AH! now I undestand,
I just read http://www.cello.org/index.cfm?fuseacti ... &tip=tip50
I have experienced wolf tones then, just not anything that made me want to smash the guitar up yet. Slightly duller tones or louder ones, yes I am familiar with those and notes that never seem to tune as I'd like particularly in the relationship between octaves across the 4th and second strings. I was thinking a wolf tone was a complete disaster rather than a minor flaw especially after hearing the likes of Segovia rattle on about them. I imagine the problem was worse in days gone by with poor string quality, anyway I've learnt something new today - again!
FWIW unless there is a major problem with an instrument it doesn't pay to get hung up on factors like the cedar or spruce debate or even what type of spruce and the odd note that doesn't resonate quite as desired. THE most important factor in owning and keeping a guitar is its playability, a musician will never make the best music on an instrument they hate playing, playability is the starting point, the sound next, everything else comes after that with cosmetics last.
Thanks for that link - it's quite a good article, more comprehensive than most. Believe it or not, I think it still only touches on the subject! Bear in mind though, that wolf notes tend to be more of a problem on bowed instruments than plucked ones. On a violin (for example), the energy input to the string is continuous (as long as the note is being played), so that if the note lands on (or near) a resonance, you can get the "wildly fluctuating and uncontrollable tone" described in the article. On a guitar, however, once the string has been plucked, no more energy is put into the string. The most common effect of a wolf tone on a guitar is that you get a loud, fairly unpleasant tone, with little sustain. This is because the energy is lost very quickly driving the resonance. The precise quality of sound you get varies depending on how close the resonance is to the note played (and on lots of other things I think!). All guitars have resonant frequencies, the most significant being from the air volume, the top, and the back. Each of these resonate at a number of frequencies, so the system as a whole is highly complex.
My approach thus far has been to use experience, feel and ear to minimise the effect - but I'm now starting to bring a little scientific method to bear to analyse the various resonant frequencies, and relate these to the tone of the completed instrument. Whether I will use the data to change the way I build at all, I'm not sure yet.