In my previous post, I dove into a rather lengthy introduction to alternative wood choices for qin woods, including data from The Wood Database on numerous possible choices for the top and bottom boards, as well as some of my thoughts and experiences using several of these woods for instrument making in general. Wood selection does have a major impact on the overall sound of a qin, and can determine a lot of factors about its visual and tonal qualities. While wood selection is not the only factor determining tone and quality, it certainly can provide the basis for the starting point for designing the qin tone. This post is going to go into a bit more detail on an interesting topic relating to and touched upon in several of my previous posts, in designing for tone when making a qin. However, this certainly does not just apply to the qin, and the same basic principles can be applied to any instrument you are planning on making.
I think first and foremost when aiming for a particular design to achieve a certain tonal quality is actually knowing what it is exactly you are aiming for. The simplest place to start is in answering questions such as: What instruments have you heard are your favorite sounding? What style, both aesthetically, and playing-wise, are you aiming for? What strings do you plan on using? Do you like a warmer sound or a brighter sound? Loud and bold or soft and reserved? Open, bottled, or somewhere in between? Don’t feel limited in just looking at qin for these answers – looking at the wood combinations and response of other stringed instruments such as guitars, ukuleles, psalteries, etc. can be very helpful in determining what type of tone you prefer for certain instruments, or even instruments in general. And there is no one right answer – there are so many different sounding instruments out there, and each person has their own personal preference to what they prefer.
From these questions you can start moving into perhaps the next phase of the process, which could be choosing the woods to best reach the desired tone you are after. For example, if you are like myself, who prefers warm and mellow tones over brighter sounds, then a good place to start looking would be at warmer responding tonewoods for the top. Woods such as cedar and redwood are most associated with warmer sounding instruments, whereas woods such as the spruces led themselves more to brighter and more resonant response. Obviously there is a wide range in between, and each piece of wood is unique and different, but this is a general rule of thumb that has been widely observed and explored in the stringed instrument world. Different woods will favor different responses, which can be related back to their stiffness, density, and other physical factors. You will generally find that higher stiffness woods and woods with higher density, are more inclined towards brighter tones. This however is all relative, and should be separated into two categories for the topwood and the backboard, since the backboard woods will be much harder, heavier, and denser than the topwoods, and serve a different function in their own way.
The bottom board serves to reflect the sound inside the cavity, which is transmitted from the strings and amplified through the top board. The degree of this effect can in part be tuned by wood selection, but it is not as critical as other factors such as the design of the underside of the soundboard or overall internal structure. Nevertheless, it does play a role in tone. Super heavy, dense exotic woods such as bloodwood and bubinga will serve as a much stronger reflector and tend to be a lot brighter than softer hardwood choices, such as walnut and mahogany, which favor more lower and mid-range tones.
The combination of the top and bottom woods can in part be used to start aiming for a desired tone or effect, and can be used to strengthen certain timbral qualities to an extent. Note that I say they can be used as a start for the desired tone – a lot still is determined by overall craftsmanship and structural design, but again, this can provide a basis on where to go. For example, if you wanted a very loud, bright, and resonant qin, on the extreme end you could choose a combination such as sitka spruce and bloodwood to start.
Strongly relating to wood selection and internal design is string choice. Do you plan on primarily using metal core strings, or silk strings? This can have a large impact not only on the lengthwise top curve, nut height, and bridge height, which determines playability and buzzing mitigation, but the overall sound and style as well. Note that you can also use different woods or designs to take advantage of certain string characteristics, or design to enhance particular characteristics of a string. For example, with my own qin, many of the design choices were focused around the use for silk strings, but being able to enhance the overall volume of the strings through the instrument, while achieving a tone that was warm and balanced without sounding too open or empty. You can use choices to perhaps increase the volume of a qin for silk strings, or perhaps diminish the resonance of a qin designed for metal-nylon string. Or, you can possibly design to increase or decrease the warmth of a particular string, or perhaps make the qin more or less resonant. A perfect example of this can be seen in the unique and quite frankly really awesome creation of the first ever carbon fiber qin by Shuengit Chow. From what I have heard, this qin actually diminishes, if not eliminates the harsh metallic tones normally found with metal-nylon strings when compared with use on standard wood qins. This has incredibly exciting implications for the advancement of modern qin making methods, and truly exemplifies the points that sound can indeed be customized based on careful material selection and design. For qin, the main choice between metal-nylon strings and silk strings can almost be likened to deciding the design for either a steel stringed guitar or a classical guitar. It’s obviously not an exact analog, but is something worth considering – each style lends its strengths to different methods of play and different tonal feels. As such, choosing the woods can help impart extra flavor to the sound, or enhance certain characteristics of tone. This can be leveraged either way for both types of strings. For example, lets say you want to build a qin which will primarily use metal core strings. Metal core qin strings are inherently louder, brighter, and have longer sustain than their silk counterparts (assuming standard monofilament core and wrapping construction that is currently used for every type of m-n string out there so far, but this is a subject for another post). Using a brighter wood for the top board, such as spruce, can enhance these qualities more, if that is the tone you prefer. However, by using lower stiffness and more damped wood selections, such as western red cedar, with a back that favors stronger mid and low tones, such as walnut, you could tone back some of the brightness inherent in the metal core strings, and possibly get a bit more warmth with still good volume.
