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Every summer
since 2003, I’ve been a participant in the Acoustics Workshop sponsored
by the Violin Society of America at Oberlin College in Oberlin Ohio.
This gathering, co-directed by D’Addario string engineer Fan Tau and
violin maker Joseph Curtin, consists mostly of accomplished professional
violin makers and scientists who study the physics of violins. At the
2004 Workshop, there was one participant who didn’t really fit either
category-Douglas Martin-a maker of competition rowing shells who had
made a few bizarre, strangely shaped violins out of Balsa wood. It was
evident to me and to Joseph Curtin that even though they were strange,
they were nevertheless acoustically amazing. One Balsa violin in
particular had very unconventional neck dimensions and a very crude
bridge. I helped Doug to reshape the neck and since one of the projects
going on at the Workshop was a study of bridge acoustics with several
world class violin makers participating, I said “Doug, there’s a whole
row of world class bridge fitters, why don’t you get a decent bridge for
this fiddle?” That was done and the result was an even more remarkable
sounding violin which now felt much more normal to play. That evening, I
was hanging out in the hallway with Joe Curtin as we passed Doug’s Balsa
violin back and forth playing it and marveling at its sound. I could see
the wheels turning in Joe’s head as he played it and we agreed that
despite its weirdness, this violin had power and responsiveness matched
by few if any conventional violins. Later the legendary violin restorer
Rene’ Morel who was a faculty member of the concurrent Violin Setup
Workshop came in with a group of Setup Workshop participants. Seeing the
Balsa violin, someone said “Rene’, can you set up this violin?” Rene’
was equal to the challenge and pulled his sound post setter out of his
pocket and darn if he didn’t make it sound still better! By this time
the Balsa violin sounded really great. The following day, while we were
waiting in line for our group dinner, I had the opportunity for an
introduction. When I said “Rene’, this is Doug Martin who made the Balsa
violin” Rene’ said to Doug “You made that? That’s the best sounding box
I ever heard!” Well that’s probably a big exaggeration, but coming from
the man who has probably had on his workbench more great Cremona
masterpieces than anyone else alive, it’s obvious that he was impressed!
In the time since then I’ve been trying to understand why that Balsa
violin worked so well. One reason I think is basic high school physics,
F=MA (force equals mass times acceleration). If the mass of wood that is
set in motion by the force of the bow to in turn vibrate air (sound is
vibration of air) is reduced, the effort required to produce that sound
will be proportionally reduced. That explains why the violin was so
amazingly responsive, but I’m sure there’s more to it than that. There
are three physical properties of wood that are critical to its effect on
the sound of musical instruments. They are stiffness, density and
damping. Stiffness and density are easy to explain and measure but
damping is much more complex. I think Balsa has damping properties that
are unique and desirable for bowed instruments. Balsa is not very stiff
but is extraordinarily low in density. Because as any engineer knows,
the bending stiffness of a beam is proportional to the cube of its
cross-sectional dimension in the direction of bending, a beam (or violin
top) that is twice as thick will be eight times as stiff. So, if that
top is half as dense (Balsa can be half as dense as Spruce) and half as
stiff (Balsa is about half as stiff as spruce) but twice as thick, it
will still be twice as stiff overall for the same mass! What this means
is that using this unique material, it is possible to make an
extraordinarily light weight instrument which will have approximately
the same structural stiffness as a conventional one. Furthermore this
instrument can have the unique damping properties of Balsa.
Scientist/violin maker Ted White, who lives near me, was a participant
at the 2005 Oberlin Acoustics Workshop. Since we were both excited by
the possibilities of ultra-light Balsa instruments, and Ted makes
violins while I make basses, we decided to collaborate on making a Balsa
wood ‘cello! We wanted to make something that pushed the limits as far
as we dared but would still feel completely conventional to a ‘cellist
and look at least a bit more normal than Doug’s instruments. We realized
that to take maximum advantage of the new materials, we couldn’t just
substitute the new material into a conventional design but would need to
use a different structural design. We completed the ultra-light ‘cello
(made in only 2 months!) in time for it to be demonstrated at the
November 2005 convention of the Violin Society of America in
Philadelphia. Since that time, I have invited many top-flight ‘cellists
to play it and to my amazement, there has been very little negative
reaction to its appearance or unconventionality. The usual scenario
proceeds from initially being afraid to play it vigorously for fear of
breaking it to realizing that there is no problem playing it normally
and then being amazed at how good and powerful the sound is and how
easily it plays. A typical response came from a Chicago Symphony
‘cellist who said “when can I get one of these?” Ted and I are working
on the next version of the ultra-light ‘cello with the intention of
making an instrument with a more professional standard of workmanship
for eventual sale. I also plan to make an ultra-light bass, viola and
violin. Stay tuned!
A few details: The ultra-light cello weighs about ½ as much as a normal
‘cello. The ribs are a sandwich of Balsa between Maple veneers made
using the same vacuum technique that I use for my bass ribs. The neck is
made of Maple but hollow and reinforced with a carbon fiber tube. The
scroll is made of laminated Maple veneer. The top and back were made of
flat panels of Balsa using a computer and CNC machine to create
templates for cutting out the panels with the exact shape required such
that when glued together, they would bend to the same long arching shape
as a Strad. ‘cello. There is a bass bar in the usual place but there are
also two “treble bars” one on the top and one on the back with platforms
for the ends of the sound post to rest on. Of course I had to give it an
adjustable neck!
Here are some pictures of the ultra-light ‘cello. In addition to Ted
White and myself, I’ve included pictures of Norman Pickering and the
late Oliver Rodgers. These men are giants in the world of string
instrument acoustics and I am greatly privileged to call them friends.
The ‘cellist in the photo is Roman Borys of the Gryphon Trio who
demonstrated the ‘cello at the Philadelphia VSA convention.
I've also included a photo of Doug Martin and his amazing Balsa violin. |
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