String inharmonicity vs material

[smart51]

I've been reading up on string inharmonicity. It seems the problem is related to the stiffness of the material the string is made from. Which made me wonder, is one material better than another for this?

From what I've read, the pitch of the each overtone comes from the sum of 2 tensions - the tension due to winding up the machine head, plus the tension needed to bend the string. The 1st overtone bends the string in a single arc from bridge to fret. The second overtone has 2 bends, bridge to half way and half way to fret. The third overtone has 3 bends and so on. So higher harmonics have higher total tension and tend to be a bit sharp.

A flexible string has low bending tension because it is flexible. Higher harmonics are pretty much in tune with the fundamental. A stiff string needs a lot of bending force so the higher harmonics are out of tune.

So lets say you have a drop tuned 4 string, or a short scale 5 string that suffers from inharmonicity. Would changing the material the string is made from help?

Steel strings with nickel plating have a Young's Modulus of 210 GPa (give or take)
Solid Nickel has a Youngs Modulus of 190 GPa.
Stainless Steel has a Youngs Modulus of 180 GPa or so depending on the grade.

Now lots of things affect this. Core size, over all size, winding type and so on. But in theory, stainless steel strings should have less harmonicity. Have any of you noticed whether string material makes a noticable difference?

 

[Skerrvydog]

interesting topic but way over my head without doing the background research that you have done. Would you be able to summarize?
Have you come to any conclusions?

 

[michael_t]

interesting topic but way over my head...

+1

 

[Gsnorgathon]

I have to guess there's all sorts of stuff that might go on at the nanoscale to affect the flexibility of materials used to make strings. But I also guess that the mechanical properties resulting from how the strings are manufactured have a bigger effect. It's an interesting topic!

 

[iiipopes]

Have you considered contacting Dr. Kemp at St. Andrew's University, Scotland, about this? Here is the thread on his inharmonicity research:
Physicists develop bass string theory

 

[smart51]

Have you considered contacting Dr. Kemp at St. Andrew's University, Scotland, about this? Here is the thread on his inharmonicity research:
Physicists develop bass string theory

He made me a 5 string set of his lumped strings in short scale. The B was too long and it snapped trying to wrap it round the tuning peg. He's going to make me a replacement that's a bit shorter. We'll wait and see what difference it makes.

 

[iiipopes]

He made me a 5 string set of his lumped strings in short scale. The B was too long and it snapped trying to wrap it round the tuning peg. He's going to make me a replacement that's a bit shorter. We'll wait and see what difference it makes.

Did you see where he quoted my post when after I read his article, I tried his solution using a small piece of golfer's lead tape? Granted, it was on a short-scale 4-string, not a 5-string, but what I did notice is the damping of the inharmonicity and the positive effect gets better going from the G-string to the E-string. I extrapolate that it will help the B-string even more. As I posted then, what I noticed is that in addition to damping the inharmonicity, it does damp some of the highest overtones as well on my experiment. Your strings, with the round wound treatment instead of a small bit of tape, may not. I am interested for you to post how your strings sound overall in tone compared to conventional round wounds.

 

[Petethebassman]

Core type is IMO crucial- I prefer round core strings as they're usually more flexible than hex core. TI Jazz Flats and Pyramid Gold flats are both round core and I use both on my basses. Core-to-wrap ratio has also a significant effect on flexibility and how in tune the overtones are. Strings with stiff hex cores are tough to intonate as the overtones sound sharp.

 

[iiipopes]

Core type is IMO crucial- I prefer round core strings as they're usually more flexible than hex core. TI Jazz Flats and Pyramid Gold flats are both round core and I use both on my basses. Core-to-wrap ratio has also a significant effect on flexibility and how in tune the overtones are. Strings with stiff hex cores are tough to intonate as the overtones sound sharp.

Indeed. And require more offset at the bridge for compensation.

