Interesting links on wolfs
27.06.2016
Wolf tone at C (B1+) is solved at making stage, as described 29.02.2016. The problem is that every maker must test the limit for him self (assuming that the plates are made in the same range). There is very little differences in B1+ dB level on the three Soil copies. The latest one is just under a threshold and does not wolf, only a strong note that is acceptable.
29.02.2016
This should minimize the wolf (on violins optimized as described here: Modal goal - Strad average)
Bass bars can be optimized for low weight ~3-3,5 g, instead making it ~4-4,5 g with a peak at where B1+ is strongest and leaving the area drawn a couple of tenths thicker.
30.01.2016
After a Siberian cold wave, the Soil #2 has now cycled once with very low humidity (5-10% at lowest) and then up again a week to 35%, it was time to give it final trimming and continue wolf elimination research. As I'm not going to change the parameters and bass bar optimization for my next Soil. I had to find a solution that works on a finished violin.
This is the solution which lies in first finding the right after length for a light box wood tail piece. The gut was shortened so that this frequency was near B1+. After that it was possible to split B1+ with a rubber between D and A string. To do this you need real time FFT software. It also effects the sound to be a little more bright when B1+ is split to be high on the right side. The middle images with a split in the middle of B1+ is the best solution. This is also confirmed by Martin Schleske on his web site.
This is also the reason why not to trust B1 mode readings from other makers. The setup quite often skew the frequencies and gives false readings. For example the true B1- reading seen here is messed up with a heavy chin rest. The true B1- is actually in the low valley.
19.12.2015:
One of the elements in "reproducing" this wolf tone is bass bar optimization. On the four violins having this wolf, the bass bar is optimized to be light and right on the edge.
I strongly believe that upgrading to a modern bass bar on Cremonese was to eliminate this wolf on B1+, as the old bass bar with modern setup would make C unplayable (many Strads and dGs are tuned to have B1+ ~525-530 Hz in playable state) Add to that, that it is possible to re-tune the top to it's original state with bigger bass bar with skillful tuning, I think it could be a likely scenario.
Optimizing the bass bar:
Album of photos Wolf B1+ research
B1+ has a peak at bass bar culmination (Stoppani/Kreit images on B1+)
Top can have the same frequency if keeping weight/stiffness ratio the same (with and without strips center join fix images)
Bass bar optimization (image above)
Tracking the B1+ culmination with blue tack eliminates the wolf (523 Hz) on A, D, G string, B1- & B1+ frequencies are not altered, only B1+ dB level, confirmed with real time FFT while playing, with and without the blue tack weight
06.12.2015:
The wolf tone on Soil #2 revealed itself after a week. It will almost go away after some months though, it behaves exactly like Soil #1. I now have four violins on a row with this attribute (at 40% humidity). Light back (98-100 g) and light bass bar will give a strong B1+ (it does not matter if it's thick or thin in the middle), if tuned to ~525-530 Hz with chin rest this Will happen!
I have experimented until exhaustion with finger board, string after length/weights/tuning.
The only valid eliminators I have found is following
Strings; Zyex and Dominant are wolf prone, changing to something else reduces the wolf to minimum.
Changes the tone to a somewhat different violin
Search for the spot on the top where minimum weight completely removes the wolf
Does not change the tone, very little weight is needed!
Older update:
Many great Strads and Del Gesus have wolf notes. Quite often this phenomenon is blamed on that it's an "Old" instrument. This is not why wolfs occurs. In great violins that are tuned to the limit this will happen from time to time, because the body modes B1-/B1+ are strong in dB level and near notes A (440 Hz) and C (523 Hz).
There are several ways to knock down the dB level of B1+. Tuning tailpiece, fingerboard, lighter/heavier strings. Playing around with the sound post is not the solution. The best way is to use technology, like real time FFT analyzer, to track and take down the dB level of B1 modes. A wolf note can also show up as a harmonic in Fourier series which complicates things further.
Following shows a wolf note occur at C natural when hitting it a little sharp. This tube demonstrates how real time FFT spectra occasionally shows the B1+ as a double peak on the right side at 534 Hz. In summertime when humidity is going up B1+ will go down to about 525 Hz, the dB level will be weaker and the wolf most likely won't show up. Until that it has to be dealt with. On this particular violin, the modes have been tuned to B1- at 443 Hz and B1+ at 537 Hz (at ~6% moisture content)
In following tube Ida Haendel have this problem on C# (higher B1+) on her Stradivari 1796 (4:00 ->)
Stradivari wolf, note on C (6:40 ->