Body Shape Tone Theory

[Mickguard]

I came across this quote today--a guy discussing the tonal differences from the shape of a guitar...seems kind of fishy to me...since I'm cutting up a Telecaster body, it'll be interesting to see what kind of tonal change I get...What do you all think?

"My research showed that the difference between Gibson- and Fender-style guitars mainly lies in the dimensions of the guitar's "waist", the indentation between the upper and lower bouts. If a guitar is "offset" like a stratocaster, with the left side upper bout overhanging the right because the indentation is wider on that side, the guitar will have a it's primary voice in the treble. It will be "twangy", or if distortion is used, "thrashy" (an Ibanez is just a strat with a humbucker and gets its fat mids from its electronics). If the waist is symmetrical, the guitar will speak from the midrange with a vocal "aw" sound, like a Les Paul. The bass and mids resonate in the lower bout while the treble resonates in the upper, so the more freely-vibrating wood there is in the upper bout, the brighter the tone will be. Therefore, a double cutaway guitar will be brighter than a single-cutaway (assuming that more wood is added to the "horns" than if they just made it a cutaway by removing wood). This explains why Les Pauls tend to be bottom-heavy. The left-side upper bout is "complete", locking the wood in place and preventing it from vibrating as freely as it would if it were scooped out. NOTE: Any guitar can be made to have fat mids with a combination of pickups, EQ and FX. That doesn't mean the guitar's *voice* is in the midrange."

[erikbojerik]

Any bit of wood will vibrate with a fundamental frequency (vibrations per second, or Hz) that is directly related to its volume (LxWxH). This fundamental frequency is usually referred to as the 'resonant frequency' because the wood resonates most strongly at that frequency. It is easily demonstrated (most easily with acoustics); plug into an electronic tuner, mute the strings, hold the guitar by the headstock, then tap the guitar body, you'll usually register the same note (maybe detuned D#...?) every time you tap.

With acoustic bodies, the resonant frequency is related to the volume of air inside the entire body. With solid body electrics, it mainly a combination of the size of the largest bout on the body and the wood type.

The guy is basically saying that a strat will have a higher resonant frequency than the LP because its lower bout is smaller in volume (he is also considering the part of the body above the waist to be a second resonating piece of wood, but the two bouts are not independent of each other). But body size is only part of the story; wood type also makes a big difference. In solid bodies, wood type is probably more important than the body dimensions in determining the guitars voice. My mahogany+maple travel guitar sounds very similar to my mahogany+maple Les Paul Custom, even though the body dimensions are radically different. The difference that I do hear is probably a combination of the body size & pickups.

[KTLguitars]

It is actually the weight (Density) combined with the stiffness (Modulus of Elasticity) of a certain body that decides its resonant freequency or Main Voicing as it will be in an instrument. In addition to this all materials has an internal dampening effect, actually deciding the richness and distribution of the freequency spectra from instruments.

The main factors separating Les Pauls from Fenders (acoustically) are the material choise and the total weight difference in addition to the set neck versus bolt-on and Fenders longer scale.

The shape diffence of the two doesn't influence the sound much compared to the above mentioned factors.

[Dugz Ink]

I would be willing to bet that, if you suspended a guitar body in the air without hanging it from the horns (ie: put 1 bolt in the middle of the back of the body), you would be able to measure variations in the vibrations of the center of the body versus the wings versus the horns, and so on... if you had some really precise monitoring equipment.

However, once the upper horn becomes a weight bearing arm, then it's ability to "resonate" should be severly limited... thus limiting the potential positive effect that it can have on the guitar body's resonance.

All of that is true, unless the horn(s) is of such a length/width/thickness that it would resonate at a non-harmonic rate to the rest of the body; in that case, an appendage would actually decrease the total resonance.

That's the reason that mis-matched lengths are used to decrease wind generated harmonics in broadcast antenna towers; if two lengths are vibrating at non-compatable frequencies, then they mute each other. Of course, we're not talking about a guitar horn that is 28" wide and 300' tall, and it's also not made out of hardened steel, so any effect (positive or negative) will be relatively miniscule.

Will it have some level of affect? Yes.

Will you be able to hear that affect? That's debateable.

Will it have as much affect as wood quality? No.

Of course, somebody is likely to have a different opinion. They may even think that I don't know anything about wood, vibrations, physics, and/or music. So don't go around quoting me.

