1. ## Box Help: port sizes

ive decided to get my box custom built for my alpine type r 12". It's going to be in a 2.1ft^3 box (3ft. long +8in. port, 14in high, and 13in wide). I got these specs from an anonymous person. (idk if he wants to be named)

Although, he doesnt know the exact length of the port but does know that it is tuned to 31Hz.
My Question: Would one of those box building computer programs be able to calculate the proper length of the port for it to be correctyl tuned to 31Hz?

Anyone with experience with these programs, could you let me know? Im trying to get this box made ASAP before my speaker comes in next week.

2. ## Re: Box Help: port sizes

just use this formula:
Lv = Av*1.84*10^8/[Vb*1728*(Fb/0.159)^2] - 0.823*sqrt(Av)
where:
Lv= port length
Av= port area
Vb= box volume (in cuft)
Fb= Tuning frequency.

But I think Win ISD can also.

*edit*
is that 2.1 cuft with the port / woofer dispalcement? or with out.
*edit x2*
are those dimensions the dimensions of your port area?

3. ## Re: Box Help: port sizes

if you use 2 2" ports they would need to be 6.93" long to be tuned to 31hz

4. ## Re: Box Help: port sizes

Originally Posted by exteremespl1122
if you use 2 2" ports they would need to be 6.93" long to be tuned to 31hz
That might be correct on some enclosure calculator, but 2" x 7" is not enough port area.

5. ## Re: Box Help: port sizes

Originally Posted by ameduece
That might be correct on some enclosure calculator, but 2" x 7" is not enough port area.
even if you used 2 ports, still not enough.

6. ## Re: Box Help: port sizes

yeah thats true they will need to be rather long with any bigger diamiter than 2"

7. ## Re: Box Help: port sizes

ok noob question port area is that width and height of the port?

8. ## Re: Box Help: port sizes

yes if its a square port H*W. If its a round port its Pi*R^2.

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