18 BTL Ported Box Calculations

[Frostedflakejake 148]

Alright, so i finally have all the pieces together for the btl. Alternator, battery, amp, wiring, ect.

So now to this whole... building my own box thing. i would prefer around 32hz and 7.5-8 ft^3 before

displacements for sub and bracing. I have 3/4 inch MDF (its actually 11/16ths). So one question is how do i brace it properly?

And... i need box calculations for a standard Sub facing up, port facing back of vehicle design. I really like Mac n' Cheese's idea of coating the inside

of the box with resin, i might do that.

so 7.5-8 cubic feet, 32hz, and the dimensions i have to work with in the back of my explorer are 44.5" wide, 25" tall, 22" deep. Maybe 30" tall if it makes a huge difference.

i apologize for this, i know how annoying these "please build me a box!!!" posts are, but i need help....

thanks!

Edited January 30, 2010 by Frostedflakejake

[porker_2003 0]

[ baffel(s) 32'' x 22' '] [ bottom 32'' x 22'' ] [ sides 20.5'' x 23.5'' ] [ front/back 32'' x 23.5'' ] \gross airspace 8.5 cu ft / port volume 1.18 cu ft /port area range 88-117 in/ physical port length 18 in / port area 110 in/ net airspace 7.32/tuning freq. 32.15 hz

[Frostedflakejake 148]

thanks!

but why does the baffle and bottom go wider than the sides?

"baffel(s) 32'' x 22' '] [ bottom 32'' x 22'' ] [ sides 20.5'' x 23.5'' ]"

shouldn't the sides be 22"X23.5" then to make it so the baffles and bottom don't overextend past the side boards?

and "physical port length 18"" means that the port goes 18" into the box?? if so then where do i start it from the edge?

i apologize but i don't know the language well enough to fully understand

[altoncustomtech 773]

If you notice, they're exactly 1.5" longer. That takes in account of the 3/4" on each end overlap you have to have to attach the sides to the top and bottom, that's to keep the air space inside the exact dimensions.

Edited January 30, 2010 by Alton

[Frostedflakejake 148]

oh!!! dur. thanks alton. Any advice on the whole port thing? the 18" means it goes 18" into the box right? so then how far from the side piece do i make the port?

[altoncustomtech 773]

It looks like Jon recommended 110in^2 of port area. If you divide the port height (20.5") by 110 it will give you the port width, approximately 5.365" or 5 3/8". Unless Jon had something else in mind.

[Frostedflakejake 148]

okay =] thanks for all your help.

so i just make the port side board 5 3/8" shorter, right? so it doesn't connect to the side. and then i connect another board to that going 18"into the box right? Just double checking =]

[altoncustomtech 773]

Yes, that is correct. Don't worry, once you've been in the game awhile this will all come a lot easier. A person has to start and learn somewhere, and by the look of your setup so far you're way ahead of the game compared to where most of us (especially me) started. Good luck with the build, make sure you take pictures and start a build log too!

[Frostedflakejake 148]

yeah this is my third system.

pioneer championship series 12" in sealed boxes

two mtx tr55's 12's in mtx ported box < actually pretty good

both powered by a Crunch p1100.2 < definitely not a powerhouse, but it did take quite the beating physically and electronically.

but yes, this is by far my first "real" set up.

thanks alton and jon for your help =]

and yeah a build log is a must!!

[Mac N Cheese 90]

if you do plan on resining the inside of the box then here are the supplies i would get. Gallon of fiberglass resin (it comes with the hardening solution), gloves, facemask or just be in a open area, a bowl but remember it's going to get ruined. Let me know if you have any questions about resining.

[Frostedflakejake 148]

thanks mac n' cheese. i have quite a bit of experience with resin so no worries. but yeah it's definitely being done in the garage, its too damn cold here in michigan. I'll let you know if anything comes up. I appreciate it!

[Frostedflakejake 148]

by the way mac n' cheese, i see that your BTL is near the port side of the box where in most of the ones i've seen, the sub is on the other side of the port. Any special reason for this?

[Mac N Cheese 90]

by the way mac n' cheese, i see that your BTL is near the port side of the box where in most of the ones i've seen, the sub is on the other side of the port. Any special reason for this?

Yeah after making the box i found out that you want the sub as far away from the port as possible but i just made mine in the center..no specific reason besides looks