box design help 2 btl 18's

[M82a1snake 0]

i have two btl 18 fully loaded daily, im getting two cresendo audio 3kwp's amps, only part i dont know how and where to design the port at i want the port tuned to 32 hz, im doing the subs up firing , my external max dimensions are 45" W x 33" D x 23.5" H. i need help with port design and/or placement as in a port type crx, slot port, ect ect... which one do you guys think will have most output and will coincide with my box dimensions. . p.s. do you guys think the XS power 3100 is a good battery to run with this setup? along with the yellow top under the hood.

[hove 15]

your gonna want to make sure you do the BIG 3 aswell. i would suggest maybe 2X D3100 and a HO alt for sure. 2X Crescendo 3k is gonna draw alot of power man. make you you have the electrical to back it up. as far as the box goes. i have no idea about that lol i get mine built lol

good luck with ur install bro. dont forget about posting some pics and vids in a build log!

[M82a1snake 0]

oh and one more question since im having two btl 18's in a ported box the recommendations for one sub is 5-10 cu. ft. ,so for two subs it would be 10-20 cu.ft. now would it be ok if because port design makes internal cuft. of box around 12 cu. ft.? and would it still be considered a around a 16 cu. ft. box since its about 16 cu. ft. including the port space so basically what im asking is do you calculate the port space in with the internal box space to see how it matches up to the recommendations?

thanks for all the help in advanced!!

[M82a1snake 0]

where do you get your boxs built at just curious.

[streetbeater07 0]

Im sure Fi's specs for the subs are EXCLUDING PORT AND DRIVER DISPLACEMENT. The numbers you are referring to is the amout of airspace that the woofers MUST have in order to perform to their potential.

[tejcurrent 13]

Step one: figure the internal dimensions of the box. Example: if you box is 49" wide x 19" high x 38" deep on the outside, subtract the width of the mdf. Assuming single layers of 3/4 mdf that gives you 47.5 x 17.5 x 36.5. This comes out to 17.558 feet.

Step 2: figure out your port. With 14 feet net you'll want about 190 square inches of port. I would do a slot port along the bottom of the box, but with a divider going down the center. This will give you 2 ports 4" h (internal) x 23.375"w x 28" deep. The top layer of mdf takes up box space too, so to figure out the entire amount to subtract from the net volume figure (4 + .75) 4.75" H X (28 - .75) 27.25" D X 47.5 W = 3.558

Step 3: Now subtract that from 17.558 and you get your net volume, which is 14 feet.

Step 4: Subtract all bracing and subwoofer displacement for the actual final volume. After subs and possible bracing you'll be looking at more like 13.5, but other than lowering your box volume it will raise tuning slightly to around 33hz.

I don't know your actual dimensions I just went off of what would fit well in my tahoe.

You'll also be fine using 12 feet net, but I would really build around what sort of sound you're looking for unless space is an issue. I build my own boxes, and spend a lot more time on the math than I did for this quick example. The more time and work you put into it the better your outcome will be. You really only need a saw (or you can get lowes/home depot to do cuts) glue, and screws and screw gun or finish nails and a nailer. Clamps help too.

Also you'll really want to double baffle your box.