How do you calculat port area??

[99xtremedime]

Helping a friend get a box together for his silverado and its not exactly something i can type into torres. The box after sub displacement is 1.01 cubic feet and im looking at using a 4" areo port at 29" long for roughly a 33hz tuning and i know that the port @ 4" diameter, 29" long is 364.24 sq in of port. But i need the port to be be 5" external and the rest inside the box. Does that effect anything? And how would i calculate the port area per foot?

[Nivram]

364.24sq in is alot of port area for a 4in areo port

[Nivram]

smaller the areo port diameter, the lower itl sound with less port length bigger the areo port diameter the longer you will have to make it for the same low tune.

[SGT_76]

I may be wrong but I thought to calculate port area of an aero port, you just find the area of the opening...4" aero = 12.56" port area? Using this number for your "port area per foot"?

But like I said I could be wrong.

[Nivram]

^correct

[Nivram]

360 sqin of port would mean you have 30in tall 12in wide wayyy to large for a 1 cube box

[mikeg321]

First off, a 4" aero has an area of 12.56 sq. in.

Your port volume is 364.42 cu. in.

Now calculate your box volume in cubic inches. 1 cu. ft.=1728 cu. in.

Assuming your doing a single baffle we subtract 5.75" from your port length (its gonna be outside the box so it won't effect the box volume). Now we adjust your port volume 12.56x23.25=292.16 cu. in.

Now subtract port volume from box volume 1728-292.16=1435.84

So your box after port displacement is 1435.84 cu. in.

Now we have to turn that number to cu. ft to calculate port area per cu. ft. 1435.84÷1728=.83 cu. ft.

Finally divide port area by cu. ft. 12.56÷.83=15.13

So you have 15.13 sq. in. Of port per cu. ft.

[Nivram]

you will be fine with an external port

if you need the extra length for the tune to be right.

[99xtremedime]

Thanks for the help man!! So with that setup do you think that it would do pretty good with a sundown sa-10 on roughly 1000-1100 WRMS of power? And one of the things that I was most worried about was having the port be partially external will it effect the tuning at all? Say I run into clearance issues with the magnet and have to move it 2" or so. Would the tuning still be 33hz? I mean, I know that it would change slightly because the internal volume would increase slightly but were only talking a fraction right?

First off, a 4" aero has an area of 12.56 sq. in.

Your port volume is 364.42 cu. in.

Now calculate your box volume in cubic inches. 1 cu. ft.=1728 cu. in.

Assuming your doing a single baffle we subtract 5.75" from your port length (its gonna be outside the box so it won't effect the box volume). Now we adjust your port volume 12.56x23.25=292.16 cu. in.

Now subtract port volume from box volume 1728-292.16=1435.84

So your box after port displacement is 1435.84 cu. in.

Now we have to turn that number to cu. ft to calculate port area per cu. ft. 1435.84÷1728=.83 cu. ft.

Finally divide port area by cu. ft. 12.56÷.83=15.13

So you have 15.13 sq. in. Of port per cu. ft.

[mikeg321]

I'm really not familiar with sundown subs so I don't know what kinda enclosure/power they like. I'm pretty sure Torres calculator has a box for external port so you'd just enter your port length then enter the external length. If your move the port out of the box it will lower the tuning a little but I doubt it would make an audible difference.