I'm delighted to introduce Samo Sali from Ljubljana, Slovenia.
Q1. Could you please tell us a little about your luthiery and its history?
I think it all started when I was a student and I decided to learn to play the guitar. My passion for the guitar playing was irresistible. I was lucky to have an excellent teacher who inspired me to finish a 9-year classical guitar course at a neighbouring music school. In this period of my life I also finished my diploma at the Faculty of Mechanical Engineering in Ljubljana which was about cutting processes and their influence on the acoustical properties of wooden boards. One can see more about this in my paper "The frequency response of differently machined wooden boards" – Journal of Sound and Vibration 1999, Vol. 227, No. 2. I continued with master and doctor thesis both in area of guitar acoustics. I had some knowledge in this area, therefore I decided to become a luthier which happened roughly 14 years ago with some help of Mr. Mirko Hotko, a luthier from Croatia. To me being a luthier was never a question of hand skills, but rather of understanding what a musical instrument actually is and how it performs in musicians’ hands. I use my own methods, which are based on science, to control and adjust the sound of each instrument. This does not mean that I plug my ears and ignore what I hear in my workshop and what other people tell me about my instruments. It just means that I use these methods to make my work more pragmatic. I consider science as a tool to achieve my aims; such a way of working can save a lot of time and effort, and it also contributes to the overall joy, too. To conclude, I consider myself as a highly innovative person, I implemented several innovations of a guitar so far. For instance, one of them is so called low-mass bridge which results in extremely high dynamic range of a guitar. I also like to use verified methods and techniques like double-top guitars which I prefer if I am honest.
Q2. Please describe your idea of a good sounding guitar, and what you do to achieve it? (it'd be fantastic if you could share some of your scientific discoveries as well as the designs you use)
One phase of my work before becoming a luthier was actually measuring guitars in order to define a criterion for guitar tone quality determination. I found out that there is a mathematical, physical and musical way to objectively describe the difference between good and bad guitars. I named this criterion as a "rule of consonance-dissonance" and I published it in Experimental Mechanics ("Measuring the quality of guitar tone", Vol. 40, No. 3, y. 2000). In another words, I found out that a great guitar sound has strong consonant and weak dissonant intervals in any tone spectrum in comparison to poor guitar sound. An interval consists of two frequency lines (components) which in practice represent a basic component and higher harmonic components of a tone. For instance, the second and the fourth frequency line (or frequency component) in the tone spectrum form an octave which is highly consonant interval. Next, every guitar has so called frequency response (or resonant frequencies) which tells us at which frequencies the guitar will "sing" loudly and which frequencies will not be amplified well. It is logical that frequency response (resonant frequencies) is heard in every tone we play on a guitar; it actually determines how the guitar will sound regardless of the played note. Finally, I found out that noble guitars have their resonant frequencies in ratios which are typical for consonant intervals, for instance 2:1, 3:2, 5:3, etc. From the luthier's perspective this finding means his or her goal. Thus, my aim is to design a guitar with its resonances in ratios which are typical for consonant (pleasant) intervals. These resonances should be relatively strong and their damping should be optimal. Consequently the guitar tones will be pleasant to the ear, loud and relatively long. To be evident, I developed a method which enables me to measure certain positions on a guitar top which are appropriate for increasing stiffness and/or mass. Stiffness and mass mean braces and fans in practice. I can also calculate positions which are not appropriate for gluing the braces and fans. Combining these two procedures results in "optimal" bracing of a guitar if I am allowed to simplify things here. The point is that I can use this method along with any type of a guitar, wood species, top board design (traditional or double-top), etc. Briefly, I assemble (i) neck, (ii) sides and (iii) top without braces and fans, and then I calculate their optimal position and shape. One can read more about this topic in my paper: "Modelling and Optimizing of the First Guitar Mode" - Savart Journal, 2011, Vol. 1, No. 1. Bracing pattern in my guitars is very similar to that from Mr. Simon Marty's guitars. I also discussed with him this topic several years ago and I admire his openness and willingness to help. Except of double top guitars (nomex sheet) and neck reinforcement (carbon fibre strips), my guitars are made only of wood lately.
Q3. Please tell us about your idea of improving playability, and what you do to achieve it?
