Don't let the ohmage fool you. 300ohms yes, but the sensitivity is 102dB/V, it's quite easy to drive since it's high impedance because the voltage will drop to the 800 even with lots of output impedance of the source.
I think generally, people look at ohmage in the 100's and think wow it a big value. HE-6 is only 50ohms, and needs considerable current because it's not so sensitive.
Edited by SilverEars - 7/20/14 at 4:21pm