So lets get to it already!
Carpet:
Always use a high quality application specific carpet. DO NOT use house carpet or anything thats not designed for this application.
Vinyl:
DO NOT wate your money on the crap vinyl at your local fabric store. It doesnt work well for our application. Once again you want application specific material.
Glue:
I used 3M Super 90 glue. Its about $10 a can and I can usually get 1 1/2 boxes per can. Follow the directions on the can. I spray heavy...
How to:
First thing is first. Set the box down and size the carpet to it. In other words, make sure its going to wrap the three sides and at LEAST 2" on the bottom. I never carpet the bottom as you dont see it anyhow, why waste time?
I glue the side with the holes for the speakers first. Be advised to follow the glue makers instructions for permanent bond. This usually requires heavy spray on both the carpet and box. ONLY spray the surfaces your working on!
Image shows first side glued and the bottom lip glued and stapled to the box. The process is simple: Roll the box on a side your not about to glue. Spray the glue on the box and carpet ONLY in the areas you want to glue currently. Flip the box over on the floor and push DOWN. Pull the carpet so there is no wrinkles. It is important to staple it to the box so you can pull the carpet tight.
Gluing the second side. As you can see you just keep glueing and rotating the box while doing so. Remember to PULL the carpet tight. This pulls wrinkles out and makes sharp crisp corners. I tend to sit on the box for about 2-4 minutes to hold it after pulling.
Glueing the final side... Dont forget to glue and staple the final lip down!
Next I take a NEW razor blade and cut out the holes. You should hold and pull the carpet while cutting. This creates smooth cut lines and no fraying of the carpet. Please note to use a NEW razor!
The begining of the Ends...lol Seriously this is where everyones trouble starts. Sit the box up on end, the other side will be temporarly crushed. Providing you pulled the carpet tight, sat on the box and let the glue dry it should be FINE. Ok, this picture. Take your razor and cut two small areas where the corners are.
Next take the razor and just cut as staraight as reasonable that whole line. It should fold down like a flower. The more accurate you are on the corners the better the end result. FYI its not super important to be highly accurate here.
Mark a small section in the center of the box. I usually use 2".
Next cut the top flap into a sort of triangle. Except you want a 2" tab at the bottom. Please look closely at the pic. This flap folds and glues to the bottom. Glue and staple this piece down. Make sure there are no wrinkles.
Next fold in a side. Survey where the glue needs to go. Spray the glue on and press it down tightly. Next take a straight edge and push it all the way untill you feel it hit the edge of your first triangle. Hold it there TIGHTLY for a minute or so for the glue to dry.
While holding the straight edge against the first tab take that razor and cut along the straight edge. The tighter and mroe accurate you have the straight edge to the first triangle, the better the cut and look. You can see in this picture mine is fairly close. Expect to have some trouble doing this, not that easy. Make sure to make a small tab for these side trangles. Fold it down, glue it and staple it...
Another end pic of box in progress.
The final result. I used a black paint marker to cover the cracks where the carpet inst exactly there. It makes these seams very stealth and looks good in the end.