Trying to get the right round port length...help?

I'm using a Fi XV3 12' woofer in a 2.5ft3 net ported box....not built yet. Since this driver will be seen I wanted to keep it symmetrical and have a port on either side of it and I want to use 2" ports. I've looked a few different websites and found different results when I plugged these numbers into the equation. It looks to be between 5.59 and 6.8 inches is what I have found per port. Also I'm not sure how to subtract out port volume, again finding different numbers. I can only assume I take the volume of the cylinder and subtract that from the box volume? lastly what is end correction factor, I saw that and have no idea what that is? I'm not using a flared port, just pvc, but I would if I can figure out the math for it.

End correction is normally taken into account, I’d err on the longer side as some calculations allow for it more accurately than others, I would be tempted to use a flared port also due to the reduced width, and even then a pair of 2” ports is probably a little small, I’d expect a pair of 3” flared at least with something with decent excursion like most FI subs have, I use single 2” ports with 6” drivers generally, and two six inch drivers don’t equal a twelve!

And yes for the port volume it’s literally a cylinder and subtract it from total volume

a good guide for a ported enclosure is generally 14-16 sq ins per cubic ft, so for a 2.5 cubic ft box I’d aim for around 38 sq ins, a little less with flared ports as the flare does its bit to increase effective port area and reduce noise

I agree i think 2" maybe be a little small, I've still got to do some figuring on the box. It will be a "modified" wedge. Think of it like a triangle/wedge shape with the top angle cut off with and extended flat top. I've got to see how deep I want the bottom to be, I'm pretty sure I'll be able to accommodate two 3" ports. Do you know what end correction even is? I'll check into the flared ports.

Yes, a port contains a mass of air that resonates at a certain frequency, so some people think air flows out of a port when infact it makes sound effectively like a speakers diaphragm at and around a given frequency

if you imagine a small mushroom cloud type affair at either end of the port as the wedge resonates back and forth, that is effectively what end correction is for

think of a mushroom over the end of the port, that’s why it adds a fraction to the length effectively, it’s a tiny difference, not really worth worrying about, the parameters of the driver being slightly off have a similar amount of influence (frequently more as production differences make more difference)

for a slot ported enclosure using the side of the box as a port wall generally you’d add half the width from the port wall on the inner end as end correction due to the wedge of airs interaction with the side of the enclosure

if you use the physical length of the port as the length it will only ever tune a fraction lower if anything, but it also takes up a fraction of the box space, so it effectively cancels out, it’s less than 1hz if anything

Mushroom clouds and atomic bombs of sound going off in a cylinder....that's what I'm talking about.....LOL

I found this place online called Mobil Info Lab and using two 3" ports the length for each appears to be 11.8" each. I was also looking at Precision Sound Products and they came up with 12.8" for each using their calculator, however they also said to count and extra inch for the porting so I guess that's where that comes into play. I forgot to mention I'm going to tune this to spec of 33hz unless anyone has other recommendations of a better frequency that achieves better results. And since the PSP ones seemed to be pretty cool, I might as well go with the flared one, again I'm open to suggestion.

Go with 12.8”, as I say it won’t make a massive difference and I’d rather it be a fraction longer than shorter

That's what she said...LOL You must be a night owl or work overnight like me....haha Have you ever used them or is one the same as the other?

Does the amount of power effect the port? I was reading on a Steve Meade Designs forum where a guy is using a 12" sub and was going to port it using a 6" port and the amp put out 1200rms to the speaker. Someone recommended he use a 7" port or teo %' ports for that amount of power, any truth to that when jumping up in power?

It was supposed to be two 5" ports