Help with calculation?! what is my box tuned to?

[jasonjs 10+ year member]

Width 35 Height 15 Depth 24 its 1inch mdf and has a round port 8" and depth is 20

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[Kadori 10+ year member]

according to the12volt.com your box is tuned to ~30hz

 

[lest]

I have a 7cubic feet box and want to tune it to 32h I have two four by four inch square Ports how long should they be to get that tunning? The box is sealed,but I want to get louder.. Thank you.

 

[Kadori 10+ year member]

about 9 inches, though i would suggest getting more ports than that