Help With 18 BTL Box

[bdawg8527 0]

Ok, well i had no idea about tuning or anything when i made my first box. its 9.5 cubic ft with 90 in of port area, and i ran the port length till about the back of the box. ( pics soon). what i was wondering is can anyone provide me with the actual formula for calculating my port length. ( so i can just plug in hz volume and port area? ive got some calculators but like to see everything out. here is what im trying to accomplish by just cutting the box.

34 hz tuning

7.5 cubic ft

90in squared of port area

if i my box in a 01 grand am running from my trunk to my back seat, with the btl right in the back seat and the port under it. if i put the port in the trunk would it make it sound worse?

[bigrank916 72]

What are the dimensions of the port? How wide is it? How long are the port walls?

You should have come here first so we could have helped you design it properly.

[bdawg8527 0]

port is 4in by 23.5 in and it goes back id say like 40in lol. box is 57 in long

[bigrank916 72]

port is 4in by 23.5 in and it goes back id say like 40in lol. box is 57 in long

Ok. You have 94in2 of port area. The port walls that arent shared as the outside of the enclosure should be measured. Ie if your port bends to the right, then measure the right side of the port walls. This meaning the two boards on the inside of the enclosure that make the L.

I have 57"W x 25"H x ? What is your depth so we can find exactly what the gross volume is?

[bdawg8527 0]

my bad its only 22.5 in wide box dimensions are as follows

57in long 24in wide and 15in tall

all made with .75 mdf

and the port is in the front right under the box going back the length of the box. port dimesions are 4in by 22.5in

[bigrank916 72]

my bad its only 22.5 in wide box dimensions are as follows

57in long 24in wide and 15in tall

all made with .75 mdf

and the port is in the front right under the box going back the length of the box. port dimesions are 4in by 22.5in

If thats the case, you dont have enough port area for this size enclosure. At the minimum you would want 108in2 for a 9ft3 enclosure. A general rule of thumb is 12-16sqin of port area per cubic foot of volume.

Maybe you can cut the face down and make the port wider? This will change the tuning and as well as the port boards. Definitely should have thought this out a little more before you put this together.

[bdawg8527 0]

i plan on cutting it at 42in and adding the back there. so itl go from 57 in to 42, which should make it 7.5 cubic ft. and the percice is 42.66 in, then making my port 20.14 in log should give me 34 hz right?