Playability depends on many factors, not only on fingerboard and neck shape. Calculating of ideal neck relief took me a lot of time and I do my best to implement my findings in my guitars. In addition, I also use a two-way truss rod to improve stability of my necks and to eliminate undesired deformations when necessary. I cannot stress enough that playability strongly depends on a guitar body, more precisely on its impedance. Mechanical impedance indicates a ratio between the force and resulting velocity. In another words, more intensive vibrations of the guitar top mean smaller impedance for a certain frequency and string excitation force in mind. When energy drain from strings to the guitar body is optimal then player feels it as a good playability. Mostly we pluck the strings with one hand but other hand is of course connected with it, that's why a nice feeling in one hand usually means the same feeling in another. So, if guitar top is not too massive or too weak, then energy from strings will be transformed to it in an optimal way. Of course this should be true for all (or most of them) main resonant frequencies of a guitar which strongly complicates luthier's reality. In another words, a good luthier must control impedance of all major resonant frequencies of a guitar and these frequencies mainly depend on a top board design. If I am allowed to simplify then a massive (heavy) top usually means a good sustain and narrow dynamic range of an instrument. Logically, a light top results in a short sustain of guitar tones, especially if we talk about guitar's first string. I found a way to control some of the most important resonant frequencies in the frequency response of a guitar. This means that I can affect the impedance of these so called modes of a guitar. Each resonant frequency or mode has its modal shape, amplitude and damping. Once you know where on the guitar top a particular frequency exhibits its maximal amplitudes, you can control it by braces and fans. One can read more about this in my paper "Positioning of braces on a guitar soundboard" - Proceedings of IMAC-XX: a Conference on Structural Dynamics, Los Angeles, California, February 4-7, 2002. Sometimes I also glue a lead weight (several grams) onto a specific place on a top which then drastically affects particular guitar mode. A good example of this is any high tone on a first string, usually above the 12th fret: before the lead weight on the top the tone can have very short sustain but after mounting the weight from the inner side of the top the tone becomes perfect. The secret is where to glue the weight.
Q4. Please tell us your opinion about the traditional finishing method (French polish) and new methods (lacquer, catalysed finishing, etc).
For the last 6 years I use only shellac on my guitars but I use spray gun mostly. If one wants traditional French polish where a cotton rag and a lot of hand work instead of spray gun is used then this is also possible. If I am completely honest, every top on my guitars is first French polished and then sprayed if not ordered differently by a customer. In hardwoods I do not close pores with any type of pore filler. My opinion is that closing pores does not contribute to the fine sound. Namely, pore filler only increases the weight (specific density) of the wood and it does not increase its stiffness. The fact is that sound energy radiated from the guitar is proportional to the stiffness of wood and inversely proportional to its density, so I hope I have explained everything. I strongly agree with everybody who claims that catalysed finish (i.e., polyurethane) is not an optimal protection for a fine classical guitar. It simply adds too much weight and guitar sounds much worse than it would sound without any finish or with let's say French polish. I think lacquer (i.e., nitrocellulose) is somewhere in between but definitely closer to the French polish than polyurethane varnish for instance. I used all types of finishing which I have mentioned here and I must say that spraying shellac or applying shellac by French polishing technique are superior methods in terms of sound. Unfortunately, protection properties of shellac are poor, however this must be traded for the sound quality and I believe there is no doubt about it.
Q6. Do you have a preference for any particular string type or tension when you design/make your guitars?
Not at all. A lot of different types of strings (nylon, carbon fibres) along with different tension levels work well in Sali guitars. It is interesting that carbon fibre strings sound nice on my double-top guitars, they do not exhibit any harsh effects which are not rare on many guitars with such strings.
Q7. How does the increasing rarity of some woods, rosewood for example, impact on your methods, and the quality of the end product?
Indeed I was surprised not long ago when my wood supplier from Germany told me that he is not dealing with rosewood any more. If I remember correctly then this was more a consequence of state regulations than rarity of rosewood, but for me the effect is the same. The fact is that I have found another supplier without any troubles, so I hope this issue is not critical yet. My supplies are huge, so at this moment I do not have any problems. For instance, I bought wood for several hundreds of guitar necks thus I hope I have enough to the end of my life. I am sure we will find out another solution if some wood species will vanish out of the market. So to answer your question directly; so far I do not have any problem because of rarity of some wood species. However, I would not be surprised if it happens soon.
Q8. How do you see the future of this beautiful tradition in the 21st century?
I think all will be fine. Enormously large quantities of electric guitars and related music cannot be seen as a competition to classical guitar. Next, music is an important part of our lives so it is logical that this will continue in the future. What interests me more is a question if we will see any important modification of this instrument in the near future. Namely, we all know that double-top guitars and lattice-bracing guitars are not the same as traditional Spanish guitars, so one can say that two important modifications have already appeared on the scene since Torres's introduction of so called modern classical guitar. In my area I have noticed some new names in this business so I assume that popularity of luthiery is not endangered. On the other side I have also heard for big troubles of some luthiers in Europe to sell their products. It is clear that competition is big; the quality level of guitars is increasing rapidly, thus only the best and those with a lot of luck can survive in a long term.
Ljubljana, 6.2. 2016
Dr Samo Sali also gives conferences about guitar and guitar acoustics.
Would you like to know more about guitar acoustics? Dr Sali is happy to answer your questions. Please don't hesitate to ask Dr Sali using the comment system below or contacting him directly.