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Cello Wolf Note


David A.T.
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Hello MN,

I have a wolf note around 158Hz (~D#2) on the first cello I built.

I decided to try to rework it.

I know that  the  bass bar is weak compared to standard. So I was thinking to make a new one as it could reduce the vibration of the front. But I had doubt that it would reduce in the right frequency range.

Then before dissambling the front I made some Tap tone test.

 

The cello is dissassembled from all fittings without string , sound post... I also removed the fingerboard. 

I proceeded with some repeatability test of the tap tone and decided to make a 1/12 octave filter to make the charts easier to compare. This is why the charts seems to have less value in the high frequency range as usual charts from Audacity.

then I tap tone on The Front, the Back and the Neck.

I found that there is a mode on the neck chart closed to the wolf note (green curve at 150Hz) compared to Front/back (Red/Blue).

 image.thumb.png.84a2ef4d06632eb07aa3b77c528c8819.png

 

 

I also noticed more vibrations in the neck when I was playing it

Could it be the reason of the Wolf note? if yes any idea what could be done ?

 

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Thanks. I was thinking to look for the root cause  and solve it without  eliminator. It could be my last option.

ON cremona tools there are some tips in the description. https://www.cremonatools.com/wolf-resonator.html. It says that when placed close to the bass bar it has more effect.

- then can a stronger bass bar also help to remove it (by making higher bar in the bouts) ?

- could the resonance of the neck be this original issue of the Wolf?

if there is a chance that a stronger  bass bar lower this mode I will do it. Before dissembling the front I will  redo some Tap tones with glued fingerboard and soundpost to see how it shift - also listen any suggestion from MN.

 

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Prof. Hesse, who invented the “Lupus ex”, which later became the “resonator”, spent years at Dortmund University researching wolf notes. He told me that a wolf tone comes when the top to bottom vibration of the belly comes into a turbulence with the side to side ones. Glueing in something with the same resonance takes this turbulence away. The wolf eliminator is sure as hell streets better than demolishing your cello. I always tell my customers that any cello that doesn’t have a wolf is junk.

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There are many methods to ‘kill’ the wolf but unfortunately they kill often more than only the wolf, in extreme cases the whole cello sounds completely muted. 
 

As Jacob pointed out, all good cellos DO have a wolf somewhere. Good cellists know how to play around the wolf. Or as one cellist once told me ‘If you want to play the wolf you can do it. But the wolf is one of how many notes you can play on a cello?’ 
 

only if the wolf makes the cello absolutely unplayable you should seriously think about something. To avoid it from the beginning you shouldn’t thin down the top below the bass side f-hole too much. 

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a Krentz might help, yes. It is the best choice for a wolf killer I know.

There are a lot of small things that each can influence the severity of the wolf. In combination that can do a lot. Check for open seams, loose blocks, etc etc. Well fitting sound post and bridge help, also the position of the sound post can do things. The sound post should not be too loosely set! The type of tail piece (weight, material, length etc etc) and even tail cord, and also the position of the tail piece in relation to the bridge can have very big effects on the severity of the wolf (and sound in general). End pin fit can have an effect (should fit well), and end pin material and/or weight can also make a difference. Some strings will exacerbate a wolf dramatically on some cellos. I have a cello that has a terrible wolf with any other g and c string apart from Larsen Magnacore Arioso. So, there are a lot of things that can do have an effect. It is really trial and error.

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11 hours ago, jacobsaunders said:

Prof. Hesse, who invented the “Lupus ex”, which later became the “resonator”, spent years at Dortmund University researching wolf notes. He told me that a wolf tone comes when the top to bottom vibration of the belly comes into a turbulence with the side to side ones. Glueing in something with the same resonance takes this turbulence away. The wolf eliminator is sure as hell streets better than demolishing your cello. I always tell my customers that any cello that doesn’t have a wolf is junk.

I'm not a professor or a maker, but did start my engineering career doing resonant cavity filters on satellites. My opinion can therefore be taken with a pound of salt, or dismissed altogether, but this explanation to me has never jibed with the fact that wolf notes (at least on cellos) can often be killed by dampening the afterlength of the strings. Maybe I should say the explanation seems incomplete as to how that body resonance interacts with the tailgut, tailpiece, and afterlength of strings. Body resonance alone does not seem to me to be a sufficient answer.

To the OP, to me it seems like a neck resonance is going to be dampened by gripping the neck, if nothing else. 

