I just did the upgrade, and my little bro has a JBL 12" sub that is in a faily large ported box, I just wonder if the volume is close???

My sonotubes are 56 inch tubes (16 inch diam - same as the SVS) which give a volume of 6ft^3 or 170lt. If the total height of the SVS is 31 inches including baseplate, Im guessing it would be about half the vol of my sub, 3ft^3 or 85lt. Download this program, you enter the dimensions of a sonosub and it calculates the volume for you. Harry.

Harry, thanks for the reply. I didn't want to download the program, but based on your measurement. I can figure it out. I would guess the inside of mine is about 26.5" long (28.5 end to end on the outside), that would make it about 2.84 cubic feet (wow, that is a lot of volume to replicate in a box, the JBL I am guessing is only about 1/2 of that, So I guess it might not work?

putting the origional SVS driver that is designed for 2.84 cubic feet in an enclosure that is only 1.45 cubic feet (as a replacement/upgrade for my little bros JBL sub)

Isn't the equation for volume of a cylinder (pi)r^2h? If you use inches, just divide by 1728 to get ft^3(1ft^3 is 1728^3in. Measure the tube part of the sub, subtract about 3in for the endcaps. There you go... EX: say the tube is 27in internal, since the tube is about 16in diameter use 8^2(pi)x27/1728=3.14 ft^3 You will have to plug in the exact numbers but I believe this is the correct formula(I hope).

Fill the SVS with water up to the top and measure what you take out. You'll have exact volume. Forget all these formulas.

I have always heard that insolation makes it so driver sees the volume as larger (maybe unless you pack it in tight), I don't know though.

I screwed up on the JBL box size, it is actually 18"X16.5"X16.5" on the inside, so that should make about a 2.815 cubic feet. perhaps I should head over to the DIY section, those guys seem to have all the answers.

Jeff your volume of a cylinder equation is correct: V = r x r x pi x h But remember that the port and driver take away from this. Measure how long the port is and use 4" for diameter. Use the cylinder volume equation and take that away from your total. Then a 12" driver will take roughly 3 litres away from the total as well. The end result will be the actual net volume of the enclosure. For how stuffing affects the appearent volume of an enclosure check this article: http://integra.cyberglobe.net/caraud...ces/fiberfill/ Bottom line was that with small enclosures (less than 2ft^3) stuff at 1.5 lb/ft^3 and you'll see a 30% increase. As enclosures get larger it gets harder to fool the driver. Once you start getting up over 3 ft^3 drop it to 1 lb/ft^3 and you may see as much as 25%. Get up over 7-8ft^3 there becomes little point is stuffing anymore (just line the walls with polyfill batting). My sizes for switching are rough guessing as the article doesn't get specific about that.

Dustin, he won't need to find the net since the SVS has the sub and port in it as well, so as long as the two volumes match, he should get the same performance right?

Oops, should have read the first few posts more carefully. If this is for cloning purposes correct. If this was for modelling the SVS enclosure with different drivers and ports no.

Adding fiberglass will increase the apparent enclosure size a bit. If you are trying to build a *box* version of the 25-31....go with about 3.75 ft^3...tuned to the 25hz range. If you line the majority of the box with 2-3" of glass...just use a 1.2x multiplier to figure box size.(so if it's 3 without glass....figure 3.6 with). TV