Originally Posted by 97teg

Just measure and approximate figure its as pretty much a box. If its off by a little then its not a big deal. Do length x width x height (all in inches)/ 1728. That will give you the cubic feet. Sealed encolsures arent that particular if they are off by a bit it wont really matter that much.

The enclosure size will depend on the power. If you are towards the max of the woofer you probalby want to be on the smaller size. You will trade size for efficiency and in some cases low end extension. That is where the extra power comes in it can make up for these problems. The smaller box size will allow the sub to take physically more power before it starts moving to its max and parts start hitting other parts. If you are beyond the limits with regard to heat however, it will do nothing for you. A bigger box increases effiency and tends to increase the low end so if you are on limited or lower power it helps. You can always build the box a bit on the big size then add foam or something inside the box to reduce the airspace until you get it where you want it. If its a bit small then you can add polyfill (basically pillow stuffing) make the speaker "think" its in a bigger box. So you have some wiggle room a tricks either way. Id probably aim for 1.5 cu ft and then take away from that depending.