New Fi Bl 15" box plans

[Julian 641]

alright, so i have a FI Bl 15" with, cooling,daily, universal d1. I am planning on building a new box because my current box only takes up 1/2 of my trunk which is in fact bad. Due to the trunk and how it is made there are two metal bars coming across the length of my trunk, and it makes my sub box aprox. 1 foot away from my trunk lid, which i think lessens the well initial BOOM, when i had my MTX JH55's in they sounded much louder when they were pushed back so i thought well "why the hell not build my own box" here are the specifications, i even made a pretty picture for you guys. ports from eD.

(made in Google Sketchup!)

Ideas, comments, suggestions?

(some insight from Blue Fury would be nice )

[NB50 206]

Tuning seems really high.

[Julian 641]

wouldn't it be tuned to about 30 hz?

yes it would be tuned at 30hz

Edited June 9, 2009 by Julian

[sadistic 13]

Tuning seems really high.

wouldn't it be tuned to about 30 hz?

yes it would be tuned at 30hz

hi bromo i wondered over here for a wile

yes it is tuned to high. you will need 2 ports 12 inches long that are 4 inch inside diameter to be 30 hz i think you are using single wall material "3/4 inch mdf" for 5 cuft total right ? if doing the box right you have to split it in two sections of equal portions like 2.5 cuft. you can't just can throw two ports in five cubes it will have a high tune and be very short ports. i will post a link to a port formula and if you need help crunching the numbers i will help ya. just say some thing if you would like the math.

[sadistic 13]

http://www.ecalc.com/calculator/scientific/

use this calculator at link above

square root key look like a check with a x inside

powers of ten key looks like a y to the power of x

av =10

lv=30

vb=864

do the this part first av(1.84x10to the power of key looks like y sub x when the calculator does the y to the power of x key it will put some thing that looks like a up side down carrot.

Then write the answer to all of the above down

Next do vb(lv+.823then hit the square root key put in av then write the answer down

Take the first answer and divided buy the second one

Then take and put in to the calculator .159 square root of the answer of the two this should equal 40.63716007346 hertz for the fb

Just remember you can plug any thing you want into av or lv or vb that the plug part

Av =a 2 inch by 10 inch wxh or area of vent

Lv = length of vent

Vb = volume of box

just try to keep the area of the vent less then a 9 :1 just divide like a 10 by 5 inch port in to this 5/5 and how many section of ten you get and 10 /10 and how many section of 5 you get this would equal 1x10inch and one 1x5 inch the 1x5 would pass but the 10x1 would not it to big

here are some other formulas

pie times radius squared

radius is half of a circle and this trans forms a round to a square vent real quickly

square root of

[sadistic 13]

use the formula/ info at this link in conjunction with the info above

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

[NB50 206]

wouldn't it be tuned to about 30 hz?

yes it would be tuned at 30hz

I got it figured out after all displacements to be ~4.38ft^3 @ 52Hz

Tuning seems really high.

hi bromo i wondered over here for a wile

[Julian 641]

i used http://www.the12volt.com/caraudio/boxcalcs.asp to calculate the port calcs, using the formula ((14630000*(D/2)*(D/2))/((Fb*Fb*Vb*1728)-(1463*(D/2)))) i get a port length of 5.43591 inches

[NB50 206]

That would work if you were going to use one port but you said you want two. For two of them to tune to 30hz and keep the same dimensions, they are going to have to be 15in long each. So that would put you at 4.15ft^3 @ 30hz after all displacements.