Thanks to Thujone for sending these in. The HiFiMan HE-4 is sort of the oddball in the line. Few have it or have heard it. Essentially, it's a 5LE, but with magnets one on side instead of both. It's quite light - which is a change from the HFM 'phones which tend to weigh a tone. Unfortunately, the lighter weight of the HE-4 does make it any more comfortable. The top ridge of my head still hurts and the clamping force is still a bit too much.
Subjective Impressions (pre measurement):
Sort of light on its feet (very dextrous) and doesn't carry the bass weight of the HE-500 or HE-400. FR seems pretty even keel. Overall distortion seems lower than HE-400, however, there is some timbral weirdness in the treble which is sort of like an accentuated HE-400 treble or an IEM BA kind of quality. This is can both be a good a bad thing. Good in terms of definition, bad in terms or textural rendering. There appears to be slight dip in the mids around the female vocal harmonics region. Also some slight mid-treble brightness. I have mixed feelings about this one. While the overall FR seems good, the timbre is just too thin and the bass lacks authority. Quite resolving - moreso than HE-500.
In general, lower overall HD than HE-400 or HE-500 with exception of funky spikes in the R channel. Also notably high 3rd harmonic. Could this explain the BA quality of the sound? The 5k distortion spike is worrisome. Probably translates to possible 10k ringing and the timbral weirdness mentioned above. A lot more last octave air than the measurements would indicate.