Éee gads! I am going deaf! I have been charting the frequency response of my setup. This includes the DAC/amp, the headphones, and my ears. I find the frequency range to be much less than I expected, 35 Hz to 12,000 Hz! There Is a substantial rolloff at 12,000 Hz. This must be due to my ears. My ears appear to be that of a man who is ten years older than me! Also, at some frequencies my left ear cannot hear anywhere near as well as my right ear. Fortunately with my EQ software, I can specify a different EQ curve for each ear, the L and R channels. The resulting EQ curves should turn out to be interesting.
That's no fun :O thank goodness for eq though >.>