What's Your Attachment Style?

…when attaching a guitar neck to a guitar body, that is

Guitar Neck

Note: this post is only about electric solidbody guitars, not hollowbody/acoustic guitars.

Let's start from first principles.

What must a guitar neck do?

  1. stay straight under string tension
  2. be playable
  3. minimize wood movement due to humidity and temperature changes
  4. withstand wear due to strings and fingers

What are some nice-to-have features of a guitar neck?

  1. be comfortable and not fatiguing for both chords (using all the strings) and bends (one string)
  2. low cost of manufacture
  3. low cost to maintain (increased durability and/or ease of repair)

The guitar neck has a different function from the guitar body. The neck anchors one end of the strings and is where the fretting hand does its work, while the guitar body holds the other end of the strings and makes the instrument more comfortable to hold or wear.

How do you make a neck joint? The most common methods are (in order):

  1. bolt-on
  2. glued-on or "set"
  3. neck-through

Bolt-on

This method of construction is simple, technically a lap joint reinforced by screws or bolts. It allows inexpensive construction. The body needs only a flat spot with some holes and the neck does not need any extra thickness, just enough so the screws don't protrude up through the fretboard. It allows a builder to use less wood for the neck, which further reduces cost because you can't just make a neck out of any kind of wood, it has to be a variety which is light, stiff, and stable.

Set

Glued-on necks almost always have more complex joinery, closer to mortise-and-tenon than lap joint. This provides 3 surfaces for glue (face and 2 sides) rather than just one (face).

Neck-through

This construction method extends the length of the neck past the fretboard, past the bridge, to the full length of the instrument. Typically two "wings" of material attach to either side of this neck beam to form a body. Sometimes a cap of material in front and/or back hides the joint, but more often the neck-through feature is visible. This method requires the largest amount of neck wood, which makes it the most costly in terms of materials.

Perceptions counfounded

Fender and Gibson are popular brands. In general, Fender bolts and Gibsons glues. It's a common claim that bolt-on necks are "brighter" sounding while set necks have more sustain (where brighter implies more high-frequency content). But is that claim due to the neck joint construction? Here are some confounding factors:

First, the pickup type is different. Generally, Fenders use single-coil pickups and Gibsons use humbuckers. Humbuckers are louder than single coils and have a different frequency response with more relative low frequency content than single coils.

Next, the two brands do not use the same scale length. Fender uses 25.5 inches while Gibson uses 24.75 inches. A string tuned to pitch over a longer span has higher tension and relatively more high frequencies than the same string at the same pitch stretched over a shorter span.

The type of wood may also have a small effect. Fender tends to use maple for their necks while Gibson uses mahogany. Maple is harder which theoretically favors high frequencies more than mahogany.

Finally, price is a factor. Budget instruments use budget construction methods, so they favor bolt-on. Expensive instruments can use whatever construction method they want, so more neck-through and set necks appear from high-end builders. Another factor that increases the cost of building an instrument is time and labor. Taking time to ensure all the parts fit correctly increases the cost of an instrument. Maybe you can see where this is going.

Objective reality

It's not easy to draw a direct causal link between how a guitar sounds and some isolated aspect of its construction. But Fender guitars tend to sound brighter than Gibson guitars. After considering these other factors, how confident should we be in attributing tonality to the neck joint?

Some things are measurable and objective, others are opinion-based and subjective, and a few things are impractical or impossible to measure and therefore vulnerable to myth-making.

Does scale length affect timbre?

Yes, this is something you can demonstrate with a guitar, a capo, and a spectrum analyzer.

  1. capo at the first fret and pluck or strum several notes, capturing the audio with a spectrum analyzer
  2. capo at the next fret, down-tune to the same pitches you had at the first fret, repeat the audio capture
  3. move the capo to the next fret and repeat until you get bored

The nice thing about this experiment is it keeps all the other variables constant - neck wood, neck joint, body wood, pickups, amplifier, and strings are all the same between measurements.

Does the neck joint method affect timbre?

This is harder to test objectively. But not impossible. Here's an idea for testing the tonal difference (if any) between bolt-on and glued-on construction.

During the construction phase:

  1. prepare a guitar neck and body for "typical" glued-on neck joint
  2. before adding glue, join the neck and body with screws, string and set it up, and record the guitar
  3. slack the strings, remove the screws, glue in the neck, tune back to pitch, and record again

As far as I know this has never been done, but even one such experiment would provide valuable evidence for the claims that guled-on necks are darker, more resonant, and sustain longer. If you wanted to be more accurate, instead of plucking/strumming the guitar by hand, you could use an electromagnetic exciter under computer control, to vibrate the string to a steady-state level and then measure its decay time.

How hard is it to replace a bad neck?

  1. bolt-on construction ⇒ trivial, anyone with a screwdriver can do it
  2. set neck ⇒ hard, risks damaging the guitar body, time-consuming, requires special tools
  3. neck-through ⇒ requires replacing 80% of the guitar

How hard is it to adjust the neck angle?

  1. bolt-on ⇒ trivial, screwdriver and shims
  2. set neck ⇒ even harder than replacing the neck
  3. neck-through ⇒ impossible

Opinions

Let's take the conventional wisdom at face value and assume a bolt-on neck results in a brighter timbre. Whether this is a positive or negative is a matter of taste, but it is inexpensive and electrically trivial to reduce treble with a passive and noiseless tone control (a capacitor and resistor). Most electric guitars have passive treble-cut tone controls anyway so this doesn't even change anything. So for me, this is a point in favor of bolt-on construction.

There is no way to add sustain to a guitar without trade-offs. Electronic dynamics-altering effects like compression add noise, and electromagnetic exciters like a Sustainer system add complexity and require batteries in the guitar. Therefore if set necks indeed have more sustain, that's a point in their favor.

Bolt-on necks offer ease of replacement and more adjustability than other neck joint types, +2 points for bolt-ons.

But what about comfort? Neck-through construction lets the builder make a smooth transition between neck and body which is more comfortable to play in the upper registers (near the neck-to-body joint). Some set neck construction does this too, like the seamless transition in Gibson's Axcess guitars. It's not easy to achieve a perfectly seamless neck-to-body joint with a bolt-on neck. However if the bolt-on neck joint occurs deeper into the body it is possible to make the part of the neck you can reach seamless and smooth. This isn't free as it increases the amount of wood required for the bolt-on neck (even beyond the amount required for a set neck with a long tenon) but it is an option. So in terms of comfort, every method gets a point.

There are some bolt-on (and glued-on) neck heel joints that are terribly uncomfortable with hard edges and angles. Any neck with a squared-off heel that is uncomfortable in the hand gets -1 point in my scoring system. This includes nearly all Fender designs and most Gibsons. What's the tally?

Table 1: unweighted scoring (0=bad, 1=good)
  bolt on set neck-through
build cost 1 0 0
repair/replace neck 1 0 0
adjust neck angle 1 0 0
comfort (typical) 0 0 1
brightness 1 0 0
sustain 0 1 1
total 4 1 2

Bolt-on wins easily even in the face of dubious claims about tone and sustain. Therefore my conclusion is that bolt-on neck construction is the best choice. But there is one important caveat to this: do not make a squared-off neck heel! This is just user-hostile design. Instead, countersink some ferrules in the neck and carve the body into a more rounded shape. Most guitar bodies are CNC-routed these days, and this step barely adds any complexity or cost to the build. But it makes for a much more comfortable instrument.