4 18 BTL box

[tejcurrent 13]

I've been searching google for a long time now, trying to find the actual formula. I have always used an online calculator when building my boxes, and ended up just building where I thought looked good.

I was using this calculator here: http://www.carstereo.com/help/Articles.cfm?id=31

because I am wanting to build a new enclosure for my yukon, but I keep getting different figures depending on if the width of the port is larger, or the height.

I want to build a box with 20ft after displacement so each btl will have its minimum 5ft. I was going to see how long I needed to make the slot port if I just stretched it across the bottom of the box.

The box external dimensions are 48wx25hx39d, with double thick faceplate. This gives the port about 5" from the rear doors. I was going to make the port 46.5wx6hx12d. Going from this I figure:

the box will be just shy of 23ft minus sub displacement(1ft) and port(2ft)(estimates of course)

giving me the the 20ft I need, while having the port a little small. I figure once it gets up to a certain volume you wont really be hearing port noise much anyway though

I'm getting that the box will be tuned a little over 35hz, but since it's so close to the rear door I figured it would probably be lowered a bit. am I right in this?

I would appreciate any help, but if someone could give me the equations so that I could do it myself too that would be great. I used to have them, but I just moved and can't find any of my notes

Thanks.

Edited June 10, 2007 by tejcurrent

[Acidburn 10]

http://mobile.jlaudio.com/support_pages.php?page_id=165

[tejcurrent 13]

Acid burn, I love you. Funny, as soon as I asked I went back to my old house and found my copy of car stereo cook book.

So at 12" long I'm around 33-34hz after correction. Plus with the ports so close to the door, I'm probably a little lower, correct? I wish I could go bigger, but I guess that'll come when I get a suburban. Then I'll want 6 18s

Thanks for the quick reply.

[theabunai 3]

suburban has more cargo room then the yukon ?

Damn i haven't looked in the suburban in a long time

Edited June 11, 2007 by theabunai

[tejcurrent 13]

I have a 99, i believe the suburban has 12-16" more length wise. That may or may not give room for six, but it would def. give room for a much better box/set for the 4 18s, and more room in the middle too. The rear windows go all the way down!