Many customers do not realize Warmoth has been around almost 30 years. Custom instruments and repairs were our major businesses in the early days. We’ve repaired or replaced hundreds of bass necks. Over the past three decades, we’ve seen a lot of broken-down, worn-out, warped and dead Fender Bass necks. We experienced the usual issues of constant truss rod adjustments, s-curved necks and dead notes. In our opinion, the prime suspect in a most cases was the Vintage truss rod. It is the source of the inevitable "S-Curves" at both ends of the neck, the high action and need for seasonal adjustments. It is also responsible for those dead notes that don't have the same volume or sustain as the other notes. Duplicating the construction of those necks and their inherent shortcomings did not make sense to us.
To remedy these problems, we investigated many different truss rod designs and found much to be appreciated in the double expanding truss rod. This rod is more rigid with more evenly distributed pressure. This design proved excellent at eliminating virtually all the problems with notable exception of the dead spots. We continued our research by experimenting with different types of stiffening rods. Over a hundred experimental necks were built using graphite stiffening rods and they did not make the dead spots go away….
Steel provided very even responsiveness with virtually no dead notes. The conclusion we reached is that neck rigidity is not the sole factor in eliminating dead spots. Additional mass plays a significant role as well. A simple exercise to illustrate this point would be to gently attach a C clamp on the peghead of your bass. Notice the increase in sustain it brings? Further, if you have a dead spot, notice that moving the C clamp can move the location of the dead note!
These changes are blasphemous to the vintage crowd, but we believe a craftsman is known by his tools. The Warmoth Pro construction bass neck is the result of our experience and research into building a great bass neck.
Warmoth Pro Bass construction
Vintage Bass Neck Truss Rod
This truss rod is anchored to the neck at both ends. This single rod is typically 3/16" in diameter and threaded 10-32. One end is a fixed anchor and the other end is an adjustable anchor. Key to the function of this rod is the concave slot or trench in which it is installed. Tightening the adjusting nut causes the rod to straighten thereby exerting upward pressure in the middle of the arc.
The red arrows indicate the compression forces exerted lengthwise upon the neck. The blue arrows indicate the forces bearing up on
the center of the neck. The yellow arrows indicate the resulting neck movement determining string action height and corresponding relief.
Benefits of the vintage truss rod
- Light weight-minimum mass
- unique tone-replicates vintage tone
- inexpensive to manufacture
- least torque required for adjustment
Drawbacks
- requires frequent adjustments with seasonal humidity changes
- compression of the wood lengthwise causes eventual wood distortions (lumps and bumps in the fretboard)
- Deadspots, most commonly around C# on the G string
Double Expanding Bass Neck Truss Rod
Our truss rod is a double rod, either made of two pieces welded together or a folded single piece. This design has been used by Rickenbacker for many years. The double rod is installed directly under the fretboard in a straight trench approximately 3/8" deep and is not anchored to the neck. A long adjusting nut is used to focus the truss action away from the unmovable heel joint.
When flexed in the neck, resulting pressures are shown above. The blue arrows show the two rod ends exerting high downward forces while the middle pushes up uniformly. The resulting neck movement shown with the yellow arrow, determines string action height and corresponding relief. The force exerted by the tail end of the double rod is considerable. There must be a minimum 1/8" of wood below the rod end to prevent wood failure in this area. This becomes a concern only when thinning a neck beyond factory engineered dimensions.
Benefits of the double expanding truss rod
- Extremely stable, no seasonal adjustments are necessary
- Increased mass = longer sustain, cleaner and clearer notes
- Even frequency response
- No end to end wood compression to eventually distort the neck
Drawbacks
- Greater weight than vintage rod
- More torque required for adjustment
- More expensive to manufacture
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