Down at the C!

Hey, today I tuned the last 3 bars of the lowest octave, D, C# and C. And again, these bars needed a slightly different approach, this time making full use of all that Bork's paper had to say about tuning: How to get the f10 down without lowering any of the others.

Here are some pics of the D:

That is the D bar after full triple tuning. Note the deep groves at each end of the bar: This is the groove that lowers the f10 without interfering with f0 and f4. In addition, the final few Hz down for f0 were done with a scraper, see the very thin groove in the center. The rest of the bar followed the approach 6mm across the arc, then down between the areas for f4, and then f10/f1. Behind is the diagram that proved to be of great value while tuning the bars. Thanks, Mr Bork :).

Here are the spectra of the D-bar during tuning, with the final measurements of D:

Next: 2 bars have to be redone, the F# and G of the 2nd octave. No fix could bring freaky F# back to normal again....

Stay triple tuned! Soon, the marimba will be finished!

Triple tuning video

As promised in the last post, I've made a small video explaining how to triple tune a marimba bar. The bar, the lower D#, behaved very well, and could be triple tuned in approx 45 minutes, including the video setup time.

3 Bars to go ;) ;) ;) Stay tuned!

Down to 4 bars left!

Just a quick, text only note: There are only 4 bars left to tune, the 4 lowest ones! Tuning the last octave, I've found a really quick way to double/triple tune a bar, within 30 minutes maximum! I'm thinking about making a movie of one of the last four bars...so you can believe me.

Here are the steps:

• Remove 6mm material between calculated beginning and end of arc.
• Remove another 3-4mm in the center right away.
• Measure: The bar should have 3 nice spikes. f0 and f10 already quite close, f4 way to high.
• Tune down f4 by removing material in 0.5mm steps from the position of f4 towards the center. Keep an eye on f0 and especially on f10. This creates a step of approx 3mm down from the first 6mm. If f10 gets close, stop extending the f4 area towards the center, keep it closer to its core area.
• When f4 is almost right (say 1-3 cent up), tune down f10 and f0 in the center. Measure often, watch f10 closely, and f0.
• When f10 is right, and f0 is still too high, scrape at approx 2cm left and right to the center. This brings down f0 only, and does almost nothing to f4 and f10.
• Here you are: You've just triple tuned a bar in no time at all, typically 30 minutes.

You'll see that in the upcoming video. The locations are all taken from Bork's paper and the graph of the regions of influence for the f0, f4, f10 and f20. The graph really is like a map, which provides orientation on the unknown bar.

Next up: Video, sound samples! Stay tuned!