In Part II of this blog series, we discussed briefly how the bridge and sound post work together as a fulcrum and lever system. In this continued discussion, we will outline a few of the guidelines and considerations I give to the sound post.
Some of this information may seem arbitrary, but is based on a combination of my training and 40 years of experience observing and setting up countless instruments from all schools, countries, and periods of violin making.
When choosing the wood for a sound post, there are a number of considerations that should be given thought. First, one must determine the grain pattern of the top wood, i.e. how close are the annual rings, and how stiff or flexible the arching appears to be from both side to side, and neck to saddle. It seems to work best if you can match the grain pattern of the sound post to that of the table. But there are certainly other considerations when choosing the particular piece of sound post material for a particular instrument.
From young Engelmann spruce, to 16th century Italian spruce
I have a collection of sound post wood which varies from high-altitude, 35+ year old Engelmann spruce, to 16th century Italian spruce which came from the floor joists of a 16th century house in Italy. I like to use Engelmann because it is incredibly lightweight and has all of the properties I seek for the transmission of vibration from the top to the back. It is extremely fast, and allows me great variability in choosing both the grain pattern and the actual width or thickness that I have determined to be ideal for a particular instrument. Hardness of the particular piece of spruce chosen for the sound post is also one of my many considerations when setting up an instrument.
For a 17th or 18th century instrument, I sometimes like to use my very old and well-aged wood, if I can find a sample where the grain pattern and the apparent hardness of the wood seems to match the top wood in the particular instrument I am working on. But if I determine that the lighter weight and flexible Engelmann is more appropriate, I don’t hesitate to use it, no matter how old or how “important” the instrument happens to be. Again, I can’t emphasize enough how important the choice of wood is to a successful result. This is just as important as placement in relation to the bridge which will be the subject of our next discussion.