Your Bass Playing The Way You'd Like
Part 1 I discussed the importance of the fingerboard as the
foundation of the set-up. Now Id like to get into the
other major components of the set-up, and how they affect
the bass sound and playability.
simple softwood dowel held in place between the top and back
plates by the tension of the strings, the soundpost is an
important structural entity, as it keeps the top from sagging
under the treble-side foot of the bridge (the bass bar performs
this function under the bass-side bridge foot). But it also
performs important roles in a string instruments sound
and response. Some luthiers believe the post serves to transfer
vibrations from the top to the back ; others believe it is
simply a stiffening rod, creating a pivot point for the top
to vibrate around. I think both these theories have merit,
and I also believe that moving the soundpost has an affect
on the swinging of the bass bar, the engine of
the bass soundboard. There are several other theories
as well, but for the purpose of this article Ill stick
to the practical ramifications of soundpost fitting and positioning.
The fit of the soundpost where it touches the back, and especially
the top, is crucial. This is important for both tonal/response
issues, and for the health of the instrument. It is especially
important that the post fit securely against the soft top
wood, to avoid creating a dent, or worse, a crack in the fragile
softwood top plate. Some luthiers (myself included) file a
tiny relief bevel around the soundpost ends, to help prevent
splitting of the post and abrading of the top when the post
is moved around. I have seen several soundposts fitted with
a huge bevel which reduces the contact by about half; this
can do nothing good for the tone or response, and can actually
cause a split in the top table. Any bevel needs to be tiny
or the installer cannot tell if the soundpost actually fits.
If a soundpost is fitted with no bevel at all, it is important
to remove any fuzz or splinters around the ends, because otherwise
a nasty buzz may result.
In general, the soundpost should be located laterally (east-west)
just about opposite the bass bar. So if the bass bar is encountered
65mm in from the bass-side f-hole, the soundpost should be
located about 65mm in from the treble-side f-hole. It should
be located longitudinally (north-south) about ¾ to
1¼ diameters below the bridge foot (toward the tailpiece).
So, if the soundpost is 18mm in diameter, it should sit about
14-22mm or so below the treble-side bridge foot. I usually
start a soundpost fit-up by putting the post opposite the
bass bar and one diameter below the bridge. I call this the
neutral position. Keep in mind that the bottom
of the soundpost needs to sit squarely under the top, with
most cases I do not adjust a soundpost until I
have first fit it well in the neutral position. This spot
works well most of the time. After a little playing-in,
the bass owner and I will determine if adjusting is
necessary. The posts position can be changed if the
player wants more or less of a certain type of tone and/or
response. Rarely do I adjust a soundpost more than about 5mm
in any direction. The effects of soundpost repositioning are
usually quite subtle, but sometimes eye-opening. Id
like to state here that soundpost adjusting is a bit of a
black art, and that sometimes the result makes
no sense. I am convinced there is some magic involved.
is my take on some basic guidelines to bass soundpost adjusting:
more bottom: Away from the bass bar.
For more punch: toward the bass bar.
For a more open, resonant sound: Away from the bridge.
For a tighter, more controlled sound: Toward the bridge.
sometimes encounter a bass that responds differently than
is typical to soundpost position changes. Often, the only
way to find the sweet-spot is via time-consuming
trial and error. This can be really frustrating, and I personally
can only handle about an hour of this before my ears and patience
tinkerers out there, please keep this in mind: most position
changes will also require re-fitting. Thats because
the surfaces to which a soundpost fits are complex curves,
often irregular as well. This is a job for an expert, especially
in an old carved bass. Doing the job right requires lots of
light, proper tools, mirrors, and huge reserves of patience.
Im not saying a talented and well-equipped do-it-yourself-er
should not tackle this job, but there are consequences to
doing it poorly. Installing a soundpost with its edge pressing
into a grain of the softwood top table can cause a serious
crack! And a soundpost should never be moved around with the
strings tuned up! If a luthier starts knocking
your soundpost around without first taking down the string
tension, get out of there fast! This practice can tear shreds
of wood out of your bass top, whether its carved
Ideally, the soundpost should fit just tightly enough to stay
in position without strings on the instrument. But seasonal
changes and short-term humidity swings can have a major effect
on the posts tension. Round-backed basses are better
able to handle these variations, as the back is more flexible
than a flat-backed bass with stiffening back cross-bars. Many
flat-backed basses require both a summer and a winter soundpost
to sound and respond their best.
issues are very often related to the tension, or tightness
of the post. Violinmakers rely on a simple axiom: A tight
post equals a loose fiddle, and vice-versa. This is often
true of basses too; however, basses change dimensions so much
(because they are so large and their wooden parts vary so
much with climatic conditions) that it is impossible to always
have the soundpost set with optimal tension. But when a bass
is misbehaving, checking the soundpost tension can be the
key to improving its response. To complicate this further,
some basses sound/respond best with a tight-ish post and others
with a loose-ish post. An overly-tight soundpost may manifest
in a bright, squashed sound. An overly loose post can make
a bass sound flabby, wolf-y, and slow to respond. And then
there are the exceptions
soundpost must be in place during bridge fitting and adjusting.
In my next installment I will delve into the bridge and nut,
the other major components in the set-up of the bass.
I anticipate doing a few Q and A columns in the future, and
would appreciate hearing from you folks out there who have
problems with your basses, or just want to expand your knowledge
regarding our noble instrument. Please send your questions
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