View Full Version : Building custom FG box question on sound w/ cf?

03-16-2010, 04:13 PM
OK, so I am building a custom fiberglass sub box for my evo x, and will be putting it in the stock location of the factory sub box. Here is an example of an aftermarket one that is about 1.0 cf and mine will be a little larger, probably about 1.25 cubic feet.



The reason I am making this post is not because I dont know how i want to do the box, but because I am concerned about the sound of it.

I am a fan of boomy bass.

I have picked the following components

12" JL W6 subwoofer
500w RMS amplifier (alpine PDX or JL amp)
Customer fiber glass box

I have a lot of friends who are saying I wont get good sound from a sealed box no matter how big it is. Can someone who has more experience w/ the different types of boxes/sound tell me what I can expect? I always thought the sub controlled the sound, and if you got a good sub, as long as you followed the Manufacturers specs it will sound good regardless of if you went sealed/ported/vented/bandpass.

can anyone confirm what I would be in store with by going w/ a sealed 1.25 cf box using the components above?

will I loose boomy?

03-16-2010, 05:02 PM
it will be half as loud but will sound great.

03-16-2010, 05:10 PM
If you're used to ported, sealed will not sound boomy. I would have made a test sealed box before I spent the money on a FB box without knowing how it is going to sound.

James Bang
03-16-2010, 05:16 PM
whip up a quick sealed mdf box to test.

03-16-2010, 05:20 PM
would it be worth building one of these into the box?

2" x 2.5" Port Tube Subwoofer Sub Woofer Speaker Box


does it have to be a certain way, or can I just put it anywhere and be good?

James Bang
03-16-2010, 05:24 PM

03-16-2010, 05:28 PM
its a port, a small one. could I add that to a 1.25 CF box, and get boomy from it, or is that a pointless idea?

12 W6 requirements

Sealed Enclosure Range: 0.50-1.00 cu.ft. (14.0-28.0 liters) Ported
Enclosure Range: 0.75-1.25 cu.ft. (21.2-35.5 liters)

so if I do a 1.25 cu.ft box, and add that port, would I be in good shape?

James Bang
03-16-2010, 05:32 PM
Basic Car Audio Electronics (http://www.bcae1.com/)

03-16-2010, 05:39 PM
it says if I buy the port, and use a 1.25 Cu ft box, by having it at that length/width it will tune the box to 35hz. I would figure if I did that, I now have a ported box, and would regain my boom and be happy?

I tried that site you linked, its 135 pages long, and i couldnt find anything specific to the question above.

James Bang
03-16-2010, 05:59 PM
Subwoofer Enclosure Calculators, Fraction to Decimal, Parallel, Series, Port Length and Volume Calculators (http://www.the12volt.com/caraudio/boxcalcs.asp#por)

Check the round port length calculator.

a 1.25cuft box with a 2" port with 2.5" length gives you ~41hz tuning.

03-21-2010, 08:39 PM
OK, so I built my box, and after measuring w/ peanuts, I was able to verify that my box is about 1.65 cu ft.

Right now it is a sealed box. I did buy a port it is a 3.75" x 7 inch port. I am debating if I should keep this a sealed box, and if 1.65 is good for a sealed box with a 12" W6v2 w/ a JL audio Slash v2 amp. This will be in the back of an evo w/ a very small trunk.

Should I keep the box sealed @ 1.65 cu ft, or should I add the port in at 1.65 cu ft?

what would the difference in sound be between the two?