physics behind bolt-on vs thru-neck

[pilotjones]

Problem is that a laminated beam runs the full length beyond the nodes where stress is induced, a neck joint on a bass does not, making things inherently weaker. (typically)

In comparing the neck through, almost all the stress is applied axially, so for that stress, the neck acts like a column with the weakest point being the area of thinnest cross section. (near the nut) However, since the force is applied from one side rather than the absolute ends, there is a small, but very significant bending stress applied from a pair of coupling nodes near each end. (nut and tuning post, and the front edge of the bridge and the screws that attach the bridge) This stress makes the neck act like a beam with the weakest point again near the nut. So, if the thing fails it will probably break the headstock off.

Now, in a neck through, things are a lot more complicated to analyse because of the neck joint. There are too many variables and details in how the thing is constructed. The greater axial stress is (usually) handled entirely by the butt of the neck heel against the edge of the pocket. The bending stress is dependent on the wood fibers between the screw threads, the screws themselves and the distance and layout of the patten of the screws. The total stress will be divided by the number of screws with the greatest amount at either end of the pattern. Any middle screws will receive a lot less of that stress unless any excessive tightening is done there.

What this means to "punch" is anyone's guess. There's just way too many variables in play, but I do know that the stiffer overall the instrument is between the nut and bridge the brighter and richer the sound. The weakest point of the structure will have the greatest impact on tone. But, if done properly, a bolt on can be just as strong as a neck through.

There are many problems with this analysis.

 

[lowendfriend]

The genesis of bolt-on is purely cost....easier to manufacture....easier to find uniform material for a "neck only" than for "headstock to bridge". Labor....material= cost.

I suspect the difference is similar to having perfect string intonation vs. being a few cents "off".

An NT is one long piece with (presumably) uniform properties along its whole length. I suspect this is where the "more sustain" argument comes from. This would be especially believable if the resonant frequency of the neckthru piece was compatible with the range of strings, so that the vibration of the wood does not destructively interfere with the string vibrations. I think that would mean I'd want the neckthru piece to have a high resonant frequency (very stiff in other words.)

A BO has two different materials and a big discontinuous joint in the middle somewhere. If both materials (neck and body) have high resonant frequencies and the bolt-on joint doesn't disrupt that, then they'd be hard to tell apart from a NT.

Just trying to think it through in physical terms....

 

[Nev375]

There are many problems with this analysis.

Okay. Too many to comment on?

I admit it's been 20 years since college and my terminology might not be perfect, but I'm curious to see where you think I screwed the proverbial pooch on it.

 

[Blue]

The bolt on (screw on, actually) neck joints on Fender are to make servicing easy.

Twenty nickels sez the bolt-on / screw-on neck joints were developed by Leo exclusively as a way to cost production costs.

 

[ON the ONE]

We've got scientists and engineers in here so I would like to ask.... If we put sustain and tone on hold for a second, would someone please elaborate on what effect neck const. has on dead spots. I used to play Warwick basses. I had a NT $$ and a sub had the exact bass but BO ( diff. woods). Not the same instrument at all!

 

[Coolhandjjl]

does anybody have a copy of American Lutherie #91, from 2007 lying around? Apparently there's an article in it touching on the subject.

Lutherie Myth/Science: Neck Joint Type and Sustain

I guess no one read it. From the article:

The initial premise: Neck through construction is considered to offer the best sustain, followed by set neck construction. Bolt-on necks are considered to offer the worst sustain. A recent experiment in this area suggests that this order may be backwards and that folks can't hear the difference in sustain based on neck joint type anyway.

A recent study performed power analysis, spectrographic analysis, and listening evaluation on a series of purpose-built instruments. The study was based on only a small population of instruments but it was reasonably well controlled. The power analysis results suggest that the relationship between sustain and neck joint type is the reverse of the conventional wisdom on the subject. Longest sustain was associated with bolt-on necks and shortest sustain with neck through construction

But then they go on to state: Although limited in scope, this study does suggest that correlation between sustain and neck joint type may not be of practical significance.

 

[Actium]

Physics aside I enjoy how neck through guitars and basses look. They just look...whole. My guitar is a bc rich neck through and it just looks nice from the back side.

I have heard stories about how if you bend the neck slightly to get that pitch bend that it damages neck throughs more easily.

 

[pie_man_25]

I guess no one read it. From the article:

The initial premise: Neck through construction is considered to offer the best sustain, followed by set neck construction. Bolt-on necks are considered to offer the worst sustain. A recent experiment in this area suggests that this order may be backwards and that folks can't hear the difference in sustain based on neck joint type anyway.

A recent study performed power analysis, spectrographic analysis, and listening evaluation on a series of purpose-built instruments. The study was based on only a small population of instruments but it was reasonably well controlled. The power analysis results suggest that the relationship between sustain and neck joint type is the reverse of the conventional wisdom on the subject. Longest sustain was associated with bolt-on necks and shortest sustain with neck through construction

But then they go on to state: Although limited in scope, this study does suggest that correlation between sustain and neck joint type may not be of practical significance.

yeah, I'd really like to read the whole article. I'm starting to think that subscribing to the GAL would be very beneficial to me, even though I have no plans on becoming a pro.

