I'm Looking At Building A Ported 8 Cubic Foot Box For The SSD 18. Someone Couldn't Help Me With The Dimensions And Port Size, Could They? I'd Seriously Like...Appreciate It. Also Specs For A Square Port Or A Slot Port, And How You Make A Square One. I Suppose Its Just A Hole In The Box Panel? The Sub Is Firing Up, Port Firing Back.

Per your PM - 49"W x 18"H x 24"D will work. I made it 49", because that is the width of a sheet of MDF

Make the top of the box 1.5" thick, all other sides 3/4"

The port will be a square opening on the back side of the box that will be on the driver's side. Make the opening 15.75" High (that is 18" - 1.5" for the wood on top - .75" for the wood on bottom) x 6.5" Wide. One side of the port will be the side wall of the box (making it a "slot" port) the other wall will be a piece 15.75" High that will extend into the box until it is 7" from the opposite wall from the port opening.

That Would Be Tuned At 33hz, Correct? Thank You, By The Way.

It will be around 32-33.

I find over 4" wide ports don't seem to follow the 1/2 width reduction for slot effect, but in this case you also have some of the rear corner length that adds on to the length, since the rear opening is almost the same width as the port.