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52 minutes ago, glebert said:

I'm not a professor or a maker, but did start my engineering career doing resonant cavity filters on satellites. My opinion can therefore be taken with a pound of salt, or dismissed altogether, but this explanation to me has never jibed with the fact that wolf notes (at least on cellos) can often be killed by dampening the afterlength of the strings. Maybe I should say the explanation seems incomplete as to how that body resonance interacts with the tailgut, tailpiece, and afterlength of strings. Body resonance alone does not seem to me to be a sufficient answer.

To the OP, to me it seems like a neck resonance is going to be dampened by gripping the neck, if nothing else. 

Possibly, since all celli that are any good have a wolf if you look for it, one could wonder if there weren’t two distinct ways of going about this question. One being to manipulate the cello until it doesn’t work properly any more, the other to remove this turbulence

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Cool advices. Thx for all tips.

The cello is for me well balance. Just this range 150hz has an issue (and when I start to think about it I can't keep thinking about what I can do) . 

So I will glue back the fingerboard, try several tailpieces and maybe buy a resonator. 

True that if I make a New bass bar this could also affect the tone in many range and then I would have a bigger problem.

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Yes... every cello has a wolf and when you attach to, or modify the body, it will change the location of the wolf... but sometimes a change will make matters worse, so that is why the Rezx magnetic modulator was developed... you can move it ad nauseum to find the perfect spot without cost and without affecting the integrity of the instrument. If you find a spot that suits your need then that can be duplicated in a permanent alteration, but alas, often that spot changes with time, humidity and temperature... so a permanent alteration of the instrument may not be a good idea.... and so, back to a moveable resonance modulator that can be moved on a whim.

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16 hours ago, glebert said:

I'm not a professor or a maker, but did start my engineering career doing resonant cavity filters on satellites. My opinion can therefore be taken with a pound of salt, or dismissed altogether, but this explanation to me has never jibed with the fact that wolf notes (at least on cellos) can often be killed by dampening the afterlength of the strings. Maybe I should say the explanation seems incomplete as to how that body resonance interacts with the tailgut, tailpiece, and afterlength of strings. Body resonance alone does not seem to me to be a sufficient answer.

To the OP, to me it seems like a neck resonance is going to be dampened by gripping the neck, if nothing else. 

I did a little bit of FEA analysis a while back while looking at adjustable weight wolf eliminators - I think the mechanism is just a tuned mass damper.  When used properly, it's tuned to take energy away at one of the overtones of the typical wolf - you can get at this primary tuning freq by bowing the string afterlength with the wolf eliminator and if you tune that to the same note as the wolf, it takes away just enough to reduce/eliminate the wolf.  Lighter is has a narrower tuning (more effective at the target freq - think narrow resonance peak), heavier has a broader spectrum (less effective, easier to tune).  I had a Luis and Clark with a terrible wolf and this method worked amazingly well if you got the tuning just right, on the L&C and every other cello I had, but it was finicky and I had to readjust every once in a while.

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1 hour ago, David A.T. said:

Really? So far I am the only one to notice the wolfnote on the cello. Then maybe I don t play it too bad  :P.

Everyone notices it, but some players say it's not a problem, they'll take care of keeping the wolf at bay. Their words, not mine.

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Many reasons : wanted to change the tailpiece (ebony gewa i don t like it), wanted to reduce the fingerboard width by 1-2mm (my first cello, I had many uncommon and not convenient  dimensions). Maybe soundpost change (1.5years old). 3 pegs to redo because they were becomming too shorts, holes were too large...and then it was opportunitty to try to kill the wolfnote. It is also opportunitty to better understand how all parts react together. This vidéo shows how i built it.:

At 2:58 you can see the bass bar. I know now that I made it too weak. But the cello has à nice tone that I like . Just this wolf note is the issue.

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9 minutes ago, David A.T. said:

Many reasons : wanted to change the tailpiece (ebony gewa i don t like it), wanted to reduce the fingerboard width by 1-2mm (my first cello, dimension were not fine ). Maybe soundpost change. 3 pegs to do because they were becomming too shorts...and then it was opportunitty to kill the wolfnote.

Semi-demolishing a cello with a view to eradicating a wolf note seems reckless. What are you going to do when you've built it back together again, and it still has the wolf (or a different one) apart from biting yourself in the behind

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23 minutes ago, jacobsaunders said:

Semi-demolishing a cello with a view to eradicating a wolf note seems reckless. What are you going to do when you've built it back together again, and it still has the wolf (or a different one) apart from biting yourself in the 

Understood,

 it is my sandbox.Decision is easier to take than on a cello made by someone else. Considering above answers I will not go further.

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