What's so important about neck angle? - Aug/Sept 2002
The Physics of Neck Angle
Acoustic stringed instruments create sound by creating air pressure waves that begin with plucking or bowing of a string. String vibration transmits to the body (through the bridge/saddle & the nut & neck.) The air chamber in the body amplifies the vibrations & makes pressure waves. Because the angle between the neck & the body affects the strings’ interaction with the nut & the bridge/saddle, neck angle affects transmission of vibration from the strings to the body. Proper neck angle drops away from the plane ofthe instrument.
Instrument builders & acoustical physicists & engineers have studied the relationships between neck angle, string length & string tension for many years. While the subtleties are still under study, the underlying concept is simple:
1) greater string tension equates to better transmission of vibration
2) longer string length requires higher string tension to reach pitch
3) greater neck angle supports longer string length
4) proper neck angle allows optimal transmission of vibration.
Neck angle affects playability. Too low an angle raises the strings far from the fingerboard, making the instrument hard to play. Intonation also suffers from poor neck angle & high action.
Reasons For & How to Recognize Poor Neck Angle
Low neck angle is a progressive condition in stringed instruments. String tension, high temperatures (that soften the glue in the neck joint) & time work together to gradually rotate necks upward from their original position. So, old instruments & those that have been strung with heavy strings or have suffered exposure to high temperatures tend to have poor neck angles. Low neck angle in a new or nearly new instrument can result from the builder setting a low neck angle OR a weak neck joint that allows rotation early in the instrument’s life. In either case, a neck reset will be necessary sooner than in an instrument of the same caliber that has a better neck angle. Indicators that neck angle is low include high action (that is worse up the neck), a bridge/saddle that is very low, & finish cracks where the neck & body meet.
What can I do? How & When to Correct Problems
Instruments with better materials & construction develop problems later, but movement is inevitable in any glue-joint under constant tension. Eventually, the neck must be removed & reset. A neck reset is major surgery. So, lowering the bridge/saddle & using lighter strings should come before a neck reset. When your saddle/bridge are as low as they can go, it’s time to get the neck reset or get a new instrument– depending on the value of the instrument. Neck resets involve a lot of expert labor hours & can cost over $400.