Question on "extending" square ports

[bumpinTL364]

Okay, so some of you may know I want to build a box for a pair of 10s with a square port in the center (given that gives me enough port area). We all know that you can extend a slot port on either side to achieve the desired port length like so:

However, I was wondering if it works to do essentially the same thing but with a square port by extending it on all four sides, like so:

NOTE: please note that these are just examples, I do understand that for the slot port you'd take half the port width and keep each "extension" that length away from the rear wall in order to keep the appropriate port volume. How would one figure out how far to keep the "extensions" on a square port from the wall, given that this idea actually works out mathematically?

[Triticum Agricolam]

The way you have it drawn won't work. Your port needs to maintain a consistent cross sectional area. Once you reach the end of your box shaped tube your cross sectional area is increasing. To do what you want to do you need to do something like this:

[bumpinTL364]

ah, so what you're saying is that i'd have to essentially split the volume of the square in half and extend the port using those measurements? makes a lot more sense actually, I just thought that if I maintained port area with the surrounding square extensions it could work…although in retrospect, I could see there being some sort of issues with how air moves over the top and bottom of said square, possibly causing port noise or high inefficiency...

[jk13]

Your port needs to maintain a consistent cross sectional area.

^^^This.

if I maintained port area with the surrounding square extensions it could work

Maintaining one dimension of the port is not enough, the cross section width x height needs to be the same while adding length like mentioned above. You are only maintaining the width using the back wall and the square in your scenario, not the height.

[Chance_P]

I would think you could do what Trig A posted, but with a vertical extension also, you would just have to make the 4 smaller ports have the same total port area as the original port. Is this correct? In my head it makes sense, but thats A LOT of port area for the air to move across. (Port area as in the inner walls of port)

[bumpinTL364]

^^^ that also makes sense, but I would worry about port noise of the vertically-oriented ports loading awkwardly and/or inefficiently