i want an extrememly sturdy box for my 18's

[bobtista 10+ year member]

i'm doing a build for 2 hdc3 18's in a 94 jeep cherokee 2dr off an ap3000d and i need to know how thick of mdf i should use, bracing options, baffles, etc. to prevent the box from moving. i dont need overkill, just enough where my box wont flex and i wont have sound lost in the enclosure due to the wood resonating. the box will be 13.5 cubes before port/sub displacement tuned to 38hz. this is my first big car/big box build so i'm not too sure. i have the use of fiberglass also. should i glass the inside?

help please.

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[bobtista 10+ year member]

i got a few views, but i need some positive input. i know someones built a box for 2 18's in an suv. someone help!

 

[gotparts90 10+ year member]

what shape is the box gunna be? lots of bracing like threaded rod or dowels is great. To save weight over a double baffle and make it stronger a 2x4 or 2x5 running along the large flat boards makes them super stiff. fiber glassing flat panels makes little sense to me and just adds lots of weight and cost for little strength gain. fiberglass is strong in curves but flat it very weak. I would take a well braced construction over thicker wood. Also try birch lighter and stronger.

 

[bobtista 10+ year member]

what shape is the box gunna be? lots of bracing like threaded rod or dowels is great. To save weight over a double baffle and make it stronger a 2x4 or 2x5 running along the large flat boards makes them super stiff. fiber glassing flat panels makes little sense to me and just adds lots of weight and cost for little strength gain. fiberglass is strong in curves but flat it very weak. I would take a well braced construction over thicker wood. Also try birch lighter and stronger.

do you mean attach 2x4's horzontally in the middle of each wall of the box?

 

[bobtista 10+ year member]

what shape is the box gunna be?

it will be rectangle and the dimensions will roughly be 18 tall 44 wide 43 deep

port back subs up i assume

 

[mlstrass 5,000+ posts]

use baltic birch as it's much stronger then MDF. Double baffle and do port in the middle/rear firing as it will add bracing. You can then do some strap bracing on the walls and call it a day.

I've done numerous boxes like that for 2 18's and have never had any flex issues...