 

[ixlramp]

Material stiffness of the core wire will affect string stiffness more than material stiffness of the wrap wire, because it is easier to bend a helix. All string types probably use a similar optimal steel for the core. Nickelplated / pure nickel / stainless steel only refers to the wrap wire.

 

[smart51]

The Kemp strings arrived today. I'm impressed. Inharmonicity is much improved over the short scale DR sunbeams they replaced, which were better than the Pyramid short scales that I tried first. The B string at the 12th fret still has a bit of a bell like tone, but it isn't as much as my long scale 5 with Ernie Ball slinkies, which I think is great. They're not cheap at £85. More than twice the price of a normal set, but they are better.

As well as the tone, they have a little more tension than the DRs. Not loads, but a bit more. With a .146 guage B string, you'd expect that.

 

[micguy]

The whole point of putting windings on a string is to reduce the dispersive nature of the string - the term we use in Physics (I studied Acoustical Physics in school - I know this stuff) to describe a medium where the speed of propagation depends int its frequency. This has been know in some fashion for hundreds of years - take a look inside a piano, you'll see wound strings - which are usually a copper alloy on a steel core.

Steel gets the nod for cores for a few reasons: First you want a material that won't stretch - a copper string core would never stay in tune. You also don't want a material that fatigues - aluminum strings would eventually fail. Steel is also magnetic (which helps in an instrument with magnetic pickups), and it's relatively cheap.

So, if you make the core out of steel , then it's a matter of its diameter that you get to choose. The core takes all the tension of a string - its purpose is to handle that part of the situation. If you know the tension that the string will be under, then you can size it a bit larger than absolutely necessary (for some margin) - if someone tunes the string bit sharp (a semitone adds 12 percent tension), you don't want the thing snapping. You also want some margin for things like a bit of rust, which will weaken the core over time. The material that windings are made out of are chosen for a few things:

1) Magnetic properties - more ferromagnetic metal makes a bass louder. Copper, while it's heavier (which is good for a winding material - the major point of a winding is just to add mass to the string) isn't ferromagnetic. Nickel is, normal steel (what most of a nickel plated winding is made of) is ferromagnetic, stainless - well, how magnetic it is depends on the alloy.

2) Damping properties - the material and its geometry both play a part in damping. Flatwounds have a ribbon of wire with a lot of surface area touching the core. Roundwounds, not as much - they have less damping (more sustain, more harmonics).

3) How long it holds up in the environment - the nickel plating on steel windings is there in part to slow down the rust you'd get without it.

Anyway, yes, dispersion/inharmonicity is an issue in making strings, but..there are a lot of other factors at play. Most guitarists, in the past, used to use wound G strings, but now most use plain G strings. Those are clearly worse for keeping harmonics in tune, but longevity trumps that concern in the practical world for most folks nowadays.

 

[iiipopes]

The whole point of putting windings on a string is to reduce the dispersive nature of the string - the term we use in Physics (I studied Acoustical Physics in school - I know this stuff) to describe a medium where the speed of propagation depends int its frequency. This has been know in some fashion for hundreds of years - take a look inside a piano, you'll see wound strings - which are usually a copper alloy on a steel core.

Steel gets the nod for cores for a few reasons: First you want a material that won't stretch - a copper string core would never stay in tune. You also don't want a material that fatigues - aluminum strings would eventually fail. Steel is also magnetic (which helps in an instrument with magnetic pickups), and it's relatively cheap.

So, if you make the core out of steel , then it's a matter of its diameter that you get to choose. The core takes all the tension of a string - its purpose is to handle that part of the situation. If you know the tension that the string will be under, then you can size it a bit larger than absolutely necessary (for some margin) - if someone tunes the string bit sharp (a semitone adds 12 percent tension), you don't want the thing snapping. You also want some margin for things like a bit of rust, which will weaken the core over time. The material that windings are made out of are chosen for a few things:

1) Magnetic properties - more ferromagnetic metal makes a bass louder. Copper, while it's heavier (which is good for a winding material - the major point of a winding is just to add mass to the string) isn't ferromagnetic. Nickel is, normal steel (what most of a nickel plated winding is made of) is ferromagnetic, stainless - well, how magnetic it is depends on the alloy.

