Calculating Cu. Ft. in a glass enclosure

water seems like it would be a bad idea cuz i know someone would be stupid enuff to put it in, and not dry it COMPLETELY, then you have 12 volts runnin through wires and ur car catches fire, but then again, to the one who has or is going to do it.......u most likely deserve it

one other thing you can do is mark the square box in .25 cubic foot increments. this will help you be a little more exact when you are measuring. i have always used the packing peanuts and it has worked very well. another option is to make an adjustable port. that way you can test it once it is done and tune it the way that you want it to sound.

I would get some type of frequency generator and actualy tune your enclosure to your liking.Just play with the port length in the general volume you think your close to.When the woofer stops moving but is very loud that is what your tuned to.