View Full Version : Sealed Enclosure Calculations help

12-01-2004, 11:06 AM
ok so i am here at www.diysubwoofers.org trying to find out how big of an enclosure my 2 Lanzar MAX12's need.

according to the website i need to do this:

(Property of www.diysubwoofers.org credit goes all to Brian Steele for his work)
To determine the box size for a sealed enclosure system, you will need to know the following Theile/Small parameters for the driver:
Vas = Equivalent air compliance (litres)
Qts = total Q of the driver at Fs
Fs = resonance frequency of the driver (Hz)

Choose a final Qtc (total Q of system at resonant frequency) for your design. Recommended values for Qtc are from 0.6 to 1.0. Transient response degrades with higher Qtc values, but the power handling of the system increases. A Qtc of 0.7 will usually give pretty good results, but you can use a higher figure if the subwoofer has a low resonant frequency (<20 Hz) or if it's being designed for car use.


Qr = Qtc/Qts
Vr = Qr^2-1
Vb = Vas/Vr
Fb = Qr*Fs
F3 = Fb*((1/Qtc^2-2+((1/Qtc^2-2)^2+4)^0.5)/2)^0.5

If Qtc>(1/2)^.5
then dBpeak = 20*log(Qtc^2/(Qtc^2-0.25)^0.5)
Else dBpeak = 0


Vb = net box volume (litres)
Fb = box resonant frequency (Hz)
F3 = -3dB frequency (Hz)
dBpeak = maximum peak or dip in system response

1. Now, i take it that the Vb is what i need for the amount of air inside the box. How do i convert that to Cubic Feet? Better yet Cubic Inches?

2. If i wanted to make a sealed enclosure that is seperated in 2 sealed compartments that can house 1 subwoofer in each compartment (thus 1 single large enclosure housing 2 subwoofers, do i need to just use the same formula for both sides of the box or will i need a new formula?

12-01-2004, 03:19 PM
or you could just look in your manual or online and find the manufacturer reccomended enclsure and do it that way

12-01-2004, 03:46 PM
i already did, but they don;t tell you what size to make the enclosures and i have emailed them about it but it's been about a week and no replies :(

12-01-2004, 04:04 PM
1 liter = 0.0353146667 cubic feet just for asome people to know.

12-01-2004, 05:11 PM
1 liter = 1000 cc
1 ci = 16.387064 cc
1 ft^3 = 1728 ci
1 ft^3 = 1728*16.387065
1 ft^3 = 28316.84659 cc
1 ft^3 = 28.31684659 liters

So if you get say 100 liters and want to convert it to ft^3, you divide by 28.31684659 to get 3.531466672 ft^3

you do realize that you just made the solution seem more complicated? Iono about you but i went online and googled it. Liter to Cubic Feet :|

12-01-2004, 05:14 PM
STOP IT! lol

Footius Maximus
02-24-2005, 11:39 PM
Probablly anywheres from 1-2cu.ft for each sub.