Wolf tone research and trivia
Here is a link to one of the best articles I’ve seen explaining Frequency Resonances, which cause wolf notes on a cello.
Check out the world’s most expensive wolf suppressor! A four million dollar sphere hanging like a pendulum in a skyscraper in Taipei.
Below are two of the many physics experiments used when developing Saddle Rider’s Wolf Rehabilitators set:
Imagine stringing a rubber band between two nails and tuning it to “A=220 Hz.” Pluck it for a lovely twang which dissipates pretty quickly. Now, imagine pinching a one-gram fishing sinker onto the middle of the rubber band and plucking. What happens? Most peoples’ intuition tells them the weight will deaden the sound of the rubber band and shorten the duration of time it resonates when plucked. But that intuition is wrong! The pitch drops and but the rubber band resonates significantly longer and with greater amplitude. Now, imagine taking a pair of pliers and pinching a half-inch long piece of wire to the rubber band, and pinching the same fishing sinker to the end of the wire, so it’s suspended a half inch below the rubber band. What happens when you pluck the rubber band now? It stops resonating almost instantly! The reason? Because the fishing sinker forms a pendulum that swings opposite to the rubber band action, dampening the rubber band just like two sound waves, 180 degrees out-of-phase, cancel each other out.
By carefully designing the asymmetry of a button clamp wolf rehabilitator, it is possible to achieve the an effective balance between muting extreme frequency resonances or “wolf tones” (when the pendulum action kicks in), and enhancing the less extreme resonances (when the whole clamp, wire, resonating string assembly work together as one system), as in the case of normal, non-wolf, notes. To find the correct balance points for the wolf rehabilitator set, I started with symmetrical, oversized, button clamps and lathed them down in dozens of iterations until I found the optimum balance points for each top and bottom. The 4.7 to 7.3 gram incremented range of the Saddle Rider Wolf Rehabilitator set is what seems to be the sweet spot for most cellos, except for the occasional instrument that responds better to the included magnet-style resonator.
Magnetic Resonator Research:
Not long ago, a client sent me a Krentz Resonator that he was abandoning in favor of button-style wolf suppressors. During shipping, the plastic piston tube became disconnected from the main body of the magnet, offering a great opportunity to perform some experiments! Right off the bat, I noticed that the 3/4 inch primary Neodymium magnet and the 1/4 inch button (also a Neodymium magnet), sounded pretty decent on my cello – better, I thought, than a complete Krentz resonator that I had tried at an earlier time. To confirm my intuition about this, I re-attached the plastic tube/piston assembly, and compared. It did, indeed, mute the cello a little more than the magnets, without the tube, and didn’t seem to control wolf tones any better. This led to another question: How does the piston assembly sound, when suspended between two magnetic fields in reverse polarity — as the Krentz is constructed — compared to flipping the piston 180 degrees so it sticks to the tip magnet in a fixed position, and no longer is free to act like a piston? When I compared the two positions, I couldn’t hear a discernable difference. (i.e. the piston does operate as a mass, helping control wolf notes on some cellos and muting others, but the advertised “piston action” is undiscernible to my professional cellist’s ears).
Moving on to the next subject of inquiry, I investigated the felt pads on the magnet where, from a physics standpoint, most of the “piston” or “out-of-phase frequency modulation” (if I may coin a phrase) actually occurs. The felt pads, testing confirmed, really do make a significant difference to both the sound and the wolf controlling properties of the magnets. The Krentz design has centered in on some pretty well-functioning felt pads, as well as an overall mass in the ballpark of what my experiments showed worked best. It weighs 35 grams in total, which is a bit heavy, but still okay. I found a 25 gram total mass sounded better (i.e. a 3/4 inch base magnet and 1/4 inch top magnet, identical to the Krentz weight without the piston assembly), and controlled wolf tones just as well. Further, I found that a 35 gram magnet assembly (1 inch base magnet with the same 1/4 inch top magnet) sounded and performed virtually identically to the Krentz (also 35 grams), provided that the characteristics of the felt pads were the same. Using lighter magnets, surprisingly, didn’t necessarily lessen the tone filtration, and, less surprisingly, didn’t control wolf tones as well. Small changes to the thickness, hardness , and material of the pads solicited significant changes to the magnets’ performance, so experiments with those variables formed the bulk of my research into magnet resonators.
Summary:
I found that magnetic resonators can definitely control wolves, as can button-style fixed-contact point wolf rehabilitators. The magnets are a more extreme approach, and less targeted to specific frequencies. Both methods require adjustment and experimentation to optimize an instrument’s tone and response. Some cellists like the way the magnets “firm up” or “focus” the bass register of an instrument. I found that using button-style clamps on a cello C-string can have a similar effect with less frequency filtration. In the end, it’s a very personal choice, and one that tends to change with the weather.
