Disclaimer: Finally I am completely done with Rick's headphones- Now I need to work on his IEMs. In less than few weeks, the current batch will be finished! :)
As previously verified with Audeze LCD-2 Rev.2 and Fostex T50RP, planar technology finds its versatility in a dipole driving mechanism. Due to less physical constraint given on the moving-mass, a planar headphone generally has low acoustic output impedance, low distortion, and wide frequency bandwidth.
Since HiFiMAN products usually exhibit an acceptable level of electroacoustic peformance, such as that of the classic RE-series IEMs, expectation is higher than ever.
CON: Inverted polarity!
ON SECOND THOUGHT #2: Above data clearly shows how uniformly HE500's driver behaves. However, when the microphone is positioned in the center, the characteristic deep-nulls, which can also be seen from my HATS data as well, appear.
ON SECOND THOUGHT #5: This is due to Rick's personal request. While Accudio™ certainly helps tame the peak and deep-null, the app makes the headphone sound little too bassy IMHO.