have you fiber glass resin, mekp, fleece, fiber glass mat, and bondo. make you shape with your rings in your design. then you fleece the whole design and staple it to the mdf board. then mix half bondo and resin together then add mekp. paint it all over the fleece. make it thick. it will probally take a couple of cups of it. wait till it drys. sand it down and it ready for paint. then add the fiberglass resin and the mat inside the design to add bracing and flexing. any more questions. add another topic.ohio top first class installer

I find it's easy to form the mold out of styrofoam, place speaker rings of wood on it  and cover it with 7 or 8 layers of matte cloth and when it sets up remove the styrofoam with an acetone solution, it leaves the box empty and ready to cut out holes

Building the fiberglass box like the one you pictured is fairly simple. Everyone does it a little different, both previous posting are good ways to go. Simply construct the MDF portion(4 sided box) and rout out the speaker rings. I like to make my speaker rings from 1" MDF and a little over size. I then cover them with 1/2" MDF and rout them flush to the 1" rings and then rabbet them to where the speaker would sit flush. I then rabbet the out side of the rings to leave a "step" to staple the carpet / matting to. Theis leaves the opening perfectly round and you spend less time sanding and finishing. My only other prefference is to use regular speaker box carpet, the grey or black stuff, instead of fleece. It's cheap it forms well and doesn't droop or leak as much resin as fleece. then matt it a couple times, usually like to glass the back side at least once as well. I like to build my glass up at least a 1/4" thick. Then simply shape fill the imperfection with bondo and sand till you can't breath anymore, then repeat the entire process until you're happy. Good luck!! I suggest practicing on some kick panels first.