Im pretty sure Ive seen this before. wondering how the port length is calculated. say the port opening is 3.75x13, Id assume when it splits Id make each continuance of the port 1.875x13. do I measure the length of the first part before it splits, and add to it the length of the part after the split to get the overall length.

do I calculate the length as if I were running 2 1.875x13 ports, or a single 3.75x13 port. with the box volume and tuning I was using, they were very similar, 29.6 for one and 28.92 for the other scenario, so either one would end up close enough, but Id like the know the correct way. if either of these are correct.

You would measure the total length of the port by including both the single and double width lengths.

alright, and just so am 100% sure I get what you mean, I include the lengths of the wide part plus the length of only one narrow part right? not main part plus left side narrow part plus right side narrow part.

Right, just wide part plus one narrow part.

gracias.

I personally wouldn't separate them and if I did I wouldn't have them join each other in the middle. Not a good idea. Just run it either on one side of the box or treat it completely independently as two boxes and include a divider down the middle of the port

alright, I originally had drawn it out with a port at each end, but figured it see about doing it this way because I like the looks of the double flared port between 2 subs. could always still flare it like in the pic even if I do have a straight board in the middle.

alright, I originally had drawn it out with a port at each end, but figured it see about doing it this way because I like the looks of the double flared port between 2 subs. could always still flare it like in the pic even if I do have a straight board in the middle.

Yes, I would also recommend using the two ports instead of joining them. I have debated others about the effectiveness of using this design. I personally have been told many times that it is not a proper design and you will get better performance by simply using separate ports. You could always add a piece in the middle like you said.