Can someone help me with speaker box calculations?

[Deer Killer]

When a datasheet quotes a particular volume, they mean that is the volume of the box without the driver installed? None of them seem to quote the total driver displacement, so otherwise getting a box with their exact specs will be impossible. i.e. Infinity Kappa Perfect 10.1d says "sealed box volume (includes driver displacement)" and then they have a vbox of .60 cu ft. If it is true that this volume "includes" the driver displacement then it is a really small volume of air. Crutchfield recommended box is ~ .75 cu ft (as calculated from dimensions) without a driver in it. So for example if I wanted to use a Polk MM2084 on the rear deck but build an enclosure (so it will not need to be free-air) it will be really small. They want .35 cu ft. 8" diameter, 4" mounting depth pi*8^2*4=804.23 cu in = .465 cu ft!!!! So if I build a cylinder as tall as the mounting depth (can probably pick up some pvc pipe scrap), I'd have more than the required volume????? If that's true they might as well make the speaker basket a sealed case, as a cylinder.... Do I have anything wrong here?

[Ninjapimp]

They used to have calculators here: [url]http://www.the12volt.com/[/url]

[Th3Franz]

It's pi r ^ 2, not diameter. And the displacement of a sub-woofer should be listed in its specifications if it's any good. :P You want to build the box with a net volume equal to the manufacturer's specs. So the actual box will be slightly bigger.

[Deer Killer]

ugh.. I'm an idiot.. ok that makes more sense.. but that's still quite small. There's a good amount of room above the trunk springs... But neither polk or infinity list driver displacement..

[Th3Franz]

Yeah displacement of sub-woofers is almost negligible, depending on the overall volume of the box. This is especially true for sealed boxes due to their linear audio properties. Ported or bandpass is a whole nother story....

[mcchicken]

I think an average 12" sub will displace between .15 and .18 3^ft. In a sealed box it's not as important to be exact as Th3Franz mentioned....nothing some polyfill can't offset anyway.

[Th3Franz]

[quote name='mcchicken']I think an average 12" sub will displace between .15 and .18 3^ft. In a sealed box it's not as important to be exact as Th3Franz mentioned....nothing some polyfill can't offset anyway.[/quote] Yeah that sounds about right for the displacement guesstimate. :D

[Subaguru]

The easiest way to determine volume is to use the calculations provided. All subs come w/ a recommended volume, and most even come w/ recommended dimensions. It's hard enough to calculate the actual basket size in order to subtract, therefore if the recommended dimensions don't work, subtract an inch here, add it there (i.e. 1" less in width, 1" more in height, etc.). Just make sure you're deep enough. Also, these are the recommended volumes, you're not going to be able to tell the difference of even .25 ft cubed. And if you are a little small, add some polyfill, it slows down the waves inside, making the box seem larger than it actually is. But just do something!! I want to see some pictures and hear reviews of some aftermarket upgrades. Best of luck.