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Having a box slightly too big will give you a larger peak around tuning, and worse performance elsewhere generally speaking.

That said, 2cuft is just fine for those subs.

The tuning of the box would be lower if you kept the port length the same(and the area) while making the box bigger. But just putting a sub in a larger box doesn't lower the tuning of the box. The box is tuned to what it is tuned to. So if the manufacture recommends 1.75cuft tuned to say 35Hz, you'll be fine with 2 cuft tuned to 35Hz. Or you could tune higher or lower based on your tastes. Honestly subs don't require a certain volume to work. You could put your 12s in a 20cuft box if you wanted, but you would end up with a greatly reduced mechanical Power handling, a huge peak at tuning, and a response that would probably sound like crap. Conversely you could put it in 1cuft and tune to 35Hz as well, there would be no peak at tuning and it would likely start rolling off much before the 35Hz tuning(and thus you would be sacrificing output). The mechanical power handling would be increased.

Hope that helps.

Originally Posted by -0nes-

well i did finish the box today i let the glue set in for like 4 hrs and got anxious so i hooked it up an i did notice every thing u mention but i dont hit the lows as good as the other box i had but still sounds good having one 15 hooked up now i need to set the other one as soon as i get it

Good stuff...but...
The reason you are not getting much low end is because your port is 2 times too wide.
Once you get the other sub in it'll be ok.
But right now the one chamber is seeing a port 2X too wide(it starts out at the right size, goes around the bend and then it's 2X too wide.

So once you get that second sub it should have a better low end.