View Full Version : Calculating sealed box resonance (f3)

09-11-2013, 05:52 AM
Ok so I'm still trying to design this 4th order but not before I completely understand everything first.
I found somewhere that to find the F3 of the sealed chamber (or any plain ol sealed box) is used by a simple formula....

[(vas/vb)+1)^2] x Fs .... Assuming both vas and vb are in liters, I should with a certain vb shoot for an F3 of 45 hz correct? Or could I shoot for a lower F3 in the sealed chamber since I want to tune my ported chamber @ 40hz to pound lows??
The problem I've been having is I do this equation with the woofers I plan on using (American bass TNT) and I keep getting an F3 that's EXTREMELY high.

Here's the math with a sealed box (vb) of 2.25 cubic ft (63.712 L)....
[(77.2/63.712)]+1}^2 = 4.89 ...... 4.89 x 32.2(fs)= 157

What am I missing here? An F3 of 157hz is just stupid and no matter what woofer I put into this equation comes out this way. I've changed box sizes as well.. Is it my equation?

I just want to know so i can put these 2 15's in the best possible box for the output I want (LOOOWWWS)....

Somebody help me out here. I'm trying to figure everything out myself but as you can see, I'm having troubles.

09-11-2013, 12:30 PM