Frank, i don't know how it went for Alex.
I've changed both the earpiece (speaker), also the flex cable for the sensor/front camera. "[product|IF118-005]
Due to the copper plates was unforunate ripped from the flex cable(very easy to do), i've installed the new cable as well as a new speaker and still no progress.
I begin to wonder if it may be that it is some dust or fat on the surface of the connector or the copperplates or the spiral contacts, i will try to clean it. But i'm doubtful this will help.
Also there is no success when trying to pinch the phone right near the speaker when placing a call(read in some forum that it could work due to a glitch in the connection).
Too bad nobody seems to have a real solution or answer for this problem even though a lot of people are experiencing the same problem. This happend to me when i changed the screen so maybe a bad screen? Although everything else are working fine!