Audio Systems: Help to build speaker box, acoustic impedance, acoustic parameters

Question
I am Savio From (India) recently my friend brought a Home theater and it sounds really very good.I thought to buy one but its costly so now would like to build one my self one thing i noticed in that  the subwoofer speakers are fitted some were in side the speaker box and just a small hole in the front of the box to let the sound out and i want to know where the speaker are fitted & how or is there any system kit also in side the box. I have made a diagram about the s/box from my idea but i can,t attached it with this messege so if u can give ur mail id i can send that to u and u can get the clear picture what i am thnking about
waiting for you promte reply
thanks
savio

Answer
http://www.the12volt.com/caraudio/boxes4.asp#1

Above web page will show you various kinds of bass reflex enclosure designs.

The role of the box is to achieve the movements of the cone/diaphragm of the driver into sound pressure radiation to the listener.  What happens at low audio frequencies is that air travels omnidirectional and if not prevented the air pushing out from the back side of the cone will just move around and cancel out the front side movement.  So, the box or cabinet must be designed to prevent that while at the same time not adding too much restriction to the free movement of the cone.  It requires advanced acoustic theory to fully understand the physical and acoustic principles.  However, the volume of the cabinet and the acoustic impedance of the vent are all directly associated with the acoustic parameters of the bass driver unit.

You can send me the diagram to cleggsan @ ieee.org  (but delete the spaces).

C

PS: Here is a discussion on the basic design of a vented box.

http://en.wikibooks.org/wiki/Acoustics/Bass-Reflex_Enclosure_Design

There are similar tutorials for closed box designs.