2) Damping properties - the material and its geometry both play a part in damping. Flatwounds have a ribbon of wire with a lot of surface area touching the core. Roundwounds, not as much - they have less damping (more sustain, more harmonics).

3) How long it holds up in the environment - the nickel plating on steel windings is there in part to slow down the rust you'd get without it.

Anyway, yes, dispersion/inharmonicity is an issue in making strings, but..there are a lot of other factors at play. Most guitarists, in the past, used to use wound G strings, but now most use plain G strings. Those are clearly worse for keeping harmonics in tune, but longevity trumps that concern in the practical world for most folks nowadays.

1) Thanks for using the correct term, "damping," instead of being all wet using the word "dampening."
2) Thanks for the observation concerning wound G strings, which I use on all my guitars for your reasons stated.
3) Yes, many factors go into the making of strings. This thread is focusing on one issue: inharmonicity, and more particularly, Dr. Kemp's research and application of his experiments and findings to this one particular issue. As most of the other reputable string manufacturers have addressed all the other issues mentioned, the discussion of a solution to inharmonicity is only recently (last few years) a topic of discussion for bass guitar strings, starting with observations of string behavior of a taper or bare core string regarding intonation, as well as any tonal changes compared to fully wrapped strings.

 

[HaphAsSard]

Flatwounds have a ribbon of wire with a lot of surface area touching the core.

True for thin, guitar flatwounds: bass strings starting from the G (usually) have one or more intermediate, thin round-section wraps between core and flat ribbon. Orchestral strings also have silk inlays for extra damping (more in sets intended for mainly arco use, less in ones meant for pizzicato).

 

[iiipopes]

The 1st overtone bends the string in a single arc from bridge to fret.

Right thought, wrong nomenclature. This is the fundamental, the entire string vibrating as one unit. Then the string essentially vibrating in half is the first overtone, in thirds the second overtone, etc.

 

[smart51]

Right thought, wrong nomenclature. This is the fundamental, the entire string vibrating as one unit. Then the string essentially vibrating in half is the first overtone, in thirds the second overtone, etc.

Should have said harmonic. My mistake.

 

[Mysteria]

All else being the same, a thicker string will have more inharmonicity than a thinner one. Consider, for example, how much harder it is to bend a straw than to bend a solid string of plastic of the same length and mass as the straw. So one idea I have to minimize inharmonicity is to make the string as thin as possible, for the same tension and mass (and therefore the same pitch and how "tight" the string feels) for a given scale length. To accomplish this, the right materials are critical. Two things are needed: 1) a high tensile strength material for the core, so it can be as thin as possible while maintaining the needed tension; and 2) high density for the wrapping material, to minimize volume (and therefore minimize the cross-sectional diameter of the string) while providing the necessary mass. For background, we know from physics that the length of the vibrating part of the string, and the mass of that section, and the tension of that string, together determine the fundamental frequency of the string.

 

[iiipopes]

All else being the same, a thicker string will have more inharmonicity than a thinner one. Consider, for example, how much harder it is to bend a straw than to bend a solid string of plastic of the same length and mass as the straw. So one idea I have to minimize inharmonicity is to make the string as thin as possible, for the same tension and mass (and therefore the same pitch and how "tight" the string feels) for a given scale length. To accomplish this, the right materials are critical. Two things are needed: 1) a high tensile strength material for the core, so it can be as thin as possible while maintaining the needed tension; and 2) high density for the wrapping material, to minimize volume (and therefore minimize the cross-sectional diameter of the string) while providing the necessary mass. For background, we know from physics that the length of the vibrating part of the string, and the mass of that section, and the tension of that string, together determine the fundamental frequency of the string.

You have just described the GHS Balanced Pure Nickel strings.