My bass has a terrible wolf tone around the octave A on the A string when played arco, which also happens to a lesser extent on the same note on the D string. It's an un-named flat back carved German bass with Spiro Mittles. I've been playing a little more around the octave lately, so I tried a wolf eliminator to sort it out, the Lup-X brass variety. The afterlengths on my bass are an octave and a fifth above the open strings, and I found I got the best results with it on the A string afterlength and placed so that the string between the wolf eliminator and the tailpiece was also pitched around A. This has flattened out the wolf tone almost completely, with a small but not unpleasant change to the tone across the rest of the bass. So, this would seem to be a success, but I'd like to understand a little about what the weight is actually doing. Is the vibration of the weight absorbing some excess energy at this frequency, or is it more complex than that?