Help with final box design!

[Carroot1]

i have a question. im designing my box with 2 common walls and i dont know how long i should make the port wall. Torres calc says the physical length is 20.75in is the per side or just all together it also says the port bends.

[SwaggerWagon]

Well, looking at what it told me, I'm not really sure. What did you put in the "port length" box? I did the manual calculations before I put everything in Torres' calc, so I'm making mine 32 inches long.

And when you say two common walls, will you have a port on each side? Mine is going to be in center of the box

[Carroot1]

mine is in the center

[SwaggerWagon]

Alright. It means it's going to have to split to the left and right when it gets to the back wall. And go by what is in the "port length" box if I'm not mistaken. That's how I calculated it to be. And what you do is;

Take the width of the port from the "Port Demensions" "width" box, and divide it in half.

Now, subtract that from the over all length of the port (the "port dimensions" "length" box). Now make the port start at the front of the box, and go back so that it is as long as the difference you just calculated.

Now, take this length and subtract it from the overall length, and divide by two.

Starting in the center where the port ends, measure to the left and right for the most recently calculated distance.

It's long but that's how I did it to make sure the port will be the proper length.

[SwaggerWagon]

I can write up a formula for it if you want, and u can just plug in the numbers. This is, of course, assuming I'm right about everything here.

[Carroot1]

the physical port length is how long the wood on the port is.

[SwaggerWagon]

Ahh makes sense! Okay, so if you complete the steps I posted above, you should get what I'm going to call initial port length, and it should be equal to the physical port length.

In other words, physical length is length before it bends

[SwaggerWagon]

Alright so I PM'd Torres and he had some great answers:

Torres:

physical port length isn't necessarily the length before it bends. that would only be part of the length. if a port is 4" wide by 10" tall and 20" long and doesn't bend, the physical port length would be 19.25". the missing .75" comes from the baffle or wall of the box that when added together gets you 20" long. now...when a port bends, the bend in the port makes it seem effectively longer which is why the physical port length is shorter. so using the same port, if it bent then the physical port length would be 15.25". you have 20" minus .75" for the baffle/wall, minus 4" due to the bend in the port, which gets you 15.25". here's a picture to kinda help show what i mean if you made the 'physical port' as long as the effective port (which is the port entered in the port length box).

so as you can see, if the port bends and it is still made the desired length then the port will effectively be longer than it should be, lowering tuning and taking up more volume in the box.

as for your box, the pic you posted looks good

and since you're using 2 common port walls in the middle, you're right that the width gets divided in half after the bend. so in the middle it'll be 4.8" then when it splits it'll go down to 2.4" and continue along the rest of the port.

hope i helped answer all your questions

[SwaggerWagon]

Here is the image Torres was talking about with regards to port bend