The Hub

I did a pretty big update to my web tools last week. These are updated from the older versions I had up on celestialinstruments.com. There’s an updated FFT tool now, plus mode detection for guitars and plates, wolf note detection, played-note energy transfer, monopole mobility, plate thickness calculation, and 1/2/3/4 DOF modeling that can be prefilled from FFT data. The part I’m most excited about is being able to fit a measured guitar re…

In Michael Baskin's on-line video, he uses a frequency test of a guitar in the white to determine whether to thin the lower bout before finishing. The guitar in the video has a bridge attached. I'm wondering if this is the final bridge or something temporary. If the latter, how do the results compare to the final frequency analysis? I've used a bolt-on bridge to do the same, but don't have enough data points to draw a firm conclusion…

For my current mandolin build, I set out to answer 2 questions: 1. Whether to use physical deflection or frequency analysis to measure stiffness, and 2. How well can I measure wood quality in rough sawn form? (T. Gore says it needs to be planed smooth and rectangular for frequency analysis.) I have 4 different topwood species available for my current build: California Sitka, Englemann, Lutz, and Coastal Redwood. The billets range from 37…

Hey folks, I put together a video showing how I measure the long, cross, and transverse frequencies on guitar top plates before thicknessing, following the Gore method. I also walk through using the calculator I built (based on Trevor Gore’s equations) to get target thickness and track density / young's modulus. Fair warning: the video’s a bit YouTube-y in tone thumbnail faces, a little energy for the algorithm, but the content is genuine…

I've been testing all my top and bracewood to find the best combination of stiffness and density, optimize plate thickness, etc. I started with Nicoletti's spreadsheet which calculates both stiffness and density, but since I was also testing deflection, I decided to compare the flexural modulus using that method (with the formula from T. Gore's book) on the same plates and bracewood. Unfortunately, I'm having trouble getting a satisfa…

Initial frequency analysis of this D28 copy (done with a temporary 35g bolt-on bridge and the back plate taped on) is VERY LOW. Main air resonance 83.5hz and top monopole 156.6. It's standard Martin scalloped X-bracing with a torrefied Adirondack top. Since I can still easily access the bracing, I'm thinking of going in and laminating wood on top of the X brace to stiffen it. Other options would be a very light bridge, though I'm not…

Hi, I just glued the bridge on the dreadnought I'm building and generated some Chladni patterns. I have the monopole at 188 Hz, long dipole at 335 Hz and cross dipole at 378 Hz. I would expect the cross dipole to come at a lower frequency than the long dipole, but they seem to be reversed. Does anyone know why this happens? Pictures attached. Any comments about things you can see on them, good or bad, are welcome :) Thanks! Jorge

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