This article goes beyond basic banjo setup and seeks to explain the difference between standard banjos and Nechville’s helically mounted banjos. If we want to judge sound differences between the two types, we must determine what effect the mechanical differences impart upon the sound. Being very subjective, each players’ opinion as to what constitutes “best” may vary.
While it is difficult to define the positive tonal aspects of the best banjos that truly tug at our emotional heartstrings, it is obvious to most players when a negative sound such as sonic dissonance or a mechanical buzz is present. Likewise bad intonation caused by imperfect fret or bridge position is measurable attribute that we can minimize with good building and set-up practices.
String vibration is a natural phenomenon that delivers a fundamental note plus sub vibrations of the string called harmonics. It is the job of the bridge, head and tone chamber, or “banjo pot” to transduce the string’s vibration into the sound that we hear. Complex variations in the pressure applied upon the stretched membrane through the bridge, defined by the string’s harmonic signature, compress and stretch the air on both sides of the head. This causes sound waves, which are further processed by the instrument’s body.
It is the intent of this article to consider just what are the sources of unwanted frequencies or dissonance that can interfere with the purest sound that a banjo can make.
The tradition of simply using our ears and a long process of trial and error has given us the banjo we use today. What if we wanted to design a banjo of pure sound, without distractions from unwanted resonances? A quick look back into banjo building history may shed some light on this.
The mechanical hardware in a common bluegrass banjo consists of 24 hooks, nuts, metal flange, metal tension hoop, two metal rods acting as bolts and stabilizers for the neck and body connection, plus the hardware needed to anchor strings to the body. All these metal connections were not particularly designed to affect the acoustical tone but they can and do impart a metallic nuance to the regular banjo’s sound.
In our ideal virtual design of the banjo pot, we run into a complication when we bolt the neck to the tone ring and pot. Scientifically as well as intuitively, we want to find a design that separates and frees the acoustical components from the mechanical/structural ones.
An advancement in banjo design in the 1920’s allowed the tone chamber to nest into a one or two piece flange that allowed for fewer metal hardware attachments directly to the cylinder of the tone chamber. Fewer mechanical attachments to the tone chamber must be a factor in generating a better tone, since banjos based on the Mastertone of the 1930’s continue to dominate even in the bluegrass of today. The Gibson design, however, still depends on the neck being bolted directly to the tone chamber with a dual coordinator rod system.
It was not until the mid 1980’s that Tom Nechville brought us Helically mounted banjos, or Heli-Mounts. In the world of Nechville, the neck bolts to the integrated hardware of the Heli-Mount frame. This allows for insertion of the tone chamber from the back of the frame and is compressed in place without any metallic stress or unwanted resonances. The Heli-Mount yields automatically even head tension while extending the rationale of the Mastertone design to its ultimate fulfillment.
More information on Nechville and banjo design is available at www.nechville.com.