As mentioned, the dual chain coupler on the Potvin drive did not have a harmonic dampener. Also, mentioned, a dampener is a good thing. However, the lack of a formal dampener may not be as bad as it sounds. The chain coupling and the blower drive with its impellers, all serve to dampen some frequencies. I'm not sure of the resonant frequencies involved but it is probably better than no dampener at all.
On current blower drives using a timing belt, the belt does as good a job as a dampener and it is not needed.