1. Measuring the thickness of the carved top using a Hacklinger gauge. 2. The results of my soundboard
measurements. 3. The instrument’s back is made of beautiful bookmatched flame maple. 4. Though the
headstock has a cello-like scroll, it’s drilled for mechanical bass guitar tuners, as opposed to friction pegs.
This month we’ll examine
a very rare and captivating
stringed instrument from
Gibson. At first glance, it
appears to be some hybrid of a
cello and an old-school bass guitar.
The sales receipt that came
with the instrument offers a few
clues to its origins. The receipt
is dated November 3, 1981, and
the seller’s address reads “Gibson,
225 Parsons St., Kalamazoo MI
49007.” The instrument has a
product number of 389999 and
is described as a “Cello Bass.”
All this leads me to believe
that someone at the former
Gibson factory had an idea for
a new instrument and began
building a prototype—likely
during the ’70s. Clearly it was
an unfinished project that
was later to be sold off “as
is.” The groundwork was laid
by Gibson, but there are still
many mechanical designs to
work through and questions to
answer about how the original
builder intended to make it all
come together.
In my initial examination,
I could see that the fretboard
was not only previously slotted,
but—thanks to telltale imprints
from fret barbs—frets had been
installed at one time. After they
were extracted, a rosewoodcolored
epoxy mix was applied
to fill the empty slots.
The body and neck appeared
to have no structural cracks,
just some superficial scrapes
and dings. Interestingly, the
neck angle does not provide
sufficient height to work with a
cello-style bridge. I realized that
before I could string up this
cello bass, I’d need to design
a bridge with a much lower
profile. My plan is to sculpt a
simple bridge—something with
a traditional look that’s compatible
with the instrument’s
overall appearance.
The tuner holes have already
been pre-drilled for a geared
bass guitar machine, as opposed
to the friction pegs you find on
cellos and upright basses. I’ll
use Madagascar ebony for making
the nut and selected maple
for the bridge. At this time, I’m
hoping to use a traditional cello
tailpiece and an adjustable steel
endpin. We shall see!
Restoration and rebuilding
jobs always begin with careful
measurements. I was really
looking forward to determining
the thickness range of the
carved top. For measuring
assembled instruments, I use
the Hacklinger Thickness
Gauge (item #4090 from
stewmac.com). A precision tool,
the gauge is calibrated for thicknesses
up to 8 mm and accurate
to 0.1 mm. This tool helps
luthiers graduate tops, backs,
and sides, and it’s also great for
measuring vintage instruments
without damaging them.
Gibson Cello
Bass Specs
• 34"-scale rosewood fretboard
with a 7.25" radius and plastic
dot inlays
• Three-piece neck consisting of
a maple/rosewood/maple laminate
• Cello scroll headstock
• Two-piece quartersawn Sitka
spruce top with maple sides and
bookmatched flame-maple back
• Laminated wood purfling on top
and back
• Two parallel Sitka spruce tone
bars that run longitudinally
underneath the soundboard
It works like this: A small
plastic-coated magnet placed
inside the instrument is attracted
by a magnet in the gauge
that rests on the soundboard.
You measure how far these
magnets are separated and this
distance is expressed in millimeters.
The interior magnet
follows the movement of the
gauge along the top, even over
braces up to 20 mm thick.
To protect the soundboard’s
finish, I inserted a 1.5" x 1.5"
piece of cotton polishing cloth
between the underside of the
gauge and the instrument. Then
I simply moved along the top,
recording the measurements
on a sheet of paper. Using the
Hacklinger, I determined that
the top of this Gibson cello bass
measures between 4.3 mm and
6.5 mm in thickness.
Rather than over-think this
project, I simply want to come
up with a reasonable and logical
solution for completing an
unusual instrument that was
started 30-plus years ago. I look
forward to sharing my progress
in next month’s column.
John Brown is the
inventor of the Fretted/Less
bass. He owns and operates
Brown’s Guitar Factory,
a guitar manufacturing,
repair, and restoration facility
staffed by a team of talented
luthiers. His guitar-tool and accessory designs
are used by builders all over the world. Visit
brownsguitarfactory.com or email John at
info@brownsguitarfactory.com.