Is the phone case itself bulging ? Do you see any separations at the seams of the phone case ?
The speakers, located in the bottom of the phone are connected by a pressure connection clip (a small metal prong that contacts the main board) The connection is dependent upon the main board being held in position by proper assembly.
There are 6 screws (T-5 or T-6) located in the back of the phone, be sure they are tight and unbroken.
Watching the 8220 disassembly video on cnncn.com will help you to better understand what I am telling you so take the time to go to this link and scroll to "8220 disassembly" and click on it.
YouTube - wwwcnncnxxx39;s Channel