It can be very difficult to get good results without a large autoclave to create a strong and air free part.
Now first off, I am no speaker builder, but I have heard many a person expressing desire to build cabinets out of carbon mat. I have built many gas tanks, seats and fenders for motorcycles from fiberglass and carbon, which have much more complex shapes than a speaker cab, so this should be no problem for a simple cabinet.
First off, you need a buck. Generally this is either made from wood or styrofoam. For gas tanks and other complete enclosures, I use styrofoam, as once the final piece is made, I can use gasoline to break it down to liquid and it is quick to shape. For a speaker cabinet, I will recommend this same process as well. You must make two that are identical.
Now, since this isn't a motorcycle part, and weight is not a factor, I would suggest first building it up with woven fiberglass mat.
Over your buck, lay alternating layers of resin and glass, making sure to use a roller to force out any possibly trapped air bubbles in the process. The baffle face should be layed very thick for strength, but for resonant properties, I'm not entirely sure of how thick the rest of the cabinet will need to be, that would be best left to the engineers here to figure out. I'm just a laborer.
On a buck, after laying your final layer of glass, test fit your carbon sheets, (compound curves can be tricky, and I don't recommend them for the beginner, Stick with a simple round-backed cabinet) once you are certain of fitment, lay your resin and mat, then top layer of resin.
Here comes the trick, after initial drying, but not fully cured, place playground sand into large metal containers at 400 degrees for 20-30 minutes. pull out and mix with equal part of room temperature sand. Cover all sides of part with heavy black trash bag and place in tub or other container large enough. Pour sand (should be between 120 and 140 by now, so wont melt plastic) and pour in all around wrapped part (should be flat face down). Let stand for 60 minutes, until completely cool. Put sand back into containers to repeat process for next part you are making.
The heat and weight of the sand forces the resin into the carbon weave, which is the trickiest bit, the resin penetrates and bonds with the fiberglass far easier. once pieces are complete, use your saw, or router, whichever you normally use to cut the holes for your drivers. once holes are cut, pour in gasoline, which will break the styrofoam down to a gel which can be poured out and PROPERLY disposed of.
After this, a run over with 800 then 1200g wet sanding will smooth it perfectly and a finish buffing with a cutting compound will polish it up beautifully for you.
This is seemingly a far better process for smaller bits, as a bookshelf speaker, but if you have the space, and money, a floorstander is exactly the same.
Hope this helped a guy or two venture out and build something new, good luck guys!
