My (yet another) Tempest Sonotube Update (1 Viewer)

[Aaron D]

Ok, I'm getting close to building this thing (on the 7th and 8th of July) and I just want to double-check myself. (Sorry to post another one of these.)
1. Anyway, I'm looking at a 230 L tube (24" dia). My understanding is that the port volume "replaces" some box volume, so I will add some to the tube dimensions to account for the volume of the port.
2. The tube will be 25% fill (Qa of 30), so for a tube of 230 L, this means I'll add about 2.2 lbs of fill?
3. Finally, for a tune of 15 hz, I need a 4" dia port of 35.7 cm long.
I can't help the feeling that I'm forgetting something, so if anyone spots trouble, please say so!

On another note, I have concocted a quite unique design for my enclosure, but I don't wan't to reveal it yet just in case it won't work!!

I will post some pics as soon as I get it built, though.
Wish me luck, and THANKS!!
Aaron

 

[Julian Data]

Aaron,
Be sure to include the volume of the driver which is 5L.
The port volume is given by using the equation Vol Cylinder = PI(r²)Length
The result will be in CU³, to get to FT³ divide by 1728. And then to covert to liters from fT³, multiply by 28.325.
For you case:
I assume you are using standard PVC and not the "thin wall" type? If so..
=[3.14(2.15)²(14.055")]/1728 = 0.115386 (28.325) = 3.268L
So..
Your NET volume is 230L
GROSS volume would be adding the port, inside endcaps (2 of them - one on top and bottom : 2(24" DIA * 0.750") and driver in your case. 230 + 5 + 3.27 + 11.12 = 249.39L. If you were doing a box, include the braces.
Cut the 24" tube to a height of: 33.750" which gives a GROSS Volume of 250.27L.
As for the fill question, you need need 2Lb for 25% of a 8FT³ box.
------------------

 

[Aaron D]

Julian, thanks once again!!