I am a physicist building a Guqin, an old Chinese zither. I try to understand its construction, how it vibrates, what are the key features to obtain a good sound.

Wikipedia's image of Guqin

I found only one paper on the subject, Vibroacoustic of the Guqin, but it is only scratching the surface. Can somebody with playing / building experience give me suggestions? More specifically, I am trying to understand:

  1. What is the main drive mechanism? In guitars and violins we have the strings attached to a light bridge and thin soundboard, while for the guqin the head is massive! How is the vibration of the strings transmitted to the body?
  2. Are there some "cheap tricks" to change its sound, like closing the soundholes, that can help understand what affects the sound?
  3. Tonewood choice. I am now using Larch as the main wood material, because of its availability, and I like the color. Officially, I should use Pawlonia wood that is much lighter, but I can't find it here. I have seen an instrument for sale made of Fir wood. Is there a difference?
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    I doubt a player would be able to answer that better than you. You may have to dissect one carefully, or mount some accelerators to the device and take some measurements. As a physicist how familiar are you with musical acoustics? You might benefit from looking at the texts by Fletcher and Rossing on instrument construction (though mostly Western). At the very least you may find more articles in the reference sections, or be able to do a search for new papers that cite Fletcher and Rossing as they are the well known.
    – user50691
    May 6, 2019 at 13:03
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    There's a lot of black magic involved in producing any acoustic stringed instrument. There's also a lot of math - I've seen the sketches and equations a local luthier uses when designing the dimensions of a violin body. The type and quality of wood uses has a small effect, but you won't know until you've built a few. That said, since it is in the zither family, try researching zither fabrication in general. May 6, 2019 at 13:35
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    There's some background information here: guqinreflections.com/making-a-qin-design-considerations For instance, it says the traditional top wood has the highest strength to weight ratio of any wood. A very high strength to weight ratio is also a hallmark of spruce, which is why it is popular for guitar tops. That suggests the top wood is meant to be sensitive to picking up and amplifying the vibration of the strings. High strength and low weight means it may be carved thin to make it have as little mass as possible, therefore less inertia and therefore easier to set into motion. May 7, 2019 at 1:19
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    The vibration is still transferred to the body through the bridge. Just because the bridge is massive doesn't mean it won't transfer energy. A bridge with more mass will have two effects: 1) It will damp higher frequencies more than lower ones, so it will make the tone less bright, and 2) it will increase sustain, because more energy will be reflected back into the string instead of transferred to the top. May 7, 2019 at 1:21

1 Answer 1

  1. The string vibrations are transferred at the point where they contact the body, like all other stringed instruments. As one commentator pointed out (and I concur from personal experience) the sustain will be improved by higher density wood, and/or more mass at the contact point. The nut on the left (photo) seems to resemble a guitar nut, so I would recommend graphite for improved intonation and playability (allows the strings to slip and vibrate easily).

  2. Everything you change will affect the sound in some way. Closing a sound hole will definitely make a noticeable difference. Take any acoustic guitar and cover the sound hole to hear an example. The string vibrations echo and resonate in the body chamber (and throughout the instrument) and emerge amplified from the sound hole. If you plug the hole, it will be quieter (less projection). Additionally, if there is a soundboard, touching it or dampening it will also have a big impact.

  3. Wood has a major impact on the sound of an acoustic instrument, not a small impact. If you want something lightweight, try Chinese Basswood (aka Linden). It is light, easy to work with, flexible, and very affordable (which is why so many modern guitars are made from it). It is also widely available.

  • Thanks for the contribution! Yes on the left it's a nut, graphite may be a nice try. The tuning pegs are actually under the bridge on the right (the bridge may then be coated with graphite). In the meanwhile I built the instrument out of larch (no graphite, ebony nut). The basswood idea is nice, it's a bit on the heavy side, but if i can get good large planks it may be ok
    – patta
    Nov 7, 2019 at 16:03
  • @patta Basswood is NOT "a bit on the heavy side" ... it is widely known as being light and comparable to Ash. Swamp Ash was famously used for Fender guitars for many years due to it's light weight and low density. Basswood is now used. Ebony is great for fingerboards because the extreme hardness reflects [notes] well, but I would not recommend it as a nut. The slipperiness of graphite is ideal for a nut (or bridge) because the strings need to be able to slide easily. I didn't comment on the tuning pegs but thanks I guess for confirming what the photo shows. Reminds me of Steinberger's design. Nov 18, 2019 at 5:15

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