-closed
 -vented
 -4th order bandpass
 -6th order bandpass

ISD can calculate optimum box size to first 3 types.
ISD also can draw frequency response plot to all 4 types.

All you have to know is your driver's Thiele/Small parameters:

Vas = equivalent air compliance
Fs = resonance frequency of the driver
Qts = Total Q of the driver at Fs

If you don't know those parameters you can try to locate driver's parameters from my Driver database.

1) Hit 'New Driver'- on top of ISD-page

2) Now you can enter your driver's parameters to corresponding text-fields,
    or try to find driver by name from database.
    NOTE! It is always better to use measured parameters of driver,
    than using ones from database

3) When applet has appeared you can choose two different ways to finish your design:
    - You can just click "optimum" button to calculate optimum box size to your driver
    - Or enter your custom enclosure parameters by hand and see how nice
    response curve we can have :-)

4) If you have to calculate vent length, then you can use my vent calculator
    ('Vent calculator'-tab on top of ISD-page).

Closed box:

Vb = box volume in X unit

Vented box:

Vb = box volume in X unit Fb = tuning frequency of box

4th order bandpass:

Vf = volume of front chamber in X unit Vr = volume of rear chamber in X unit Ff = tuning frequency of front chamber

6th order bandpass:

Vf = volume of front chamber in X unit Vr = volume of rear chamber in X unit Ff = tuning frequency of front chamber Fr = tuning frequency of rear chamber

This util can be used for calculating vent length.
if you are calculating vents for 6th order bandpass box,
then you must calculate each vent separately. For rear chamber
vent, place Vr to Vb and Fr to Fb. For front chamber vent,
place Vf to Vb and Ff to Fb.

Notes:
By X unit I mean that, when you specify drivers Vas in litres then result
volumes is also in litres.
When you specify Vas in cuft then result volumes will be in cuft. And so on...