porting a box

[phil9922 10+ year member]

when i first got into car audio, i bought my subs and the standard sealed box they had for sale at the store. now that i know more about car audio, i realized the box is 1.35 cu ft and the subs are recommended for a .85 cu ft sealed box. the specs for the subs in a ported box is 1.25 cu ft, so i figure after the displacement of the subs the box is the perfect size if i can port it. can i just go buy ports and start cuttin, or does it have to be specially tuned? if it has to be tuned, is there a way to do it w/o special equipment?

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[LoneRanger 10+ year member]

when i first got into car audio, i bought my subs and the standard sealed box they had for sale at the store. now that i know more about car audio, i realized the box is 1.35 cu ft and the subs are recommended for a .85 cu ft sealed box. the specs for the subs in a ported box is 1.25 cu ft, so i figure after the displacement of the subs the box is the perfect size if i can port it. can i just go buy ports and start cuttin, or does it have to be specially tuned? if it has to be tuned, is there a way to do it w/o special equipment?

http://www.eatel.net/~amptech/elecdisc/spboxnew2.htm

Oh...and I'm pretty sure that it means 1.25 PER SUB. You're going to need a 2.5 cubic foot box (after displacement of course) to port both of them. Never ever ever ever ever ever just cut a hole in a sealed box and jam a port in there. The only thing you'll succeed in doing is fcking up a perfectly good sealed box you could have sold.

 

[phil9922 10+ year member]

i already have the specs i need from the manual that came with my subs. it says 1.25cu ft per sub, 4in port diameter x 12in port length, tuned at 40hz. how can i tune it to this?

 

[phil9922 10+ year member]

anyone know?

 

[Trixter 10+ year member]

First you need a box that is 1.25cu'...which it sounds like you have. But you need to account for driver and port displacement. The port displacement in a 4" by 12" round port is .09cu'. Add that to you sub displacement and that is how big of a box you will need.

EX: 1.25 + .09 + .1 (est. sub disp.) = 1.44cu' this is want you need you total box size to be.

If your box is 1.25 and cannot be changed then you subtract the sub disp. and ettimate a port disp.

Lets try....

1.25 - .1 (est. sub disp.) - .1 (est.port disp.) = 1.05cu' enclosure. To tune this box to 40Hz and using a 4" port it needs to be 17" L

The sub disp. of .1 may be on the big side but as I said these are just estimates.

If the specs call for 1.25cu" with a 4" port that is 12" long, and you have a 1.25cu' box already, simply put the port in that box. Manufactures account for the displacement when they give you dimensions. And by doing this you can take what I was saying above and toss it out the window because it may just confuse you.

Hope this helps.

 

[LoneRanger 10+ year member]

i already have the specs i need from the manual that came with my subs. it says 1.25cu ft per sub, 4in port diameter x 12in port length, tuned at 40hz. how can i tune it to this?

Like i said before....1.25 per sub = 2.5 cubic feet.

You're going to need a 2.5 cubic foot box after all displacement (about 2.7 before). If you're dead set on a round port, just follow their specs. I personally perfer square or rectangular ones, but it's not like it makes a difference in sound or anything.

If you're one of those DIY guys, I can draw up some easy-to-follow plans for this box for $10. If you'd like me to build the box for you, I could do that for $90 + S&H without carpet or $125 + S&H with carpet.

My suggestion is to pawn your old box off on ebay before you go cutting holes in it and use that money for materials for a new box or as a down-payment on a professionally built one.