How to calculate air space in a f/g box?

Im getting ready to build a fiberglass sub box but i need help calculating the air space i know how to on other sub boxes but now with the different shapes like a molded f/g box...any help would be nice...

look at it from the side and measure out the full area and make a scaled down drawling on a piece of paper. Break it down into shapes that can be measured and get as much of the space as possible into the shapes. Then do the same thing from the front and from the top to get your LxWxH and the add all the areas together. Depending on how much space cannot be calculated in this method add a .1cuft or 6 depending on how much untill you feet that its close. Its not a 100% accurate way to measure the space but it can get you close. Theres otherways like filling it with sand and measuring it with a cylender formula but those methods are messy and sand isn't light in bulk so its not always practical.

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"Shiny chrome when used in conjunction with bikini models is particularly effective in inducing brain deficit disorder"

02 Jeep Grand Cherokee

Monster System on its way.

Use the sand. Also, try searching for this post cause its been asked a lot.

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dream it, build it, fiberglass it

the easiest method that i have found is taking packing popcorn or packing foam.  You can usually buy big bags of it at office supply stores or any post office.  You can figure out how many cubic feet that you  need for the speaker and convert it from cubic feet to litres.  After that just take a juice jug or something with a litre measurement on it and start tapping that up and dumping the foam into the enclosure jug by jug until you have the required litres.  Remeber that 1 cubic foot of volume is equal to 28.32 litres.

Why would the packing popcorn method make a 5% +/- difference??

the way the packing peanuts settle

there are air gaps in packing materials

but there are airgaps also in the box with the peanuts in the box.  So wat is the difference between airgaps in the litre measuring jug....compared to air gaps in the box?

I would have to agree..... if you take a cardboard box made to 1 cu-ft....  fill it with the peanuts... then that amount of peanuts will alwyas be 1 cu-ft no matter how they settle.... the air gaps you get in the final measurment are present in the first measurment...

im sorry but i have to disagree the most acutate way is water displacement or sand other than that your just making a educated guess

Oh i wasnt meaning to say that the packing peanuts is a 100% accurate way to measure the volume... however i dont think your put off by 5%. 

u guys know subs have those readings for enclosures that are put as .5-.75 cuft for that reson. Its a give or take kind of scenerio especially with fiberglass. Silvers right, water or sand would be the most accurate but I'd have to say that the packing peanuts would be the most economical and least messy of the two.

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"Shiny chrome when used in conjunction with bikini models is particularly effective in inducing brain deficit disorder"

02 Jeep Grand Cherokee

Monster System on its way.

just use sand

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dream it, build it, fiberglass it

im with ya

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i agree that sand and water with, with no airgaps would be a more exact way of measurement....but it is much less of a hassle to just use packing foam instead of lining it with grabage bags and then using water and all that trouble.  The easiest way if you are just making a enclosure for yuourself in your car is to use packing foam.  If u are going for exact measurements for SPL or SQ purposes then sand or water would be the most acurate.  But i just thought that the educated guess and the 5% comments didn't really have anything to back them up.

well think about it if you take a piece of packing peanuts and pour them from one box to another then shake the box you'll hardly ever get the same amount shown just because of the air space and the way those pieces lock together granted 5% might sound like alot, but think about what 5% of 1cuft is it not that much to worry about at all say your box is around 5, 6cuft or bigger then yes the packing peanuts method will not get you dead accurate but it will get you a educated guess (how you ask well to put it like this if you fill up a 1 cuft box with them and let them settle then that equals 1cuft then pour that amount into your box well since you dumped the peanuts in i don't think they stayed in the same arrangement that they where in the original box you measured from but now you think your box is full and you think you have the airspace figured out wrong shake the box alittle and watch your little peanut puff settle agian so you pour in more and more until its so full that every piece is locked in place then you tell me that you know that the amount of packing peanuts used is exact i say bullsh*t but thats IMHO

I think he was asking how to calculate the air space before building the box.

so how do measure the air space before you build?

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CASHRIDER

You eye it out and make good guesses with rough measurments. Its better to make the box to big than to small. You can always take away volume but its hard to add it.

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dream it, build it, fiberglass it