Fi BL 18" Port Design

[kschutz 0]

I have a 2003 Chevrolet Tahoe and I am going to put a Fi BL 18" in it.

It will be powered with a Rockford Fosgate T10001bd amp and a Kinetik battery.

Just ordered it yesterday

I have a general idea of the specs on my box in order to fit the 5-10 cubic feet.

It will be about 9 cubes by the time everything is displaced.

The only problem since I am new to car audio and this is my first system is what are the dimensions of the port?

The box will be W 45" x H 20" x D 20" with 3/4" MDF.

I want to tune the box to 32Hz.

Any help will be appreciated.

-Kasey

Edited December 21, 2008 by thehoe92

[Duran 387]

144 sq. in. of port

[kschutz 0]

I'm not one to just take advice and not question how or why...

so could you tell me how you got that number in case I want to change something?

[Duran 387]

I'm not one to just take advice and not question how or why...

so could you tell me how you got that number in case I want to change something?

I'm glad you asked 18" subwoofers need 14-16 square inches of port per cubic foot. 14x9=126 16x9=144. You need anywhere between 126 and 144 square inches of port.

[danieln_88 0]

a general rule of thumb is 12-16 sqin. port for every cube

[kschutz 0]

thanks for all the help guys

[kschutz 0]

oh yeah I forgot one last question...

if I make it 144 sq inches then would tuning it be just as easy as turning the knob on my amplifier to the desired frequency?

[Duran 387]

thanks for all the help guys

No problem Be sure to make a build log for us though!

[Duran 387]

oh yeah I forgot one last question...

if I make it 144 sq inches then would tuning it be just as easy as turning the knob on my amplifier to the desired frequency?

No. Tuning is attained by the port length.

[kschutz 0]

I shall...

so to attain 32Hz the port length should be?

sorry I have so many questions.

a few years from now I will look back and see how much of an idiot I am for not knowing these seemingly simple questions.

[danieln_88 0]

what i got was 8"wide x 18.5" tall.... that will give you about 148 sq.in. port and tuned to 32.... length would be 33"

[Duran 387]

I shall...

so to attain 32Hz the port length should be?

sorry I have so many questions.

a few years from now I will look back and see how much of an idiot I am for not knowing these seemingly simple questions.

Believe me, that is not a dumb question. We get a lot of "What sub will hit harder? I want to be heard from 10 miles away!"

[kschutz 0]

haha that is true.

well anyways thanks for all the help

[danieln_88 0]

I shall...

so to attain 32Hz the port length should be?

sorry I have so many questions.

a few years from now I will look back and see how much of an idiot I am for not knowing these seemingly simple questions.

Believe me, that is not a dumb question. We get a lot of "What sub will hit harder? I want to be heard from 10 miles away!"

x2.... designing took the longest to learn for me.... especially the port....

[kschutz 0]

what i got was 8"wide x 18.5" tall.... that will give you about 148 sq.in. port and tuned to 32.... length would be 33"

I don't see how that is achievable in the box I am designing.

if the width is 8" and then length is 33" thats 41" witch is over my width.

is there a better way you can explain it?

or even better draw it?

[Duran 387]

what i got was 8"wide x 18.5" tall.... that will give you about 148 sq.in. port and tuned to 32.... length would be 33"

I did not get 32 Hz. with those numbers. I got 40 Hz. tuning.

[danieln_88 0]

hang on..... i think i eff up for you.... i think i did 9 cuft. before displacements...

[Duran 387]

hang on..... i think i eff up for you.... i think i did 9 cuft. before displacements...

Mine comes out to 5.7 cubes after displacement.

[RobClay 20]

what options did you choose on the bl?

[danieln_88 0]

hang on..... i think i eff up for you.... i think i did 9 cuft. before displacements...

Mine comes out to 5.7 cubes after displacement.

how did you come up with 5.7 cuft. after displacements??

[Duran 387]

hang on..... i think i eff up for you.... i think i did 9 cuft. before displacements...

Mine comes out to 5.7 cubes after displacement.

how did you come up with 5.7 cuft. after displacements??

I dunno I just did. It sounds a little weird to me too.

[danieln_88 0]

well... when i was putting numbers in... i thought that the port width sounded a little to big for me.... but... idk....

but when i think about it... i can see it displacing alot....

Edited December 21, 2008 by danieln_88

[kschutz 0]

what options did you choose on the bl?

I got the 18" dual 2 ohm, cooling, and daily.

I didn't get the flatwind because I read on this forum somewhere that it is preferably used for SPL application.

[danieln_88 0]

hang on..... i think i eff up for you.... i think i did 9 cuft. before displacements...

Mine comes out to 5.7 cubes after displacement.

how did you come up with 5.7 cuft. after displacements??

I dunno I just did. It sounds a little weird to me too.

yeah i think thats what i did.... 22.25" sound better??

[kschutz 0]

ok so what I have gathered is:

A.) is 8"

B.) is ?

and

C.) is now 22.25"

I am just trying to visually see it...