Violin Sound Post Setup
The purpose of violin Sound Post is: One, to support the top violin sound box plate
Two, to transfer the vibrations to bottom plate
Sound post can have enormous effect on the sound quality and loudness of the violin, thus it is often referred to as the Soul of the violin.
The position of the sound post inside the violin is important, its effect varies with violin construction, but general trend is demonstrated in Fig1.
Note. Some lateral position change (from A to B) is possible with the same Sound Post. In Fig 2 we marked a spot at the edge of the sound post after it has been placed while strings were loose. It shows that when strings are tightened the sound post does not move as far towards the side while set with the same lateral force. This means that after the A and E strings are tightened the dimensions of the sound box would be changed, thus giving further variable to affect sound. It would make sense that using shorter or longer sound post will not give same effect as moving the same sound post laterally.