D~s

[westhemann]

i think all these theories distract from the real important parts of building a custom guitar.

i think you should build whatever shape guitar you feel most comfortable playing,use nice straight grained pieces of wood,pick out the electronics you feel best compliment your playing style,and choose good quality hardware.

shape be damned...if you build it with tight tolerances and good parts...you WILL like the tone you get...and if you get a hair too much treble or too much of a "whoomp" in your bass...i bet you will use your eq to tweak it out...or change out the pickups to compliment the unique tone of the instrument you built.

by the way...les pauls are bottom heavy because they use mahogany in the body AND neck.the maple cap and ebony fretboard are there to add some snap to all that "oomph"

[KTLguitars]

Westhemann, I agree with you about diciding the shape out of aesthetic reasons more than acoustic for a solid body guitar, most because the shape doesn't do much for the sound, and the neck is actually the "softest" part of the construction (even with truss-rod and carbon reinforcements).

In a solid body guitar the most prominent natural freequencies are normally decided by the mass of the body (wood dencity and volume) and the stiffness of the neck (shape and the modulus of elasticity of the wood) and then the quality of the joint between them. These freequencies is normally relatively low (a few hundred Hz) and is also harder to dampen out the lower they are (heavy body - soft neck). They are easier to handle with e.g pick-up changes if they are higher.

A heavy body (for increased sustain) is easier to handle with a stiff neck wood/construction to avoid problems with powerful natural freequencies.

After this the choise of wood gives other tonal qualities regarding the distribution of the higher freequecy spectra.

In addition to the aestetics, I normally use the shape to determine the position of the center of gravity, giving the guitar the same balance caracteristics both when hanging on a strap and sitting down.

[darren wilson]

Unless the "research" involved making identical guitars using the same materials, construction methods, scale length and electronics, i can't see how anyone could point to a feature such as the width of the guitar's 'waist' as any kind of scientific conclusion.

Doing proper scientific research is all about controlling variables. Even in analyzing only the body shape, you'd pretty much have to make the guitars out of carefully controlled synthetic materials, as we all know that the tonal quality of woods can vary from board to board, even if they came from the same tree.

The main factors separating the acoustic tones of Les Pauls from Strats and Teles are not only woods and the neck attachment methods, but also the scale length.

[MzI]

If im not mistaken Gibson did some research during the mid to late 50s. Basically there research resulted in body shape does not matter. Three guitars came out of it Flying V, Explorer, and the ever elusive Modern. Me personally, I love my Flying Vs and they sound awesome. You can give me all that tonal mumbojumbo and im gonna keep playing em.

MzI

[G_urr_A]

"an Ibanez is just a strat with a humbucker"

I didn't read all of this thread. I just thought I'd post one little comment.

The part quoted above is what made me loose respect for these theories.

To the best of my knowledge, the tonal differences that shape will give you are rather small. To consider an Ibanez (presumably and RG, but he didn't say) to be "just a strat with a humbucker" when dealing with so small tonal differences seems rather (please excuse my lack of vocabulary) dumb.

It's a bit like saying that planes with aluminium seats fly better than others and also state that a Cessna 182 is pretty much a Boeing 747 minus the bulge in the nose...

[westhemann]

Me personally, I love my Flying Vs

the world's most perfect guitar style.....so easy to play(if you are a stand up player) and so good looking.

[Kevan]

I came across this quote today-......."

This coming from a site where their "Best Value Guitar Buy" averaged just under $2300.

Forget the grain of salt. Consider investing in Morton's.

The internet has created way too many 'experts'. You'll find many of them on the HC boards.

Avoid the "experts on HC" and just print out what KTL said.

[Mickguard]

I came across this quote today-......."

The internet has created way too many 'experts'. You'll find many of them on the HC boards.

I hear ya. I just thought it was an interesting bit of mumbo-jumbo to put up here....

I mean, if there's any difference in tone, it has to be extremely small...but that's where snobs like to live, eh?

[frank falbo]

Just remember to pass everything through this test: "Does it change the way the string vibrates, and therefore change the way the pickup senses the vibrations? If so, to what degree?"

This body shape deal is old and stupid. Yes, to a certain degree you need a nice sized mass. So a steinberger or chiquita sized guitar will have a different tone than a full sized guitar of the same material. You also need a good amount of wood around the neck joint, so an SG or a V might be a little different in the way the neck vibrates in relation to the body. But otherwise its a load of crap.

When you plug in and play, you aren't measuring the acoustic properties of the guitar. I mean you can have a hollowbody that reacts acoustically to the amp, so acoustic properties aren't totally invalid. But for a solidbody, most (if not all) of what you're hearing comes from that main teardrop-shaped inner mass between the neck and the lower bout. Your two points of vibration transfer are the bridge and the neck joint. So follow your vibrational pattern out in a circle from those two points and you'll have your degree of effect. Then realize that the bridge's effect on body vibration is weighted more heavily, probably by a 3:1 ratio to the neck joint, and so long as you build something with a good teardrop shaped mass inside it you can throw the rest of this discussion out to the recycle bin, along with your Harmony Central bookmark.

