enclosure for 18" questions math and calculation help

[96i30 10+ year member]

allright so ive stooped real low and bought an audiobahn 18" ultra excursion subwoofer model number AW1805Q, i know ill get some hate for it but i want to try it out...so i have a ported box that id like to try and use for this sub it took me forever to make it and id hate to see it go to waste. i would like to try and modify it, it used to have 2 kicker 12's in it i would just replace the board they sat in. i would like to know a few things that i cant figure out on my own...

1. attached below is a diagram of the box..from the outside of the wood so excluding the 3/4 mdf the sub box measurements are 31.5x28.5x14 1/8... the port measures 3 7/8 wide x 21 deep x 12 5/8 high all air no wood in the port measurements , just out of curiousity what was this tuned to? im not sure what the displacement is on 2 kicker 12L7's

2. if i were to take the same size box and put the 18" sub which displaces .148 cuft how much space would i be using and what would the new tuning be if i didnt modify the box at all?im looking for around 31-35 hz... below are the box specs audiobahn reccomends for this sub which is on the far right of the table. thanks alot guys!

http://www.audiobahn.com/Audiobahn06/images/tech/2004/boxParams/AW05Q_box_specs.pdf

Click to read more...

 

[Chevyaudio 5,000+ posts]

From that very very rough drawing I got...

~5 cubes

~59.375 Sq inches of port

21 inches of port length

That being said...that box would be tuned right around 34 Hz.

Edit...

No displacements were acouted for above....with that 18 Displacing around 0.2 cubes, it would be tuned to 34.8 Hz.

 

[96i30 10+ year member]

From that very very rough drawing I got...
~5 cubes

~59.375 Sq inches of port

21 inches of port length

That being said...that box would be tuned right around 34 Hz.

Edit...

No displacements were acouted for above....with that 18 Displacing around 0.2 cubes, it would be tuned to 34.8 Hz.

how did you get 59.375 of port? are you taking 3.875" wide X 12.625" height?

i got 48.921 when i multiplied them together am i doing something wrong?

 

[mazdakid 5,000+ posts]

he did 12.5 x 4.75

 

[96i30 10+ year member]

oh well the proper mesasurements are 3.875" wide X 12.625" with i guess 48.921sq inches of port with 21 inch length what would that make the tuneing be? and then if i put the 18" in there what would it change to?

 

[Chevyaudio 5,000+ posts]

How is it 3.875 wide when your drawing states that its 4.75???? With the NEW diminsions that you have givin Its tuned to 31 Hz. Thats without displacements of the sub(s) with it would be around 32

 

[96i30 10+ year member]

i think i included the wood in the old measurements or something...how do you think the 18 would sound in this box? and in a ported box, does it matter where the sub is placed in relation to where the port? should the sub not be placed close to the port or does it not matter?

 

[Chevyaudio 5,000+ posts]

well considering its an audiobahn I'll reserve what I really think will happen. But that box seems a tad on the small side for most 18s that I've messed around with. Hell I have a single 15 box sitting in my apartment thats 5.1 Cubes @ 25 Hz. So take that for what its worth.

 

[Fate710 10+ year member]

try it and see man. but like chevy said don't count on much. for 1 its an audiobling and for 2 the box is a wee bit small. hell my last 18" setup was in a 7.25 @ 37Hz. That was a stupid loud setup. If you haven't cut out any holes yet and still have the box sealed up I would try and sell it to someone needing a nice box for a 15" sub setup.

 

[96i30 10+ year member]

i cant make the box much bigger then what it is other people that have had this box told me to tune lower then 35 because it lacked on the low side in a 35 hz box and that a slightly bigger box would be beneficial, this is comin from a guy that had it in the box audiobahn reccomends to spl specs which is somewhere in the 4 cu ft range, this would be in about 5 cu ft so hopefully it wont be too bad...i know audiobahn isnt looked upon as one of the best here but hopefully it will sound decent

 

[96i30 10+ year member]

bump does it matter where the sub is placed in the box in comparison with where the port is? like should the sub be placed on the opposite end as far away from the port as possible or could you put the sub right next to the port and it sound the same

 

[Trixter 10+ year member]

bump does it matter where the sub is placed in the box in comparison with where the port is? like should the sub be placed on the opposite end as far away from the port as possible or could you put the sub right next to the port and it sound the same

ideally, if on the same sied as the port, farther to the opposite side of the port.