Why hollow guitars sound the way they do.
Our fascination with secret chambers is as
old as time. From childhood reading about
the Egyptian pyramids and Batman’s cave to
the modern-day Harry Potter books, something
mysterious and powerful resonates
within us when it comes to hidden rooms. For
centuries, the promise of treasure within has
drawn raiders and archeologists to Giza and
Mesoamerica, seeking knowledge, truth, or
wealth. Wise men knew that anything worth
having was worth preserving in a safe place,
and hidden chambers were intended for that.
In the world of instruments there is treasure
as well. For those who eat, sleep, and
breathe guitar, the list of likely places to
unearth harmonic wealth most certainly
includes hollow and semi-hollow instruments.
It is no surprise—these chambers echo with
the treasured tones of guitar history.
A Solid Perspective
Today, most guitarists forge their vocabulary
from solidbody experience and their tone-compass
finds “true north” within that limited
context. That’s because solid guitars brought
costs down for beginners, were “modern”
and flashy, and were suited to higher-volume
music, especially so in less experienced
hands. In the battle of the generations, solid
guitars became the weapon of choice for
youthful, loud, and aggressive music, but that
wasn’t always the case.
Before the era of electric guitars, there were
only hollow instruments. These early guitars
were engineered to reproduce sound
mechanically like all classical instruments. But
in an ever-escalating arms race with louder
horns and reed instruments, the guitar was
out-gunned for the solo spots. In retaliation,
guitarists began to experiment with ways
to increase volume. At first the fixes were
mechanical—birthing the resonator guitars
we know today, not to mention some wacky
derivations like the 1920s Stroh, which utilized
a spun aluminum diaphragm and horn.
These instruments were marginally louder,
but the tone wasn’t refined enough for most
types of music. For a while, it seemed as
though the guitar would remain a rhythm
instrument within the bigger band context,
but soon enough enterprising players were
equipping their fat “jazz boxes” with crude
electro-mechanical devices coupled to small
“amplifiers,” and the game was on.
My introduction to the electric guitar at age
10 was via a big, hollow Gibson with a pair of
black-cased P-90s that a camp counselor had
brought into the gymnasium for our entertainment.
It looked archaic, yet somehow
menacing with its array of knobs and lever
switch. That promise was delivered when he
cranked up a little GA-5 amp, and I heard the
Devil’s radio threatening to blow the windows
out of the building. I was hooked. Two years
after that, I got a solid Fender, but I never
forgot the lonesome howl that day in the
gym. It’s a tone that I still chase today.
Science Meets Sound
So what makes a hollow guitar tick? In the
simplest of terms, it’s the fact that it vibrates
more than a solid guitar. But to stop there is
an oversimplification. In my years of working
alongside aerospace technicians at our skunkworks
laboratory (affectionately referred to
as “Area 59”), I witnessed endless deflection
tests and scans of guitars using a laser
vibrometer. This pricey piece of equipment
takes a real-time computer “movie” of the
minute vibrations of a guitar’s surface, which
can be analyzed in order to “see” what you
were hearing when a guitar was played.
The relationship between stiffness and frequency
response can be mapped out pretty
convincingly using this stuff. It reveals to the
layperson exactly what good guitar builders
have known by the seat of their pants.
As the guitar top begins to absorb certain
frequencies of vibration from the strings,
converting it into movement, the top acts as
a kind of filter. The top (and back) are also
acting like a microphone diaphragm, picking
up the vibrations from the amplifier’s
speaker, feeding it back to the strings again.
All together, you get a very complex set of
reinforcements and cancellations.
Like a natural echo chamber, the size and
placement of the instrument’s chamber
will determine exactly what result you get.
Generally, the larger the chamber, the lower
the threshold is for interaction and at a lower
frequency. Some builders of semi-hollow
electrics harness this by creating several
chambers of different sizes to address different
frequency ranges. This alters an instrument’s
sensitivity. It’s usable sensitivity that I
look to create in making a hollow guitar, and
that balance takes experience to design and
build. That sensitivity can be rewarding to
master, but also can be intimidating at first.
Sonic Sensitivity
In practice, it’s a good idea to first approach
a hollow instrument with a clean, low volume
setting. This gives the instrument a chance
to reveal what it sounds like on its own. As
you add volume, you’ll reach a point where
your hand technique starts to really trigger
the interaction of the amp and the guitar.
This is what I call the first sweet spot, and it
really rewards the player who knows how to
work the strings fearlessly. Then, once you’ve
enjoyed that for a while, start cranking it up
and hold on. You may not be able to play
the way you’re used to, but that’s the whole
point. If you weren’t looking for a new ride,
you wouldn’t have bought the ticket.
Sometimes, players choose a hollow guitar
for the way it looks or the way they think it
will make them sound. But the hollow guitar
is more than a prop or tool for retro tone.
Because of its throaty response and predisposition
for singing along with your amplifier, it
actually can lead you to play differently. The
hollow or semi-hollow guitar’s willingness to
partner with you and the amplifier makes it
an ideal songwriting collaborator. Once you
embrace the places a hollow guitar will take
you instead of expecting it to just follow you
around to the same old haunts, a whole new
world of tonal opportunity awaits. Will you use
the knowledge found in the chamber for good
or evil? The answer is, of course, howl on.
Jol Dantzig
Noted designer, builder, and player Jol Dantzig founded Hamer Guitars, the first boutique guitar brand, in 1973. Since then, he has worked or recorded with many of the most talented and famous names in music. Today, as the director of Dantzig Guitar Design he continues to help define the art of custom guitar.