flared ports confusion

Okay, so the paper that i got with my 3" flared ports has a formula on it and i run the formula, and it comes up with a different number than what the psp calculator gives me. Which should i trust? andyone have a formula, not another calculator for aero ports? I have uploaded a picture of my paper with the formula on it. Do not pay attention to the numbers ive written, those were for a different box. If u need any more specs of anything, lemme know. BTW, the subs are treo ssi 12.22s. they will be going in a box approx 2.86 gross volume. I am looking to tune to 28hz.Disturbin' Tha Peace

Okay so i figured it out finally. There is a subtraction sign between the division part and the end of the equation. Thought it was a photocopy artifact lol. So, this leads me to my next question however. Is a 3" port tuned to 28 hz big enough for a treo ssi? The net volume is 2.65 ft^3. I am also wondering when i go to calculate my net volume, I have compensated for the sub but now how do i compensate for the volume of the port in the box? If the port is already set length, when i compensate for the volume of it, wont it change my tuning frequency, thus making change the length again, and then a paradox forms? LOL i'm a lil confused on that part.Disturbin' Tha Peace

As long as you are within 10% of your calculated volume the change in tuning frequency is insignificant.... unless you are building an all-out SPL comp enclosure, but you are not doing that.  As far as a 3" port being too small, that depends on a lot of things.  In general if you are mounting the enclosure in a trunk or other space not in the passenger cabin, you won't know the difference.  If the enclosure in in the passenger cabin, you might hear the port making noise when you push to extreme volumes.  The only way to know is to calculate the port velocity, or to model your system in a program like WinISD.Support the12volt.com