 

[denchiq]

I used to favor neck-through basses. I literally felt they gave me the sustain. Later I got my hands on the Lakland 4-94 and 55-94. It has a bolt-on neck and still has sustain for days. I can leave a note between the songs and it won't cease nor it will it go down into feedback, just sing approximately at the same volume.
Another point was in the access to the upper frets. Not that I am a shredder, although I would like to be one. It just gives me the feel that I have an extra that I might need some time. Then again, the 22 fret Lakland offers a WAY better access to the 22nd fret than the 2-octave necks of the Ibanez SR 905 and B.C.Rich Warlock I had had.
So now I think, much of it is in the construction.

 

[pilotjones]

Okay. Too many to comment on?

I admit it's been 20 years since college and my terminology might not be perfect, but I'm curious to see where you think I screwed the proverbial pooch on it.

Okay, sure.

Problem is that a laminated beam runs the full length beyond the nodes where stress is induced, a neck joint on a bass does not,

OK

making things inherently weaker. (typically)

Disagree. The jointed can easily have greater strength than the surrounding area. In shaft fatigue cases, this bin fact becomes a problem due to stress concentrations just beyond the joint area.

In comparing the neck through, almost all the stress is applied axially, so for that stress, the neck acts like a column with the weakest point being the area of thinnest cross section. (near the nut)

True. But, I should mention that the analysis here has been about strength, which is not the proper object of analysis if we are considering the tone of neck-thru versus bolt-on; either design provides strength far exceeding that required to prevent failure under string-induced loading conditions.

However, since the force is applied from one side rather than the absolute ends, there is a small, but very significant bending stress applied from a pair of coupling nodes near each end. (nut and tuning post, and the front edge of the bridge and the screws that attach the bridge)

Yes

This stress makes the neck act like a beam with the weakest point again near the nut.

yes, but again, so what? no direct bearing on sustain or transient response of NT vs. BO

So, if the thing fails it will probably break the headstock off.

Empirically true only of necks with angled headstock and no scarf joint, resulting in short grain which, combined with the extreme anisotropy of wood, encourage a break. Other headstock joints (flat, angled scarfed) are not commonly affected by this problem. And again, no bearing on sustain of NT vs. BO.

Now, in a neck through, things are a lot more complicated to analyse because of the neck joint.

Disagree. The "joint" area, as complicated as it may be, is far simpler than the joint area of a BO. It consists of a profile thinning, followed (as we progress into the body) of the abrupt addition of body wings, with the core area maintaining the same wood properties as the neck shaft, less the fretboard of course.

By contrast, in a BO there is the highly complex transition area of two overlapping pieces of wood, brought into compression by metallic screws. These two woods nearly always have different properties. Then one of the two pies of wood abruptly flares out into a body, continuing that same, different wood from the neck shaft.

Here one would postulate that there could be a real difference in vibration transfer between the two. In the NT, while the body width suddenly pops up, the wood fibers are both non-changing in their nature, and continuous (uninterrupted), which is all the more significant because the speed of sound is around three times as fast longitudinally with the tree growth direction as it it is radially or tangentially. By contrast, vibrations in the BO joint are forced to travel through radial or tangential direction, and are further subjected to a differing woods boundary, which would partially act as a node of reflection and wavelength change, just happens with light at a boundary with differing indices of refraction.

There are too many variables and details in how the thing is constructed. The greater axial stress

What stress greater than what other stress?

is (usually) handled entirely by the butt of the neck heel against the edge of the pocket.

Not sure this is true. I've seen gap plenty of times. I think it's more accurate to portray the oint as a typical compression-clamped friction joint. Or perhaps it has characteristics of both types.

The bending stress is dependent on the wood fibers between the screw threads, the screws themselves and the distance and layout of the patten of the screws. The total stress will be divided by the number of screws with the greatest amount at either end of the pattern. Any middle screws will receive a lot less of that stress unless any excessive tightening is done there.

Agreed, but not seeing any direct implication for sustain of NT vs. BO.

What this means to "punch" is anyone's guess. There's just way too many variables in play,

Somewhat agreed, except that if we were first to come to an accepted definition of "punch" then there might be progress in analysis of what physical characteristics could enable it.

but I do know that the stiffer overall the instrument is between the nut and bridge the brighter and richer the sound.

Unfortunately, this is subject to controlled testing that has not to my knowledge been done, confirmation bias, and and wibbly-wobbly definitions of "richness," "brightness," etcetera. Also, no relationship is drawn to "punchiness of NT vs. BO," and so forth.

The weakest point of the structure will have the greatest impact on tone.

Disagree. For example, I put forth that I would expect that if the neck joint included a neck depth by neck width by 6" long steel block, it would likely have a large influence on the tone, despite it being the strongest part of the neck.

