box/ port design help

[Dwayne B. Stegent Jr.]

Dual 12" L7's. Box dims are 40w x 20d x 15h. My first ported box build. Need help with the port dims. I'm thinking @ 35hz. Unless there's a better tune for these subs? The amp is kickers ZXS1500.1 if that matters. Any advise is appreciated. Thanks.

[ROLEXrifleman]

slot port 4" wide 13.5" high 15.25 long

[ROLEXrifleman]

use as a guide:

http://reaudio.com/box.php

along with the Torres box calculator

[Dwayne B. Stegent Jr.]

Awesome ROLEX, Thanks. Question tho. Would a larger port area, say 75 sq in, instead of 54 sq in, adversely affect anything besides the length of the port?

[ROLEXrifleman]

Many on here debate what the magic number is when it comes to box square footage and port area. I try and stay between 12-15 square inches per foot. the determining factor will be how much space you have available for the build and how much air space your port will take up. If you go bigger on the port area i will generly cause the tuning freq to be higher.

the specs I gave you above came out to a 32hz tuning.

If you made the port 5" wide and 14.25 incjes long you end up with 67.5 square inches of port area (14.14 square inches per foot) and a tunning frequency of 36hz. In that box the subs have about 2.25 cubic feet each.

Not sure what those subs like but it sounds about right.

hope that makes sense

[Dwayne B. Stegent Jr.]

Makes sence. Thanks again.

[Dwayne B. Stegent Jr.]

Is there a real audible difference between a 32hz tune and a 36hz tune?

[Joe X]

Sure there is.

[Dwayne B. Stegent Jr.]

ok....im new to ported boxes. Whats the difference?

[Joe X]

Frequencies below tuning will roll off fast so if you listen to very low tuned music like rap you will miss much of the low end tuning higher, sure enough the exact effect of tuning depends on the sub itself and the box size as well. 1-2Hz tuning difference is difficult to tell apart but more than that is usually audible.