Is it possible to make a decent sounding ported box ( for 10" Alpine Type R) with these dimensions?

16 - 17" wide
16- 17" tall
bottom depth 12"
top depth 10 "

I want the box to taper from bottom to top so I can snug it closer to the rear seatbacks.

 

@ 17"x17"x10/12" you only have a little over 1.32cuft. Alpine recommends 1cuft but thats after displacements. It could be done, but going to be really tight with them tolerances.

 

Slot port calculator. 17x17x10/12 with a 1" port is 1.2 cubes @ 48hz.

RE Enclosure Calculator

30
13.5 height (.75" spacing)
10
12
.75
2
24.5

1.359 @ 34 with 2" wide/24 square inches. Your rear seat doesn't have much of an angle. My rear seat is more like +8" at the bottom.

25 x 15 x 10/12/.75" MDF/1.5" port #1 20.5 port #2 = 1.354 @ 33hz, change the height to 14 and you have 1.253 cubes, so after displacement 1.2 cubes @ 33hz is pretty good, if you can get 25" width.

What are the exact max. dimensions for width because you need more width to get a lower tune.

 

I've tried that box calculator but unfortunatly it alway puts the port on what would be the back of the box. I could possibly make the box 18" wide. Maybe 13" at bottom.

My last ported box was square 15 W X 15 depth x 13 high, tuned to 38hz. Sounded good but with the shape , had to be another 3-4 inches from the seat.
It barely left enough room to put a golf bag, let alone a hockey bag in the trunk.

Also if ported wont work, is there any reason not to go with alpines 0.65 cu recommendation for a sealed box . And, how do you factor in that number with the area that the woofer displaces?

 

You would do 0.65cuft + subwoofer displacement = internal box volume without sub.

 

You'll need a triangular port calculator.

 

RE Calc.

30
17
7.23
9.23
.75
1.3
25.9

1.25 cubes after displacement (.05), 16 square inches per cube @ 32hz.

1.3 x 15.5 isn't great though.