With the Spritzer plug adapter, I auditioned my Monolith electrostatic with both of my Stax amps (SRM1-MK2 Pro recapped & SRM-353X). Using very familiar true hi-res music from AIX through my Oppo UDP-205, I could not even tell that there was a bass player in the mix, and the high-frequency hand percussion was nearly inaudible. My Koss ESP/950 with plug adapter on the same amplifiers clearly reproduces those two frequency extremes. (My Stax SR-007MK2 and Sennheiser HE 60 with adapter sound even better, but it is not a fair comparison in terms of price.) The Monolith M1060 planar headset reproduces the full frequency spectrum much better than the Monolith ES. And for dynamic driver models, my AKG K1000 also reproduces the missing bass and percussion (again, not a fair comparison pricewise) and the Sennheiser HD 600 and 650 (and 58X Jubilee at $170) have a more satisfying overall frequency balance than the Monolith ES. So I returned them to Monoprice because, for me, a midrange-centric headset is not worth $250.