Double Bass Tone?, Volume?, Resonance?, Can't explain, please read.

[Bob Branstetter]

Actually, one of the contributors went on to apply the techniques from the book and emailed me some photos and info:.... I can send you some copies of the pages of the book that shows the recorded chart of cello de-damping. It gives you a kind of guide line for weight, speed and time schedules. Each cello is different and if it shakes violently it some speeds you have to speed up to the next pitch/speed that it runs smooth. The cello is already resonant at the violent point.

You need not send me any pages from the book since I own the book and have been using the method on basses since shortly after Mr. Strobel first published the book (as you will see if you go back and read the early posts on this thread). I see that you are not using a real stroboscope as recommend by the author. While a tachometer may work for setting the speed, I question the accuracy, and the fact (because of the small surface area of the laser) that you can't watch the top and bridge movement in slow motion as you can with a stoboscope. IMO, this is important since you are able to use it as a guide to prevent potentially damage from over weighting of the excentric imbalance. What is the range and precision of the laser tach? You mention that the cello shakes violently at some speeds. I don't believe it is the speed alone that is doing it, it is the amount of weight you are using on excentric. It appears from one of the photos that the center of mass of the imbalance may be more than one centimeter from the center of the shaft. If that is true, the actual imbalance would be more than the 4.5gm-cm recommended by Prof. Reumont and Lothar Tews. The speed does vary in the process and must be constantly watched and adjusted to hold it constant until it will no longer change over time. BTW - How do you regulate the the balance on the screw if you use locktite make it hold? The only screws I've ever had loosen are the ones that hold the device to the bridge itself. When they loosen, it makes such a increase in vibration noise that you hear it long before it can do any damage.

 

[jlattuada]

I was merely passing on information I received in an email. I am not the person who has executed the dedamping. Just an interested bystander. Your questions are good ones, but alas I can not answer them. Though I have enjoyed this discussion and learned a lot from your contributions to the thread. Thanks