I am looking to either build a couple custom sub boxes or perhaps find someone that makes those custom plastic molds for the trunk....I am curious as to what kind of material is best for the boxes? There may be certain stuff in other threads but figured this might organize it all into one perhaps.....

I made my box out of 3/4" MDF. It's really strong stuff, I'm running 1200W to 2 12" audiobahn subs and I didn't bother adding any internal cross bracing because I was lazy. Turns out I didn't need it anyways because the box doesn't flex when I crank it up. Of course it probably weighs around 100 lb with the subs in it.

The number one choice is 3/4" MDF (medium density fibreboard). It works great and is very easy to work with. Birch is almost half the weight of MDF, has the same properties as far as resisting vibration as MDF, but costs about double. Plywood will work ok, but the sound quality isn't as good. Plexiglass looks very nice but can be a real nightmare to work with.

I feel dumb here but what is MDF and also what is better to use as a sealant?

Ahh ok thanks, hopefully I will get a chance to run by the local Home Depot and build these here in a couple weeks....

I don't know that I've ever heard of someone using any sealant other than silicone.

I was just curious because I stopped by my local audio dealer and they had a couple boxes close to what I want and it had some kind of sealer on the inside, perhaps a cement or something? The same store also had a sweet Tiburon on display with Infinity sponsored system including about 6 LCD screens (one in the trunk, two on both doors, a couple on the seats, and one on the dash) the paint scheme was real simple, and had a sweet looking custom plastic mold in the trunk for the two subs and the LCD screen, unfortunately I dont have a phone that can take pics....

MDF = Medium Density Fiberboard. Home Depot has it in 4'x8' sheets. About $20. Unless you're building something huge, that full sheet will be enough, but figure out the dimensions of each panel for your box ahead of time because they'll cut it six times for free and then $.25 for each additional cut. So you can have them do a lot of the work for ya...not to mention making it so that you can get that 4'x8' home without a truck.

Sealant of choice on many forums would seem to be Liquid Nails or an equivalent. Screws every two inches or so also. Silicone isn't going to stick very well to wood or plexiglass. At least not well enough to stand up to the pressure inside the box.

From what I've seen about plexiglass, you'd need about 1/2" or better, which is quite expensive. And it is a PITA to work with and have it look good.

I'd suggest finding a big cardboard box and hack it up and build your enclosure out of that so that it fits in the car like you want and you get the internal volume that you need. That's what I did. Lots of measuring and trimming and recalculating in MS Excel.

I've got pieces of MDF sitting in the corner right now waiting to be trimmed and put together. :)

the "plastic molds" you refer to are most likely fibreglass enclosures, you cant make an enclosure out of plastic

Yea I meant fiberglass, my bad.....either way I bet its expensive for custom makes...yet alone finding someone who does that stuff....

thats the best method for sealing ur box.

figberglass enclosures are hella expensive too..... unless u know how ot do it urself

you also lose sound quality with fibreglass, but they look nicer...mine is half fibreglass and doesnt sound good as the original box did

fiberglass is not that hard too work with just takes a long time that is why people charge you up the ass for custom fiberglass work, try it yourself that is how i learned how to make custom enclosures....

I made a fiberglass box for my car it was pretty inexpensive if you read up on it on the net it is very simple. I will post some pics here sometime soon.

i know its a little off topic but has anyone put a sub in place of the spare tire. Just curious because it seems like a logical place.

sounds logical john, if you get something to hold it in place... not sure? never tried. i'm going to try that this weekend if i get the chance. but where would you put the spare tire...?

lol...thats a very good question..just hope you get lucky and dont get a flat...lol...i dont know.

I have my spare wheel place made into my box. I have it so it looks like a normal trunk but raise a few inches. I'll put a picture up later, it's rainy right now.

another ? then...how much room do you have to work with so that the top of the sub box lays flat with the rest of the trunk..or am i dreaming again?

I didn't do it myself, but to get it even with the trunk now i think you would be only able to only put 1 speaker in it and have to cut out the spare wire bracket.