Carving the plates
Carving the plates for the X and O fiddles was fairly straight forward. The basic design of the plates is “strong in the middle with thinner areas in the upper and lower bouts”.
I set up a rig to observe the Chladni patterns. These are produced by supporting the plates on foam pads over a loudspeaker and subjecting them to a range of frequencies produced by a tone-generator app. When the tone generator hits a resonant frequency for the plate, it will start to vibrate in a particular pattern. This pattern is revealed by the glitter that has been sprinkled on the plate surface. Some makers monitor these patterns as part of their violinmaking process. I haven’t used them since I was in school, and I found it quite tricky to produce some of the higher frequency modes. You can easily find the the major resonant frequencies by simply tapping the plates and listening to the pitch of the tone produced, and this information is probably more valuable than the actual shape of the vibrating areas. However, this particular project is about the mode shapes and how different carving patterns might interact with them.
I had carved and thicknessed both sets of plates so that they had the same X mode frequencies, (164 Hz or E3). The question was how much would the different carving patterns change the frequencies of the O modes and would the relationships between the X and O modes change the sound of the fiddles?
The O modes from the insides of the X and O-fiddles, superimposed onto their outsides. The O-fiddle formed a much less distinct pattern and at a slightly higher frequency (389 Hz, vs 381Hz) than the X- fiddle. Apparently, the O carving pattern, with its extra wood about where the mode would normally form, impaired its ability to vibrate freely.
Based on things like the clarity and sustain of the tap tones, the way that the wood felt when I cut it, and the way that the plate flexed in my hands, I had the intuitive sense that the X-fiddle would be the brighter, clearer and more responsive of the two fiddles. Ultimately, most of this proved to be wrong.
I kind of made up the scroll carving patterns as I went along. I stumbled into an idea for the X-fiddle scroll that I liked: scales on the back which turn into armadillo like plates on the sides. If I’d planned this out better the execution of the the idea would be better….. and the scales wouldn’t be upside down. I like the O-fiddle scroll a lot more, a simple design that looks quite natural.
When I was designing on paper, I much preferred the look of the X-fiddle. I thought that the O-fiddle was rather plain. But as soon as I started carving, it seemed to come into its own. With the texture of the gouge marks there was plenty of visual interest there. It had a more natural, organic look, whereas after a while the X-fiddle started to appear to me to be fussy and gratuitously decorated. This feeling only got stronger in the varnish and finishing process when I added contrasting red panels.
I invited a friend, Ivy Zenobi, to play the violins. As with the Turtle fiddle, I felt that the sound of these two violins was not radically different from that of my normal violins built on the same Del Gesu model. In addition, I felt the variations in tone fall within the range of variations that I would expect between different instruments that I have build the same model. In short: I don’t think that the different carving patterns had any significant effect on the tone.
Violin tone in general is much less susceptible to variations in graduations (thicknesses) than is widely believed in the trade.
Many of the decisions in making a violin involve the stiffness-to-weight ratio of different materials and different structures. Generally we choose woods, like spruce for the top, that have a high stiffness-to-weight ratio, so that the violin will be strong enough to withstand the forces from the strings, while being light enough to be vibrated easily. I’ve been wondering if some of the scalloped or fluted patterns that I have been making recently might have an effect on the stiffness-to-weight ratios of spruce and maple. And if so, might it be possible to come up with designs which remove unnecessary mass while retaining strength – rather like drilling weight reducing holes in race car steering wheels or aircraft wing ribs? I have some wood set aside to do some tests on.
See more pictures and dimensions of the finished violins in my Portfolio Gallery.
You ran that middle ridge right threw the f holes on the O and the upper bout of the X, purposely ?
Keep on looking out & looking in !
Yes, I like to keep the areas above and below the f-holes thick. At the top of the F it helps stop the arch collapsing and at the bottom of the F it helps to bring more of the plate into play