According to my math, the volume displacement of an Infinity Kappa Perfect 12.1 is about .25 cu ft.
For a 1.75 cu ft box, Infinity recommends a 4" diameter x 12.33" long port. I'm not sure if you should add two ports for two subs, or simply double the size of the port, I'll leave that to the experts.
Are you trying to put it in a sealed or ported box? A sealed box would not require you to measure displace because a sealed box's sound is not dependent on exact box volume. If you are building a ported box i'm sure you could get away with a rough measurement.
If you are trying to measure the exact displacement of the subwoofer inside the box, there are many ways to go about measuring it.
The first one that comes to my head is putting the woofer in something that is water-proof like say a trasbag. Then you could immerse that in a tank of water and measure how high the water rises. That with a little bit of conversion from liters or w/e to cubic feet would give you a pretty precise measurement. Like I said though that is kind of unneeded haha.
how many db should 2 12.1's pull in a 3 cubic foot ported box tuned to 38 hz. How much power can these subs really handel their rated at 350rms each but ive heard they can take 500 rms before! idk that sounds fishy to me but idk.
what do u mean i edited the first post? i dont even know how to do that. but if i did i would have to combine my first and second posts ( the one after urs was my first) ok so im gonna factor in .4 total cubic feet loss into my calculations i figure that should be a safe caluve to work with.
hm i dont know i could have sworn you were asking about how loud it would get, maybe it was the same sub in another thread. you can edit your post by going to your profile looking at your recent posts and clicking edit.