im thinking about getting an xcon 15 but wanna see if i should use my old box or make a new one. old box is 3.4cf after displacement using 2 4inch pvc ports tuned to 30-31hz. would that be good enough for an xcon 15 or should i go bigger? amp will probally be a kicker kx1200.1 or something similar.

Take a look at the box designs under the XCON banner at the SSA Store. That box should work fine. The XCON will be a monster in a ported box!

You can start with that size box and see if you like it. You can go larger if you want. Check out the technical center for box designs for the Xcon.

That box will work fine.

Go bigger, you have about 7.38 square inches of port area per cubic foot and it calls for 12-16. They don't need 1750W but it'd be a little louder with more power so shoot for 1500-2000w if you can afford a new amp. 1200W @ 1ohm is enough power. There's a big difference between an Atlas on 300W and an Xcon on 1200W. Try the recommended 4 cubes @ 26-33hz with 64 square inches of port area (16 per).

Aero ports require less Sq" than slot ports.

Go bigger, you have about 7.38 square inches of port area per cubic foot and it calls for 12-16. They don't need 1750W but it'd be a little louder with more power so shoot for 1500-2000w if you can afford a new amp. 1200W @ 1ohm is enough power. There's a big difference between an Atlas on 300W and an Xcon on 1200W. Try the recommended 4 cubes @ 26-33hz with 64 square inches of port area (16 per).

i was told that those specs are for slot port boxes an when using areo or pvc ports that you could cut the port area number in half an still be ok is that true? if not would 2 5inch pvc ports work?

im thinking about getting an xcon 15 but wanna see if i should use my old box or make a new one. old box is 3.4cf after displacement using 2 4inch pvc ports tuned to 30-31hz. would that be good enough for an xcon 15 or should i go bigger? amp will probally be a kicker kx1200.1 or something similar.

Your box fits with in the box requirements, you should be fine.

You're gonna love the Xcon!

I've heard the 18" in person and it was

Of course try your current box but if you're not happy, what do you have to compare to? With a great sub you might as well skip to a new box to get all of it's potential. You have 25 sq.in. of port area and need at the minimum 40 to be inbetween (if aeros are more efficient) a better 14-16 per, so shoot for the minumum rec. slot port port area and you'll get better results. Unless aeroports cut the needed port area in half (no), you need more port area. Don't bother choking it, but how are you supposed to know if you are? Do a slot port with 4 cubes & 64 sq. in. of port area for a better result.