Electric Upright Bass



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

Sinus waves in a string

This animation shows the relation between the circular movement and the waveform when it comes to strings:

animation: speed of sound through the string
Animation: a circular movement drives the string into motion. The ‘string’ is made from cylindrical segments that are coupled by hinges. Notice the sinus shape in the last frame.

Speed of sound

As you can see in the animation, the vertical displacement that is induced by the circular movement of the driver wheel and piston, ‘travels’ through the string from string segment to the next string segment to the next… The speed at which the displacement is carried on from one string segment to the next is the speed the wave travels; the speed of sound. This is not the speed of sound in air, but in the string.

(The brainiacs among you might have noticed that the animation shows the so called ‘first harmonic’. I did this to show the sinus-wave form in the string. It doesn’t matter for the theory though).

So anyway, in the animation above, I used a driver wheel and piston to force the string into motion. The string returns, accellerates, falls to the rest state because gravity pulls on it. So here, the material and mass of the hinged segments is not really* important, because as you know, a light material (low density) falls equally fast as a heavy material (high density).

*)’not really’; a heavier material would indeed put more tension on the string, influencing the speed of sound. But to keep the example simple, the effect of mass can be neglected, for now

Tuning fork A 440Hz
Tuning fork A 440Hz

The relation between speed of sound and frequency

The frequency is the amount of complete swing cycles per second, measured in Hertz (Hz).

So imagine you pluck or strike a string. The displacement, the wave, travels through the string at the speed of sound. It takes time to form a wave over the complete length of the string. If the speed of sound is higher, it takes less time to form a wave, so more waves fit in a second; the frequency is higher.

The frequency is what defines the pitch; it defines if the sound sounds high or low. The material influences the speed of sound and the speed of sound influences this frequency.
Probably the most commonly known frequency is the A of 440Hz, which is the A of a regular tuning fork.

The strings of a bass are (usually) tuned to:
E1 41.20 Hz
A1 58.27 Hz
D2 77.78 Hz
G2 98.00 Hz

Introducing elasticity and mass

The string in the animation did not behave like an elastic spring, it didn’t store and release energy like a spring /string can. The mass wasn’t relevant either.
On basses, strings are elastic. In elastic strings the driving force is provided not by gravity, but by the restoring force after stretching the elastic string. The ‘stretchforce’, the tension, provides the accelleration towards the ‘rest state’ (equilibrium).

Introducing elasticity and mass opens up a Pandora’s box of variables /effects and it gets rather complicated. But let’s start easy by sketching the rough outlines of string design.

The rough outlines of string design in 3 steps

A grand Piano uses different string lengths
A grand Piano uses different string lengths (image source)

1. The length of the string

So you pluck or strike a string, the displacement, the wave travels through the string at the speed of sound. The speed of sound itself is not a variable here but a constant, a property of the string. If the string is longer it takes more time to form a wave over the complete length of the string. This means less waves fit into one second and the frequency will be lower.
It works the other way round also; the whole principle of playing a bass is not to have a seperate string for each note like a harp or piano, but to limit the number of strings and create the other notes by shortening the strings while playing. Shortening a string gives higher notes because if the wave travels at the same speed of sound and it is a shorter way to the ends, it takes less time to form a wave over the whole length; more waves fit in a second and the frequency will be higher; the tone will be higher.

So it’s quite logical that bass strings are longer than for instance violin strings.

I am not sure, but I assume the length of the strings on an acoustic bass is limited to the length we currently know as ‘most popular’ (size 3/4 and 4/4), because of ergonomic reasons; it needs to be playable. As it is now, the finger-stretch of the playing hand is already quite large.

How much longer?
A piano has a tonal range from about 40 to 4000 Hz. If you would use the same string and tension for each note, it would require the strings for the lowest tones to be 100 times longer than the strings for the highest tones. This illustrates that only varying the length isn’t enough; simply taking a thin violin string and making it longer will not do the trick, because you would need a very long string for that.

Machine heads

2. The tension on the string

For the bass to ‘feel right’, it is important that the tension of the strings is the same among all strings, you want the strings to feel equally tight /loose.

If tension of all strings is about the same, and the length is about the same, then how do you get the low tone?

A big mass impedes accelleration
A big mass impedes accelleration (image source)

3. The mass of the string

… Well, add mass!
So again: you pluck or strike a string, the displacement, the wave travels through the string. The force that is introduced by stretching the string, induces the accelleration towards equilibrium.

What happens if you make a thin string heavier by for instance glueing a weight onto it?

The force of the stretched string stays the same, but the mass the force has to move is bigger. This makes the accelleration slower. It’s like riding a bike; accellerating with a big load on the bike will make the accelleration slower if you use the same amount of force.
The string will therefore vibrate slower, which means the tone will sound lower. Just what you want for bass strings!

Core wire with (roundwound) winding
Core wire with (roundwound) winding

The principle of bass string design is usually to take a thin core string under high tension to match the tension of other strings to make it feel ‘right’, and then add a winding that increases the mass.

You might have encounterd this effect of mass on pitch in a less pleasant way; windings of roundwound strings on bass guitars are notorious for accumulating dirt quite easily. This dirt has a mass, so… the effect is that dirt drops the pitch. The response is to tune the string a bit up, increasing its tension beyond the value the string was designed for; dirt in string windings is a common cause of string breakage.

These 3 steps are the rough outlines of string design; the length, the tension and the mass. But a gut string sounds different from a steel string. By varying the properties te designer of a string can influence the sound. So how is the color of the tone influenced? What is color of sound anyway?