Perhaps the biggest factor that influences upon all of these considerations is the soundboard itself: how it is shaped, as well as the wood chosen. Thickness of the soundboard, which is determined primarily by the internal carving, plays possibly one of the biggest factors in tone of the qin. Too thick and it will not vibrate, sounding dull or too quite. Too thin however might sound to open, loud, or empty, though if this is how you want your qin to sound, then follow what sound you prefer. Generally however, a good balance in thickness is best. However, this also has to take into account the wood selection for the topboard. Generally, the denser the wood chosen, the thinner it can be made. Responsiveness also comes into play, which is also determined by the elasticity and stiffness of the wood. Woods with a higher modulus of elasticity will tend to be more responsive and resonant, while those with less elasticity tend to be less resonant. This factor may also tie into the overall brightness of a particular wood. Both of these factors can be coupled together to look at the strength-to-weight ratio of a particular type of wood, which also plays a role in overall responsiveness and what frequencies it may enhance or diminish.
Yueshan (bridge) and chenglu (bridge accessory) design and placement also can partly affect the tone and response of a qin. The yueshan, along with the nut, are the two primary “boundary conditions” of the contact points for the string. However, the nut is less critical since it primarily is only “seen” by the end of the string when played with open notes – for pressed notes, the boundary condition is the interface of the top of the soundboard, the string, and the finger that is pressing it down. Different left hand techniques will result in slightly different tonal quality, since this boundary condition is being changed. There are many different ways of approaching the design and implementation of the nut, but in regards to tone, I feel that has far less of an effect than that of the yueshan. However, the boundary condition that never changes is the contact point with the bridge. This condition is very important to keep in mind, and in future posts I will be discussing some of my theories on how important this boundary condition really is, as a fundamental factor to the core timbre of a qin itself. But for this post in relation to designing for tone, we will concern ourselves only with the placement of the yueshan and chenglu on the soundboard, rather than the effects due to physics of this particular boundary condition on a vibrating string. The yueshan is important because it is the major area where the sound from the string is directly transferred and coupled to into the qin. The yueshan can be attached to the qin top with three basic methods: carved to fit the qin top profile and glued to the surface, glued part-way into the soundboard in a slotted channel, or glued all the way down to the backboard, thereby separating the forehead area of the qin topboard from the rest of the topboard. Each method will result in different coupling to the soundboard, and different sound transfer channels as a result. Generally, whatever method of attachment is employed for the yueshan, the chenglu follows suit as well. As a general rule of thumb, the more contact area the bridge has with the soundboard, the better the coupling and sound transfer to the soundboard. The second and third methods of attachment listed above will result in increased surface area, and increased sound transfer. It is very difficult however to tell what exact effects each method has on the overall tone without careful and rigorous testing and measurement, but there is still nevertheless an inherent effect due to the physics of sound and the instrument itself. In addition, since the chenglu is most likely made from the same wood as the yueshan, which will almost always be some sort of very dense and heavy hardwood such as rosewood or ebony, and will be tightly fitted and glued into direct contact with the yueshan as well, it is reasonable to assume that the chenglu in part may act as an extension to the bridge in regards to overall contact area with the soundboard. For my own qin, I decided to go with the second method, fitting the chenglu and yueshan halfway down into the soundboard, mainly for aesthetic purposes, but also because I knew that I would use either the second or third method for vibrational coupling. Both the yueshan and chenglu were also fitted as tightly as possibly into the routed channel without incurring damage – they were glued in and so tight, that I had to hammer them down into place extremely hard to get them to seat properly. Fortunately, the wood I was using, gabon ebony, is extremely hard and dense, and could take the beating.
