Can't figure out port tuning

[nismos14 5,000+ posts]

I have a box 33 wide by 13 high by 11 deep. The port is 4 inch x 15. Can someone please assist me in figuring out what this port is tuned to? I appreciate any responses.

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[matt_martin87 10+ year member]

I assume it is a 4" round port at a length of 15".

I'm getting approx. 34hz. Someone correct me if I'm wrong.

 

[nismos14 5,000+ posts]

Yep 4 inch round. Ok I kept getting calculations between 30 - 32, but the main issue was some places were saynig that a shorter port like 8.9" would give me the 30 hz tuning.. that threw me for a loop.

 

[nismos14 5,000+ posts]

Anyone else?

 

[evan 10+ year member]

If you guys are using WinISD to check, how do you take the effects of the different speakers out of the equation? I'm not sure how to start a project without having to choose a speaker first, and once I've chosen a speaker it effects the way the numbers are calculated.

 

[iamamp3pimp 5,000+ posts]

no...it effects the graphs...not the numbers

 

[iamamp3pimp 5,000+ posts]

32 HZ before sub displacement.....1.956 cubes @ 31.96 hz

 

[evan 10+ year member]

no...it effects the graphs...not the numbers
32 HZ before sub displacement.....1.956 cubes @ 31.96 hz

So did you find the volume of the box and subtracted the volume of the port to get 1.956? Doesn't the program account for the displacement of the sub also?

 

[iamamp3pimp 5,000+ posts]

yes thats how i got it...the volume of the port and 1/4 inch to account fopr the PVC displacement.

thats assuming its 1/8th thinwall.

 

[rpfuror 10+ year member]

If assume .08 cu/ft displament for the driver and that it is a 4.20 OD port I get net box volume = 1.89 cu/ft @ 22.40Hz

 

[nismos14 5,000+ posts]

The driver is a DLS SP12, magnet is pretty large. http://www.dlsamerica.com/pdf/manrultsub3.pdf thats the manual for it.

So i could potentially be tuned as low as 22.4 hz?! God this is confusing. So With the way its tuned, if I was running a 30hz ssf would that be a bad thing?

 

[Immacomputer 10+ year member]

It's no where near 22hz. I have a net volume of 1.8 cubic feet after port, sub, and wood thickness. The tuning I came to was 32hz.

 

[nismos14 5,000+ posts]

Thats what I get! Maybe he meant 32.4.

 

[rpfuror 10+ year member]

edit... actually, u guys helped me with my math.. I had the wrong number pluged into my equations.

yes = 32.4with 1.8cu/ft net