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Electric Upright Bass

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Meanwhile, in the kitchen… brewing a new model

I am (and have been) working on a new model, check the article for more details!







Making a Neck

link to: new-model-sneak-preview
A in this article a ‘making of’ photo reportage of the new bass’ headstock. More info on the new model to follow.







Pickup placement on an Acoustic Upright Bass

Pickup placement on an Acoustic Upright BassesWhat choices have to be made when you want to record an acoustic upright bass, and what exactly makes it so difficult to record an acoustic upright bass?


Chladni Patterns

link to: Chladni patterns
In lutherie, Chladni patterns are used to visualise the -often spectacular- deformations of a resonating plate (the article contains explanatory video).



String Choice

link to: string choice
This article is meant to give you insight in string design, so you have more to go on than to judge the string by the color and lettertype of the package

Pages: 1 2 3 4 5

String Choice



Shaping the tone

Gut strings Strongly twisted an polished gut strings for the early Baroque era instruments from Pure Corde in Germany



According to my encyclopedia of musical history, instruments that use strings as their source for sound, have historically had strings made out of natural materials like plant-fibres (primitive cultures), horsehair (Asia), silk (eastern Asia), animal tendons and gut (mesopotamia, meditaranian /egypt).

The meditaranian version is what we know from Baroque instruments. These strings are made from twisted guts that are dried and polished. In the 17th century the first thread wounded strings saw the light, followed by brass, iron and steel windings. Today all kinds of modern materials are used.

twisted

The choice for gut in ‘the old days’ is rather logical; the material is strong yet flexible, durable and available at the butcher’s shop. The diameter of this naturally grown material is not large enough to get the desired properties. By twisting the material, the diameter can be controlled. But that’s not the only thing that happens after twisting…

In nature, spirals and helixes are quite common. From galaxies to snail houses to DNA. A spiral snailhouse is a straight snailhouse where (apparently) one side grows faster than the other (the elegance!). For a twisted gut string this means that the outside is longer than the inside, or in other words, by twisting, the outside is stretched more than the inside.
For engineers, this spells ‘reinforcement’. Reinforcement of the outer layers of the string is actually not an advantage when it comes to bass string design.

string stiffness

The second property introduced by twisting is that a twisted strain is easier to bend.

The illustration shows the effect of ‘carving in’ the sides of a beam; it makes it easier to bend. A twisted strand of gut can essentially also be seen as ‘a carved-in beam’.

Higher flexibility, making it easier to deform the string, is a wanted property for bass strings, because it lowers the tone. So that is why reinforcement of the outer layers is not a good idea when it comes to bass string design, you actually want the outer layer to allow flexibility. But why exactly..?

Let’s dig into the speed of sound a bit further. The speed of sound is not the same in every solid material:

Air at 20°C

Aluminum
Steel
Copper
Ice
Bone (dense)
Silver
Wood
plastic (Polyethene)
cork
Rubber

343 m/s

6320 m/s
5100 m/s
3800 m/s
3280 m/s
3000 m/s
2700 m/s
1500-4000 m/s
920 m/s
500 m/s
60 m/s

You might see a pattern here:

The stiffer materials have a higher speed of sound
The low density materials have a higher speed of sound

Effect of mass on the speed of sound

Aluminum is certainly not as stiff as steel is, but is a lot lighter than steel. That’s why aluminum has a higher speed of sound than steel has. Above I already discussed the relation between mass and frequency; the bicycle loaded with sacks of rice; using the same force to accellerate a higher mass, will make the accelleration slower, so less swingcylces fit inside a second. Giving a string a higher mass will make the pitch drop.

Effect of stiffness on the speed of sound

Beams wih gaps filled up

Let’s imagine we fill up the gaps in the carved-in beam. One with rubber and one with steel.

Stiffness is a measure of how hard or easy it is to stretch or compress (bend) something made of solid material. Steel has a higher stiffness than rubber (no surprise here).
It’s quite straight forward logic that the beam that is filled up with rubber bends easier than the steel one, because rubber is more elastic than steel. The crux is…

it takes more time to compress and decompress rubber than steel

Think of the animation above where the wave is passed from segment to segment; this process of passing from one to the next takes time. But it takes more time if the material is more elastic, because the process of compressing (receiving) and decompressing (passing on) takes up time. This is why the more elastic materials have a lower speed of sound. This is why reinforcing the outer layers of the string is not a good idea when it comes to bass string design.

Effect of mass & stiffness on string design

These two, stiffness and mass (density), have opposite effect on the speed of sound. In lutherie there’s a rule of thumb which is not really correct, but anyway here it goes;

Adding weight has the same effect as decreasing stiffness

This means that making the string heavier, has the same effect as making the string more elastic (= easier to deform); both will result in a lower frequency.

Solid versus winding

So what happens when you do not add winding but simply scale up a solid steel cylinder core wire? Answer: then you increase both stiffness which makes the string sound higher, and you add weight which makes the string sound lower. These effects more or less cancel each other. This is why solid steel cylinders for strings do not work when it comes to bass strings. A winding is added, because a winding adds mass, while the stiffness is only raised a little (‘a little’, when compared to the solid cylinder shape).


Tire
A rubber tire absorbs small vibrations (image source)
Superposition wave

Effect of material stiffness on timbre

Why do more elastic materials have a mellower, less bright sound?
To answer this, let’s get back to the superposition story; higher frequencies have a shorter wavelength, they ‘travel along’ the bigger wave so to say; the high frequencies form the small wrinkles on the big wave.
You can imagine that if you have that beam where the gaps are filled with rubber, these very small vibrations are simply getting absorbed by the rubber, they are not passed on to the next segment. The energy of the smallest vibration is ‘lost’ to internal friction.

We use this principle elsewhere also; the rubber tires on wheels do not pass on the small vibrations of a gravel road.

Effect of material stiffness on ‘decay + release’

I don’t know the official name for ‘the time it takes for a tone to die out’. Many call it sustain, but I don’t think that is correct; what would they call a string that is bowed and therefore ‘sustained’? There are many different protocols /envelope types, to me the most logical and correct term for ‘the time it takes for a tone to die out’ would be ‘decay + release’. But anyway…

Material stiffness effects this. If again we take the rubber example. The wave that travels through the string passes on a wave from segment to segment. The wave travels through the string while the segments compress and decompress. During these compressions and decompressions, energy is lost through friction. If the material is more flexible, it compresses further, and so there’s more material compressing, so there’s also more internal friction in the string. The energy you put in by plucking a string will therefore be lost sooner; the time it takes for all energy to be ‘used up’ is shorter, and so we can conclude that vibrations in strings made out of more elastic materials not only sound less bright, the tone dies out faster also.

Stiffness as a property of shape.

As illustrated in the picture of the beams with the weight on it, stiffness is not only a property of the material, but also a property of the shape. The beams that are ‘carved in’ are less stiff, they bend more easily while the force acting on them is the same. And this is a desired property for bass strings, because more flexibility is good for making strings bass strings.
But there’s also another reason why this shape flexibility is a good thing; it allows making a flexible shape out of materials that are stiff, but the loss of energy on internal friction occurs at a lower rate. Because there is less material that compresses, it is the shape that allows the deformation.

And to make it even better, you can choose materials that have a very high density (a high mass for their volume, like wolfram for instance) and have even less material that is compressing and decompressing; even a lower rate of energy loss. The big advantage here, is that these strings are also thinner. And thinner strings are… more flexible.
Not only are they more flexible, the compression and decompression of the outside of the string is smaller. This also means a lower rate of energy loss. All pieces of the puzzle to fit toghether now.

There’s one issue left; the endpoints