On the subject, wood choice for the bridge may also have a slight effect on shaping the tone to a small extent. A very hard and heavy wood needs to be used regardless, since it has to stand up to the wear and pressure of the strings on it, but even with the common choices between rosewoods or ebonies, there is still a range of densities. Density and elasticity both play an important role for sound transfer in materials, and this can play a very important role in determining the wood combinations for the topboard and backboard, which relates to what I talked about earlier in the post, about elasticity, density, and strength-to-weight. The simplest equation for the speed of sound through a material is c=SQRT(k/p), where c is the speed of sound through a material, k is the coefficient of stiffness, and p is the density. Stiffer materials will allow sound to propagate faster. Higher density materials have more mass per volume, which results in slower sound transmission. Again, this exemplifies design trade-offs in selection of materials, and different materials can take on various combinations, such as higher stiffness, high density, low stiffness, high density, or any other numerous combinations. Sound transfer for a string instrument is simple in concept, but very complex fundamentally. Sound is first generated in the string, which propagates through the bridge and nut or soundboard directly (depending on if the note is played open or pressed), which gets transferred partly to both the back board, as well as the air in the resonator cavity, and through the soundholes, as well as the surrounding air of the strings and instrument (though primarily through the soundholes on the bottom which directs most of the volume of the instrument.) In this regard, there are numerous boundaries which the sound transfers from, through various different solids, and between solids and air. All of these boundaries, transitions, and materials will have an effect on how the sound propagates through and radiates from the instrument, as well as its frequency response, and possible other resonances and vibrational modes, which can all affect the overall timbre of the instrument.
Soundholes, particularly on the qin, which are known as the dragon pool (larger) and phoenix pond (smaller), are where the sound from the resonator box will be released, and can play a role in determining both the volume and “openness” of a qin. Volume is the most direct: a larger hole will likely increase the overall volume or projection of an instrument. However, this can also lead to it sounding too open or empty if the hole is too big, which could be beneficial or detrimental depending on the tone you are aiming for. This becomes a careful balance, which is closely coupled to other internal factors such as total volume inside the instrument, and the design or inclusion of other features such as nayin for the qin.
To give you an example, we can look at the design choices that led to the overall internal structure of my qin, in order to achieve the tone I was looking for. I originally planned on using silk strings, but I also wanted to design the qin to have a louder volume with silk strings without being too open or empty sounding. To increase volume, I designed the qin to maximize volume and vibrating areas inside of the qin. That included carving very close to the bridge, the nut, and even in the head section between the very end and the chenglu. Depth affects resonance and volume as well, so with all of this vibrating space, I did not want an overly deep qin internally. This led to a design that is overall larger size on the internal perimeter, but having the soundboard still a bit closer to the backboard internally. This also came about in part due to the overall aesthetic design choice of having a wider and flatter qin profile. Functionally, I also made my qin extra wide so that the walls on the side nearest the thickest string and the thinnest string were not too close to the strings, which could result in uneven tone or damping of response of these two strings when pressed along the soundboard.
I also eliminated the soundposts and nayin as well. Nayin can have a noticeable impact on the tone and response of a qin – the are essentially large chunks of wood left uncarved under certain lengths of the soundboard down the center. These could help bring the notes pressed along the center of the qin be more balanced responsively with those closer to the edge, as the edge will generally restrict vibration more, unless using an extra-wide qin design to partly compensate for this, but they can also negatively affect response if they are made too thick or large. Remember though, that, for example, my qin uses unconventional woods for a qin, so the response of the woods chosen will be much different than traditional woods, and opens up potential ways for alternative methods around some of these design trade-offs when dealing with a qin. Paulownia, which is traditionally used for the top board, is not only one of the lightest woods in the world, but one of the most resonant, so the nayin may have less of a damping effect, all things being equal, than on a wood that is much more dense, heavy, and less responsive. The primary function for nayin however are to act as “sound absorbers” – in essence, to help retain some of the sound in the qin. I aimed to bypass this however with a goal of increased volume for silk while retaining a tone that was not too empty, all of which included choices such as large internal volume, shallow board spacing, maximized vibrational area, soundboard thickness, and soundboard wood selection.
