Disclaimer: This is owned by a mutual friend of mine. Measurement was carried out at 3 mm away from the reference plane using a pair of stock single flange sleeves.
Along with its low-impedance sibling, RE-272, HiFiMAN RE-262 has been known for its superb sound quality. Now their successors, RE-400 & RE-600, have proven to be rather a disappointment, it is perhaps a good idea to look back and check what's changed from the past. Have the current RE-models really devolved?
CON: The tonality is slightly dark with an audible peak at 1.7 kHz.
ON SECOND THOUGHT #3: Unless extra harshness in the mid-range & less amount of bass are desired, the vent must be kept open at all times.
ON SECOND THOUGHT #4: Here's a simple showdown among RE-0, RE-262, RE-272, RE-400 and RE-600, with their measurement condition equally matched. While the deviation between RE-400 and RE-600 is only a simple treble cut of -4 dB above 2 kHz, RE-262 and RE-272 have totally different resonant characteristics.
ON SECOND THOUGHT #5: Indeed, RE-262 & RE-272 are still as good as current RE-models, if not better, in terms of electroacoustic performance. However, once compensated by using Harman's Hi-Fi reference, the current models turn out to be slightly flatter than their predecessors.