Outside to inside volumes?

[Mexar 10+ year member]

If I have a box of say 5.585 cubes on outside dimensions, anyone know what my actual volume would be, given 3/4MDF ??

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[GAM3OVR 5,000+ posts]

is it a ported or a sealed box?

 

[GAM3OVR 5,000+ posts]

cuz then there is also port displacement....

 

[Mexar 10+ year member]

Outside box dimensions gives me a total of 6.905 cubes.

I lose some to some bumps in my trunk (whoops) for a total of 1.32 cubes lost.

Leaves me with 5.585 cubes left, and yes it's vented (Slot port from the bottom, approx measurements would be 31" X 2" X 12.5" deep.

Woofers are .083 cubes for displacement each (x2)

 

[Mexar 10+ year member]

One other question... is a 31" X 2" slot port bad? my port length calculator tells me not to be bigger than an 8:1 ratio?

 

[chunky cumz 10+ year member]

its a prefab isnt it?

 

[Mexar 10+ year member]

Nope, building it as I type... just hard to figure out with the bumps and such, was wondering if there was a simple(ish) calculation to figure it out using wood thickness (3/4) and outside volume with displacements figured in already...

 

[Mexar 10+ year member]

Anyone?

 

[Immacomputer 10+ year member]

So you designed the port parameters without knowing your box volume?

Stop the build right now. Slow down and figure out all the information before you end up with something that sounds like complete shit and is nothing like what you were expecting.

Take as many dimensions as possible and translate those into a 3D CAD program like Sketchup and use that program to see how much space you have to work with and that way you can find very accurate net volume numbers.

And yes, you should absolutely avoid a 32x2 port as your tuning calculations become severely skewed as you're moving too far away from an idea port shape (round) and setting yourself up for port noise and shifted tuning.

 

[Mexar 10+ year member]

I'm building the box to absolute max possible sizes for my car, so I only have outside measurements until it's built... I don't feel like sitting here for 3 hours with a calculator to get box volumes.

I don't actually have the port designed yet... it's laid out at the 32X2 atm, but not cut. Suppose I'll have to build the box , measure the volume then re-lay out the port... probably go with a 10X6 or so in that case

 

[Immacomputer 10+ year member]

It won't take 3 hours first off, second, even if it did take 3 hours, it would be WELL worth it.

Can you make lines by clicking a mouse button and then moving it a certain distance? If you can, you can use sketchup. Sketchup is free and very easy to use. You can make complex shapes, right click on them, and instantly find out the area (remember area times height is volume. That's not using a calculator for 3 hours. They make this stuff so anybody can use, no matter your math skill levels.

Don't rush things or you will spend 5 times as long doing 10 times as much work as you could have done if you planned things out correctly.

 

[Mexar 10+ year member]

Tried using Sketchup, didn't go so well... couldn't even get the port in how I wanted it =P

Thanks for the attempted help, maybe I'll just draw it out 100% and plug away at the calculator

Or just start long on the slot and tune from there =P

 

[Mexar 10+ year member]

3.71 cubes after all displacements, port of 10" X 5" X 18.25" deep... should tune to 35hz

 

[TSGP]

give the measurements you have and i'll tell you the box size and what its tuned to

 

[Mexar 10+ year member]

Thanks for the offer TSGP, but the box is 90% built, minus the sides and port

It was an utter FAILURE!!! **** thing didn't fit in the car... stupid sloped side walls!

Full sheet of MDF pretty much down the drain, but I'm not giving up yet!