Ken Cartwright: The Bridge - Can We Do Better?
Most of us take the bridge on our mandolins for granted as a device that holds the strings up so that the mandolin can be played.
But, what is the role of the bridge in sound transfer? Do we want to change the sound and tone of the instrument? Does the bridge affect the loudness and "in tuneness" or intonation? Can it improve the tone of the instrument if the bridge is changed? What research and improvements already have been done to better the bridge? What works and why? What doesn't?
Until several years ago, I--like many others--didn't think about the bridge much beyond adjusting the height of strings and making sure it was in the right place so that the mandolin played in tune. Through the last 43 years of repair, I have seen a lot of variations of bridges on a variety of instruments; however, I was too busy doing general repairs to experiment with bridge design changes that would improve the sound. But, that all changed in 1994 when a special mandolin came in for repair and set up.
"Musicians needed more volume and better tone"
Before I tell you about that, let's look briefly at the evolution of mandolin bridges. Prior to 1900, mandolins were mostly round-backed, European imports with low-profile bridges that sat on flat surfaces and had little or no arching. There was little variation in design and since the bridges were not adjustable, if one was too low, either a new one was made to fit the height or shims were added to bring it up to the needed height. If the action needed to be lowered, the bridge was taken off and material was removed from the bottom of the bridge.
These Neapolitan instruments were somewhat difficult to hold and play and the spacing of the frets made it difficult for many to finger. As the world of music expanded, musicians needed more volume and wanted better tone.
A young man from Kalamazoo, Michigan, had been re-designing the mandolin with these changes in mind. Orville Gibson built flat-backed instruments. He increased the angle of the neck in relationship to the body. This greatly improved the volume and tone over its European cousin. The top of the mandolin changed from a mostly flat top to a curved top, and the new surface and height requirements meant a new bridge design.
Orville Gibson's mandolins and guitars became very popular and a company was formed to produce these new, improved instruments for the world.
In the early 1900s when the Gibson musical instrument company was producing mandolins and guitars from its Kalamazoo facility, the bridges for mandolins were wood only and hand fitted to the shape and contour of the top of the instrument. These one-piece bridges were of solid ebony, sometimes rosewood, with the correction for intonation carved into the top of the bridge by hand until 1905.
At that time, Gibson began experimenting with adding slots to the top of the bridge and inserting saddle pieces to correct intonation and improve string wear. This bridge design was used on all Gibson mandolins and L-Series guitars until the early 1920s. Today, the tone of those Gibson Mandolins is referred to as dark and rich. The bracing on those instruments was simple horizontal bracing, being more of a design for support than tone.
"The adjustable design has been attributed to Lloyd Loar"
As mandolins gained in popularity, Gibson found that hand fitting and manufacturing this bridge was very labor intensive and that there also was a need to adjust the bridge height quickly for player preference and also changes in humidity and settling of the instruments.
Thus the adjustable bridge was born. The adjustable design has been attributed to Lloyd Loar, a Gibson design engineer. Bracing, neck angle and top graduation also was being re-thought in order to give the mandolin more power and a new voice as the instrument soared in popularity and prominence in American music.
Other changes were also in store as people experimented with inner tone chamber devices such as the Virzi tone producer (more about this in another article), different wood choices, new finishes, scale lengths, nut materials and body size and shapes.
Through the years, much experimentation has been done with bridges and materials. We have seen one-piece bridges with wood only, wood with bone as well as solid, one-piece ivory bridges and many variations of the adjustable bridge.
Not much was done to improve bridge design from the mid-1920s until the early 1970s when mandolins began to enjoy a comeback in popularity and production. A young luthier in New York City by the name of John Monteleone was commissioned by Mandolin Brothers to build less than two dozen exact copies of a specific F-5 Gibson Lloyd Loar that had come to them for repair and restoration.
"There was a 'special bridge' in the case"
One of these mandolins was brought to my shop several years ago by the original owner who had purchased it new in 1976 from Mandolin Brothers. He wanted fret work, cleaning and setup.
As I was examining the instrument and going through the setup, the owner informed me that there was a "special bridge" in the case that had been on the instrument when he bought it. The bridge on the instrument was a typical adjustable bridge that he had installed later because he couldn't use the "special bridge" as it was not the right height--the strings rattled, etc.
Upon examination of the setup of the mandolin, an exact copy of a Loar F-5 which the label inside the instrument verified--"an exact copy"--I noted that the truss rod was extremely loose and therefore the neck had too much bow and that the adjustable bridge had to be cranked up very high to clear the frets at the 15th through 19th frets. The owner explained that he had never adjusted the truss rod. He just thought it had the wrong bridge on it. The instrument was loud, but hard to play with the adjustable bridge--but it was better than with the "special bridge," which was too low and rattled.
What happened when I put the "special bridge" on the mandolin? Read this column in the next issue of Mandolin Magazine--The "Special Bridge" and an Amazing Discovery in Tone.
Ken Cartwright, owner of Cartwright's Music Repair in Stayton, Oregon, began repairing violins and guitars in Pennsylvania at the age of ten in his grandfather's fiddle shop.
He completed an indentured-servitude apprenticeship in instrument repair and setup from 1969 to 1971 in Los Angeles and an internship with Guillermo Combreras in Michoacan, Mexico.
From 1973 to the present he has worked full-time in stringed instrument repair, restoration and also training luthiers in Oregon's only luthier-apprenticeship program. Cartwright's Music recently moved from Salem to Stayton, and was formerly Natural Sound, Salem and Coos Bay.
Ken Cartwright is president of the Salem Area Bluegrass Association and producer the Annual All-Oregon July 4th Bluegrass Festival and Contest. He plays guitar, mandolin, fiddle, standup bass and other stringed instruments.