But, if done properly, a bolt on can be just as strong as a neck through.

Again, strength is not the issue here. Any neck is strong enough for string loading, not to mention that just about any headstock transition region except angled unscarfed mahogany is strong enough to with stand the additional loading of a drop.

 

[Ric5]

After playing bass for nearly 50 years, I can't give you a definite answer. On several occasions I've even had two identical basses (same materials, electronics, hardware and strings) and they sounded and responded differently.

Yes no 2 pieces of wood are identical.

The main advantage of neck through is you don't hit the heel when you play the upper frets.

The main advantage of a bolt on neck is you can shim the neck to raise it or tilt it. Also you can easily replace the neck.

 

[Matthijs]

The overall strength of construction and resonance are probably of influence on sustain and frequency absorbtion, and the construction method is one of the many aspects involved. What puzzles me about this is:

To my ears that effect is not limited to sustain and eq, there's something else in the overall tone that differs. My theory is this might have something to do with the absorbtion of extra tension. When you pull the string you create a higher tension, which in turn causes a slightly higher pitch for a very short time. A slightly weaker constructed bass will have less of this effect, as it will absorb the higher tension more quickly. The result might be what some call "roundness": a more balanced, friendly tone. This effect, if it exsists, should be measurable.

 

[Ric5]

This bass here has a bolt on neck and it has more sustain than all of my neck through basses. This bass has a really heavy solid maple body that really helps the sustain.

 

[Ric5]

This bass also has great sustain and it is a bolt on.

I thing the extra force of the additional strings increases sustain.

 

[Ric5]

Also I found that when I convert a 4 string 4003 to a 5 string it really improves the sustain on the E string of that bass. No weak E string on this bass here.

 

[pilotjones]

I guess no one read it. From the article:
The initial premise: Neck through construction is considered to offer the best sustain, followed by set neck construction. Bolt-on necks are considered to offer the worst sustain. A recent experiment in this area suggests that this order may be backwards and that folks can't hear the difference in sustain based on neck joint type anyway.

A recent study performed power analysis, spectrographic analysis, and listening evaluation on a series of purpose-built instruments. The study was based on only a small population of instruments but it was reasonably well controlled. The power analysis results suggest that the relationship between sustain and neck joint type is the reverse of the conventional wisdom on the subject. Longest sustain was associated with bolt-on necks and shortest sustain with neck through construction

But then they go on to state: Although limited in scope, this study does suggest that correlation between sustain and neck joint type may not be of practical significance.

I greatly respect Mr. Mottola, and love all the good information and good reasoning he presents on his site.

A couple of things here:
1. I wish he had provided the study or a link to it, rather than turning it into an anecdote. Perhaps this wasn't possible, but I'd like to look at the study and be able to analyze its data and conclusions.
2. So much dedends on definitions. While in a study like this you can objectively measure the sustain as the T60​ for the overall power of the vibration, this does not necessarily relate to the the user-justifiable concepts of sustain and punchiness. For example, if my punchy is defined as "having a rapid initial decay of all frequencies," then a punchy bass is less likely to have long sustain. If my punchy is defined as "having a rapid initial decay of the high end, settling down to something primarily bassy," then a punchy bass could easily also have long sustain, as long as my definition of sustain allows for there to be energy in any frequency band,as long as there is some sort of sound. If my punchy is defined as "trebly enough to cut through the drums," then there another, different set of requirements, and lack of requirements.

IOW, trying to speak of desired results in terms of sustain or punchiness in a musically practical sense, is futile unless you first can find what those terms mean with respect to amplitude response and frequency response simultaneously. It requires a 3D concept of frequency and amplitude versus time, not a simple look at "how long does the note last" or "how bright is it."

 

[SolarMan]

So, in summary:

Both can be great ways to construct a bass guitar. Period.

And, the winner is:

Bolt On!

Why?

1) Easier to repair

2) Allows changing of neck without damaging the neck - More versatile - can even swap back and forth on a whim

3) Easier to adjust - shim it, tilt it, etc...

4) -and this one is subjective- It Just Plain Looks Way More Rugged and Manly - as opposed to those dainty looking les paul guitars or such

(no offense intended for the ladies - and there is nothing more sexy than a lady throttling a Bolt On!)

Sorry, can't speculate on the physics - but that is all we seem to have gained from this thread - speculation

YMMV

 

[Rockin Mike]

Electronics matter too.

Any kind of compressor can affect sustain and punch more than differences in neck joint type.

This unsubstantiated opinion has been brought to you by... me.

 

[cnltb]

The main advantage of neck through is you don't hit the heel when you play the upper frets.

that depends entirely on how the specific bass has been designed.
On my bolt neck bass I have no such problem.

 

[MostlyBass]

I'm on my 6th electric bass and it's my first neck through. My observations are that this bass has the most sustain I've ever experience and playing up high where the joint would be is awesome.... HOWEVER, this is also the most expensive bass I've ever owned so perhaps all comparisons are null and void.