Originally posted by Bookforsaken
I have a good knowledge of electronics and cars decent enough anyway. I have seen this board off and on but am pretty new here. I have a couple of questions I would like answered and would encourage input. Because math speaking I suck. I can build stuff and have a good overrall sense but math I don't get and it seems to me that making a good sounding enclosure is kinda difficult if you build yourself. I want to make a box for 2 12's that will sit flush with the carpet like some of the other people have done on this board. Like going down into the stairwell. First of all would lining with fiberglass help at all or just using all of sound deadener for that kind of setup. I plan on using sound deadener inside the box. And Audiobahn recommends using polyurethane on the box before you put carpet on to finish it. I got the basic idea of what I need to build but I am trying to get a good box that will sound great. I see all these figures its like those the subs are 400 watts RMS a piece. Diameter of speaker is 12 1/8". Hole for speaker will be 10 7/8". Depth is 6 3/8. Displacement 0.23 cu. ft. Says recommend 2.26 cu. ft. And later on for sealed boxes says like sealed box minimum for a 12 is min. 0.75 cu. ft. And 1.5 cu. ft. maximum...says volume of box is h x w x d divided by 1728. I want to make a exact box for these subs but these figures mess with me. I am about to get the measurements for the trunk laid out. But would like someone maybe someone who has already done what does that mean for me building the box. Like some ballpark figures on lengths and widths...maybe a walkthrough if someone has them. Like I said I can build stuff well. But the match gets me. Josh

Well if your target inside airspace is 2.26 cu ft, then you need to add to that for the displacement of the sub( .23 cu ft), which means you need a total inside airspace of 2.49 cu ft. Sealed boxes are a bit forgiving with airspace, so round it to 2.50 cu ft. You have the right equasion of L W H divided by 1728. Just play around with those dimensions until you get the shape of box you want, equalling 2.5 cu ft airspace. Always pay attention to the thickness of the wood you are using, preferably 3/4" MDF. You will need to keep that in mind when finding external dimensions of your box. You can adjust the total airspace from the recomended, to personalize the tune of your sealed box. Typically, a larger airspace will give a lower resonant frequency(box will be louder at a lower frequency), and smaller airspace makes it boomier, and less loud at lower frequencies. If you listen to mostly rock type music, use the recomended airspace, if you listen to rap type music, if you can add maybe .5 cu ft of airspace. If you listen to all types really, and want the best all around frequency response, use the recomended airspace value.