I currently have a 2005 single cab Dodge Ram 1500. I recently ordered a Sundown Audio SA-8 D4 v.1. I have a 1k Hifonics Mono Amp i was hoping to push this sub with.

Im having issues getting a box design. I built my own and friends boxes but only merely guessing needed airspace and very unfamiliar with tuning. I under stand its got to do with the driver, box volume and port length and size but beyond that im a noob. From reading around I've seen that these subs need about .5-.75 cubs of box at about 30 to 40hz? My first box attempt was around .6cubs but the port was about 1"x8" and only 27" long which im almost positive is incorrect because the sub will not even do any notes below 40hz with tones.

I need some assistance on where i should start box wise and if it would be possible to fit 2 of these subs in the back of my truck. To give and idea of what the space is like I currently have a 4.cub box with 2kicker 12's behind the seats. the box is around 40+"x11x14. Im sure there's room is mainly the videos from YouTube with these subs with ports bigger than the actual box space is what scares me. I appreciate the future help.

lets define some terms the rest is simple math

-gross volume. total volume of the box without any displacement calculated (external dimensions)

-net volume. volume of the air space after subtracting port displacement, sub displacement, bracing, etc.

-port displacement. volume of air occupied by the port inside the box

-sub displacement. volume of air occupied by the subwoofer inside the box

-port area- self explanatory

-port length- hope this is too

so the net volume for the sa-8 you say is .5-.75 cubes. that means that after all displacement you need .5-.75 cubes of space.

i didn't go over your numbers to see where you made a mistake.

google the appropriate online calculators and figure things out.

You need a lot more port area. A 1x8 is way small.

It is tricky to build a single 8 box tuned correctly. It will not be a small box.

You could try a passive radiator. Jacob did some testing with a psi 10" with good results.