I want to build a In-Floor subwoofer for my home theater. Does anyone know how to come up with the calculation for the sound translation through the vent for the port?
What size should I get. How thick should I go? What size port?

Wow, you've got some balls.

But i'd recoomend buying one still, long before any built in thing. Unless you're pushing some serious stuff like B&W Nautilus speakers, or better...

but a good place to start is the forums at www.audioreview.com.

What'* your budget?

Right now , I can't afford an expensive system but I want to build the box and use for meanwhile. I would like to have the quality so in the future I can upgrade the Sub and still have a great box.
Budget 1100.00 - 300 for cables and connections = 800.00
1000.00 for the amp( must have wired remote controls)
Any Idea'*

Go to ADIRE AUDIO and download the demo of LspCAD , YOu can use it to calulate box volumes and port lengths as well as get frequency response graphs and such. Its a free demo.

http://www.adireaudio.com/Files/Adire.zip