Soundposts are two small posts that are located inside the qin, located between the bridge and the dragon pool, and between the dragon pool and phoenix pond, and are attached in a way that connects both the top and the bottom boards together. I left these out for several reasons. There is some debate to the overall necessity and effectiveness of these posts, but I felt they were unnecessary inclusions in my design. For one thing, they will act to deaden the soundboard pressed position directly above them, since they inherently would inhibit the vibration of the board at that point by anchoring it to the back board. For arguments regarding structural integrity, I find it hard to believe that these two tiny posts would have much of any impact on the warping of the instrument, being that the qin has such a large surface area to begin with. In summary, I see no real benefit tonally to including these, at least in my design. For some older more traditional qin I have heard stories of having them knocked out making the qin sound worse, which may certainly be the case using very traditional methods, woods, and approaches to the qin. However, as I have mentioned before, by looking at other alternative woods and design considerations, some design elements and choices can be deviated from traditional methods to potentially open up more control and customization in tone.
To compensate for the difference in responsiveness due to the non-uniformity in the wood, I also selected the more dense side of my top board to be used for the thicker strings, and the less dense side for the thinner strings. I also shaped the inside profile to be slightly thicker under the first string, and progress thinner to the seventh string. Since the redwood is heavier and denser than paulownia that traditionally used, I could afford to make the soundboard slightly thinner to compensate for this density increase as well. Its vibrational response would also be less than paulownia, which means I could potentially open up the soundholes for a louder tone without necessarily making it too open since I did not include nayin. Again, the inside of the soundboard was also made a bit closer overall to the backboard to help simulate the effect of nayin to an extent along the entire length of the qin internally when in reference to its position to the soundholes. Thus at this point, in conjunction with other parameters, I chose to have my soundholes slightly larger than average.
Sometimes, unexpected results may arise from wood selection and design. For example, on my personal qin, which uses curly old-growth redwood for the soundboard, fiddleback paradox walnut for the backboard, and gabon ebony for the bridge and nut, harmonic analysis reveals that there is an interesting additional peak that emerges in the 1khz range for particular strings, which is not normally observed for traditional qin. This peak exists across string type regardless of metal core or silk construction, so it is a fundamental tonal property of my qin. As a result, metal core strings sound a bit extra harsh with the metallic tone on my qin, though my intent was to use silk strings anyway. Note however that this is not necessarily indicative of the wood combination that I used, and can include other factors such as internal design and bridge coupling. A qin made from the same types of woods could still have a very different response than mine, though with the wood selection it will still probably favor warmer and more bassy tones. This peak however is not a bad thing, and as a whole, the qin has its own unique voice and sound profile that is measurably different from traditional qin. I did however, achieve my other design goals, in creating a qin with a warm and mellow voice, in addition to increasing volume for use with silk strings while not sounding empty or hollow. This however goes to show that wood and design choices are only at best well educated guesses, as not everything can be designed and accounted for, but the bulk tone of the instrument can still be reasonably predicted.
Designing for tone can be a complex and challenging subject when building an instrument. There are numerous trade-offs and design elements to consider, and you can’t always get everything you want. Nothing is for free, and there will be always some trade-offs depending on what you want to achieve. This all really comes down to a lot of experience and practice with working with different woods and instruments, and understanding how different choices can affect the tone. Plan ahead – make tables and charts comparing various woods and properties. Look at other types of instruments that use different wood combinations, and try to gauge how they might behave together, based on your own experience and the experience of others. Really know what you want to achieve ahead of time, and design for that, both tonally and aesthetically. Know what you prefer when listening to the instrument you are designing, whether a qin or anything else – really try to know what types of tone you prefer. Do lots of research ahead of time – wood selection, wood sources, tooling and jigs required, dimensions, plans, everything. I made master templates and tracing templates for every part, and carefully researched every aspect of the instrument I could find. Every day before I started working on the instrument, I would go over the process in my mind over and over, visualizing how I would work on the part I would be making, how it would go together, and going over all of the steps I had previously done, and planned and visualized the next several steps in the process. I spent several months alone just researching and designing the instrument, and during the whole process I always went back through all of my resources countless times, over and over, so that the process was locked clearly into my mind. Anything that had to do with the construction of the qin, I tried to access – instructions, guides, blog posts, pictures, videos, etc – even stuff like pictures and videos which were in Chinese which I could not read or understand, I still referenced, studied carefully, and took notes on. While you can’t control everything perfectly, it is still very do-able to achieve the tone you are after, with careful thought, planning, and attention to craftsmanship and design.