Speaking of the effects of higher output impedance and how it affects the sound, e.g., makes it more sluggish, lush, organic, etc. I've attached two graphs showing the difference between 1.5 ohm and 51.5 ohm (close to the ME's ~45) output Z on a 500Hz square wave with the Grado HF-2.
It may be difficult to see at frist, but upon closer examination, we note the leading edges and peaks of the square waves are sharper, less blunted, and more delineated on the 1.5 ohm measurement. We also note that the 51.5 ohm measurement has more low amplitude swiggly stuff - the higher output Z amp will have a harder time controlling the driver in a precise way.