[erikbojerik]

Not quite...I am actually in the early stages of trying to measure the frequency response of different tonewoods. OK, I'm starting with pine (not quite a tonewood), but my first experiments show that reducing the volume of the body actually changes the resonant frequency (as you would expect from first principles).

You do this by taking a single piece of wood and cut away at it, measuring the response as you go. That way everything else (density, moduli, etc) stays constant and only the wood volume changes.

Once I can translate the audio files into reasonable spectra that make sense, I'll post the results.

[darren wilson]

erik: By reducing the volume, you're also reducing the mass, which is a different argument from the shape one. If you start with two identical blocks of material with the same resonant frequencies, then you carve one down to a "V" shape and the other down to a Tele shape, with the same mass leftover, i highly doubt one is going to sound perceptibly different from the other.

[KTLguitars]

To sort this out once for all...

erikbojerik:

Not too fast with what stays constant:

The mass increases linear to increase in volume but the opposition to bending (stiffness) increases by a factor square root of 2 (=1.41) -for a quadratic cross section. Stiffness is dependent of the section modulus - which also is dependent of the shape of the object - see this page for a reference Section Modulus.

So here we are - yes there will be a change in tonal characteristics when the shape is altered BUT compared to other factors mentionned in several posts above (neck and neck joint, wood types, bridge type, etc) the shape will be insignificant for the instruments total characteristics -as long as the shape changes are small like from Les Paul to Strat - a flying V is a more dramatic change and will certainly make some (still minor) difference.

However, the thickness of the body has a significant influence, as the first natural mode of vibration of the body is the deflection from front to back (See the .gif animation of the response of my Magnum648 here).

An increase of the body thickness from 1-1/2" to 2-1/8", 1.41 times, doubles the stiffness but increases the mass only with a factor of 1.41. As the bending momentum is largest in the middle of an object, increasing the thickness here will increase this weight/mass ratio even more (as you avoid adding mass in the periferi but still increases the stiffness) This gives you the arch top guitar - and a further explanation of the body differences of Les Pauls and Strats.

I am sorry about my explanations - English is not my language - but I hope this can help sorting out what really happens - and what is only technical superstition! As I am fairly interested in this subject I am exploring it as a hobby - not a need for my guitar building - Don't be too scientific - it is your feeling that creates the instrument - but knowledge never hurts. I do calculations on my designs just to avoid any major blunders when working with combinations of different materials and special shapes - but when it comes to the building, nothing can substitute the human experience and ear in the decision of shape and selection of wood when it comes to acoustic qualities!

[erikbojerik]

I agree with everything you've said KTL; mainly you're speaking from the perspective of mass while I spoke from the perspective of volume (to analogize with acoustic guitar bodies). Of course they are the same thing for a given density.

At this early stage I am mainly concerned with measuring the frequency response of different wood species, while keeping track of the intensive (or conservative) variables along the way (density, moduli, etc); stiffness in not an intensive property. I'm doing only S4S planks, as it is easy to make them all the same size (volume). But first I'm trying (A) a single plank as a function of volume (mass), and ( multiple planks of the same species. It is a long-term spare-time kinda project. Hopefully, in the end I'll have intuitive frequency response spectra that will quantify the EQ in the "tone" that we recognize from different tonewoods (because one man's midrange is another man's mud).

[thedoctor]

KTL has it nailed but I would like to offer an analogy to maybe muddy the waters. I love muddy waters. If a guitar were a drum, the bridge would be most effective in the center, right? Dear god in heaven, I just described a banjo! Shame, shame. Well, guitars aren't banjos. Ignoring the neck for the moment, guitar bodies recieve most of their energy from the bridge. The vibrational length, frequency, would be the distance from the bridge to where the stiffness (MOE) transferes enough energy to overcome inertia (mass/density) in a given direction. This theory would say that regardless of stiffness and density OF the wood, as many possible different lengths from bridge to edge should be the best for all around flat freq. response. More bridge to edge lenghts of the same length should fatten that particular freq. Also means the best resonance would be had from a body made from a crosscut slab with the bridge right at the heartwood center. Now there is an ugly thought! Maybe a solid body with 1/2" thickness at the bridge tapering out to 2" at various distances away from the bridge. Not a pretty sight. If you could vary density as it approaches the edge? Like an old fashioned flywheel made offcenter? Another Kodak moment. I'm done , finally.

Plese don't take me seriously.

[Reaper]

It would seem to me that the original poster (on HC) is attempting to seem smarter than he really is.