help on gross...

[tapout383 10+ year member]

it says my box has a gross of 7.48 Cubic Feet. What can i expect my net to be if i have two 6'' aeros with a 18'' Fi BTL old style with triple stack motor?

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[HlorridiXplorer 10+ year member]

ports external? add the volume of the ports to the gross.

ports internal? subtract the volume of the ports from the gross.

cylinder area = (pi*r^2)*Length

find the displacement of the subs on fi's website and subtract them from volume of the box.

 

[davescomptips 10+ year member]

ports external? add the volume of the ports to the gross.ports internal? subtract the volume of the ports from the gross.

cylinder area = (pi*r^2)*Length

If I remember correctly you never ADD the volume of the ports. Think of the port as a closed cylinder - they can not add to the volume of the box. Now, they can subtract from the volume. The amount they take from the gross volume depends on how many inches of the port is inside the box.

 

[EuphoricBass247 10+ year member]

right around 6.8-7.0cu/ft net depending on tuning

 

[tapout383 10+ year member]

ill say the ports are 6x15...radius would be 3 there internal woofer displacment is .25

 

[tapout383 10+ year member]

holy hell this was only supposed to be a 6.0 box lol dang o well more doesnt hurt i guess

 

[tapout383 10+ year member]

12.3 is what it says if its 6.8 cubes

 

[HlorridiXplorer 10+ year member]

If I remember correctly you never ADD the volume of the ports. Think of the port as a closed cylinder - they can not add to the volume of the box. Now, they can subtract from the volume. The amount they take from the gross volume depends on how many inches of the port is inside the box.

some people think that when you run external ports you have to add their volume because it is more air that the sub with my using along with the volume of the box.

I don't calculate port volume into any of my boxes because I tune my ports off a Termlab to where the system is the loudest and i'm constantly changing them so their length is constantly changing so for me to add in the volume of the ports would be stupid because their volume is constantly changing.

 

[davescomptips 10+ year member]

some people think that when you run external ports you have to add their volume because it is more air that the sub with my using along with the volume of the box.

It's more volume for the sub only because the port isn't in the box.

Look at it this way...

Fill your bathtub with water. Hold two bricks above the water. Did the water rise? No, there was no change in the total volume.

Drop the two bricks into the water. Did the water rise? Yes. The bricks add to the total volume.

Then explain to your Mom, wife, or girlfriend why you are washing bricks in the bathtub! //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[9BlackN*Black6 10+ year member]

It's more volume for the sub only because the port isn't in the box.
Look at it this way...

Fill your bathtub with water. Hold two bricks above the water. Did the water rise? No, there was no change in the total volume.

Drop the two bricks into the water. Did the water rise? Yes. The bricks add to the total volume.

Then explain to your Mom, wife, or girlfriend why you are washing bricks in the bathtub! //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

//content.invisioncic.com/y282845/emoticons/hilarious.gif.02a037aad04aa96f19982b298a3d70a8.gif

 

[tapout383 10+ year member]

ok so im getting ready to tune my box for my btl 7.4838 is what i have before aero and sub displacment...psp cacultor ask for box volume and im not sure what to put in as the volume of the box will change when sub and aero is factored in

 

[iamamp3pimp 5,000+ posts]

you designed it backwards.

now i will help you

well say that the sub is .25 cuft and the ports all together equal about .73 cuft

take your gross and subtract 1 cuft, put in your port info 3 6" ports 15" long

and see what it tells you.

 

[iamamp3pimp 5,000+ posts]

thats if ports are internal.

if they are external, they dont factor into anything at all.

so in your case, gross - 1 cuft = net

 

[iamamp3pimp 5,000+ posts]

did you build it already?

 

[tapout383 10+ year member]

um i built it already but havent cut the ports....