I’m struggling. I need help building a ported box for two Audiofrog gs8’s. I have built several sealed boxes, but never a ported. Is it as simple as building a chamber for each sub to spec and then adding a round port to each.
Bear in mind that you'll need to add the displacement of the port, driver and any bracing to the specified net cabinet volume in order to determine the needed gross cabinet volume. The port should be of sufficient area to prevent possibly audible port noise at the power applied and/or the desired level of output.
Net cabinet volume, port area and port length are what determines tuned frequency (Fb) of a ported design. The larger the cabinet, the longer the port and/or the lesser the port area, the lower the Fb (and vice versa).
Modeling software such as WinISD helps to determine suitable cabinet volume, port area and length, and tuning frequency (among a number of other factors) for a particular driver and application.
You can also build slots into the box. A little more complicated and takes up more space in the box because the wood is thicker than the cardboard or plastic tubing.
But the slot port can also act as bracing making the box more better.
But In your case with these woofers and your first time. I would use the tubing.
If you can get the fitment tight enough or even use duck tape to seal the tube into the box. So you can try different lengths for different port tuning.
Since it's your first build. I would try experimenting before gluing anything.
God point about experimenting with port length to find what sounds best. I forgot to mention that. I'm partial to flared (aero) tubular ports like these Precision Ports at Parts Express: https://www.parts-express.com/search?order=relevance:desc&keywords=Precision Port
I use packing tape in conjunction with the connecting rings to temporarily attach tube pieces together until I settle on a length that sounds best and then glue them together permanently.