I don't know if someone else has said this already, but I for one am not hearing any sudden increase in volume when doing that. Quite the opposite, in fact. I'm hearing a gradual decrease in volume, followed by a gradual return. This happens two times. First, between 5700hz and 6500hz, and the second time, between 7900hz and 9000hz. What's going on here?
If it's any indication, I'm using a pair of Sennheiser HD202's.
Doesn't this just mean that your headphones have a massive dip at those frequencies extreme enough to not even resonate? Just a thought, I'm no expert. The tuning process worked very well for me.