The double bass is a big, fragile target. There's never been a
shortage of broken basses for luthiers to fix. However, I wonder
how much damage has been inflicted by poor lutherie compared to
the normal wear and tear a bass must face. Quite a bit I'll bet.
Nowhere is this more evident than the subject of springing a bass
bar. It's been portrayed in recent bass literature that putting
in a bass bar with spring is standard procedure and is accepted
as correct. Nothing could be further from the truth. Actually, to
spring or not to spring has been in debate for probably as long
as there have been bass bars. Before I go on, let me clarify what
springing a bass bar is and why someone would choose to do this.
Fitting a bass bar with spring is simply cutting it so it touches
in the middle and tapers out to a gap on either end as shown in
Fig. 1 (see right column). Those subscribing to this practice
would claim that the spring would counteract the pressure of the
bridge and help avert or correct a sunken top. Some also say that
the tension of the bar "spring loads" the top to make it more responsive.
I think "load" is the operative word there. No doubt, one can see
my slant here. Before I proceed, just let it be known that this
is just not my opinion here, most conscientious luthiers feel this
way. At some point in the future I intend to publish a more intensive
article in a bass periodical, but for my casual purposes here I'm
just going to quote one backing source. That would be the late,
great Hans Weisshaar considered one of our time's greatest experts
of violin restoration. He was the author of the book "Violin Restoration:
A Manual for ViolinMakers," which became the world's leading manual
on the subject. In this book Mr. Weisshaar emphatically states that
"Bassbar tension will not push the center of the table up, rather
it will pull the ends of the table down and consequently deform
them," He goes on to say, "Another theory states that an instrument
sounds better if the bar is fitted with tension. If the arching
is carved to produce optimum sound, why pull it out of shape?"
the subject of a sunken top plate-let's look at this a little closer.
Sinkage can occur basically in two forms, as shown in Fig. 2 (see
right column) and Fig. 3. Fig. 2 often is seen in older instruments
especially when the arching is relatively flat. Fig. 3 appears
more generally although it does occur at a high rate in basses with an
integral bassbar [one that is carved from the top]. Since an integral
bar cannot have spring this would lead on to believe that this sinkage
was caused by the lack of spring. This is erroneous and superficial thinking.
More on this later.
gives an instrument its structural strength? Is it the arching-the bassbar
- or the quality of the wood? The answer "d", all of the above would not
be a bad choice. But there is more to it than that. As with any equation
in lutherie there are many variables that combine toward the end result,
but there is a greater answer that speaks to my earlier question here.
This concept I learned from my old friend Xiao-Houng Luo a very fine violinmaker
from Shanghai. I had the good fortune to be chained to a bench for many
years alongside him. He taught me in a very "wax on-wax off" kind of way
to understand the structure of an instrument and most importantly - to
be motivated to constantly do better and better work and not worship profit.
So here it is - it's really rather simple. Take an egg. Put it end to
end in your palms. Clasp your fingers and squeeze. Perhaps a very strong
man can break it - I don't know, I am only a strong man and I cannot break
it. Why does the egg not break? Does it have a tension built into it to
counteract the force? Is it spring-loaded? Yeah, right. No, it has a perfect
shape, structurally speaking. It is much the same with a violin or a bass.
Take a look at Fig. 4. The pull of the strings creates a force
that seeks to shorten the top and lengthen the back. The blocks want to
act as levers towards this end. Looking at a viol from the side one can
see a roughly oval or egg shape in the structure. Of all the many things
that keep the instrument from exploding this is the most profound. People
talk about the arching, the wood quality, steel strings, the bassbar and
more. A properly built instrument will resist sinkage - but I don't care
how high the arch, how beefy the bar-if you loosen one glued surface of
either the neck block or end block there's gonna be hell to pay. The force
will have its way with the instrument and deformities will occur including
the sinking of the top centered at the bridge as in Fig. 2.
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