factoring in port displacement

[dmz2711]

How do you go about factoring in the displacement if your port into your box volume when finding tuning frequency, if you don't know how long the port is till after you find the tuning frequency....which you can't find till you know your box volume......which you can't find till you know your tuning frequency so you can determine port length and thus volume  LOL. Please help I must be overlooking something stupid. 

[01xtreme]

the way I do it is calculating the port with the entire volume of the box, and then using the length to calculate port displacement. then I subtract that from the box volume, then recalculate using the new box volume. I just basically keep up that process until I get to numbers I like. It might not be the best way, but it works for me.

[Derrick824]

When building a sub box you should already know the net volume needed and the tuning frequency desired.  You then use that info to calculate the port dimensions.  Once you have you port specs then you can figure the port displacement which you'll add to the net volume along with the sub displacement and any other displacement (such as bracing disp.) and that will equal your gross box volume.  Then use the gross box volume to calculate necessary box dimensions and you're done.  Go build your box.

[dmz2711]

so i guess its a PITA considering you are basically going back and forth in a process of elimination to figure out the correct net volume and desired frequency. I just thought there might have been an easier way.  :pinch:

Any good computer programs out their? i know of winisd and bbp, but any others?