What happens when the string tension is to high/to low?
The wrong string tensions can lead to an overload or underload. An underload only results in a loss of sound, while an overload can cause permanent damage to the instrument.
When strings sound somewhat nasal or very metallic, this can be a sign that the instrument is underloaded. This means there is too little pressure on the soundboard. A string with insufficient tension can also feel harder under the fingers when playing. Why? In physical terms, this is caused by the many reflections of vibrations on the bridge, which feed back into the string.
In case of an overload, the instrument reacts immediately, mostly sounding darker and broader. Brilliance and sound colors can reduce considerably, causing the instrument to lose the necessary overtones and a portion of its metallic sound component over time. This leads to a hollow and trumpet-like sound. Overload also reduces the tonal lifespan of the strings, which continues to shorten each time a new set of strings is mounted onto the instrument with the same string tension. In addition, the strings often feel softer under the fingers.
In contrast to underloading, overloading can cause long-term damage to the instrument. There are two different and serious soundboard issues:
- The soundboard can exhibit orthotropic and linear viscoelastic behavior due to the overload. A small overload causes the soundboard to sink, but it can recover again completely, and this behavior can be reversed in the long term.
- The more serious case is an overload exhibiting orthotropic non-linear viscoelastic behavior. Here, the instrument is extremely overloaded, and the soundboard can sink irreversibly.
A solution in both cases would be to temporarily underload the instrument – this can last for up to 6 months. By changing to strings with a lower string tension, the soundboard can recover again and mostly reacquire its shape, allowing the sound to unfold optimally once more. Initially, this often produces a nasal and brighter sound because, as already mentioned, the instrument is now underloaded in this situation. But if the optimal string tension has been selected, this sound phenomenon will pass, the soundboard can reacquire its shape, and the sound can unfold optimally in the long term. Patience is key. However, if you persist in using inappropriate and excessively high string tension, you will continue to damage the instrument’s body.
You would do well to seek the advice of an expert, as each instrument is different and its rehabilitation can be a long journey.