HifiMan HE6SE

The Hifiman HE6SE are a much awaited (perhaps, even much needed) follow-up to the former HE6, orthodynamic darling that was in production some years ago and which, along with the first Aude’ze models, marked the renaissance of orthodynamic headphones in the commercial audio production.
The HE6 had great qualities, coming from a very large, powerful driver, and associated to the inherent capabilities of orthodynamic headphones to react to tuning (using felt and other materials inside cups, to remove resonances / play with reflections, in order to tweak bass and high frequencies).
The HE6 have gone out of production several years ago and have been missed by the community.

The HE6SE are more expensive than the original HE6 (1800 usd vs 1300), but they pack several improvements. While they retail the same driver, they have better, much less resonant cups than the original model, which required modifications in order to remove bass resonance. The new stock pads are also much better (same pads that come with Hifiman Sundara), with angled orientation, more capable in controlling treble.
Finally, the new headband is sturdier and more elegant.

While some people still consider necessary to perform some minor modifications to the HE6SE (mostly, removing the grill from the cups, as some think it adds ringing at high frequencies), I did not detect this issue during my listening and I have decided to leave them stock.

Frequency Response : 8Hz to 65 KHz
Impedance : 50 Ohm
Efficiency : 83.5 dB
Weight : 470 g

The H6SE have extremely low efficiency and very low impedance, thus, a speaker amplifier is advised for them, and is likely to be a better match than a headphone amp. Usage of a speaker amp is even encouraged by the presence of an adapter box, that comes with the headphone.
Test System

DAC: Custom dual channel AK399 DAC with Museatex mods
Preamp: Pass Labs Bride of Zen
Power amp: Pass Labs Aleph J (MOSFET amplifier)

I have connected the HE6SE directly to the Pass Labs Aleph J, using an XLR-to-speaker out cable adapter, which should provided a purer connection than using the stock adapter box.
To me, the HE6SE is a very special sounding headphone. It is a headphone with huge authority, earth trembling and precise bass. It sounds like it’s coming from something very big, and it’s the best, most realistic bass I have heard in a headphone. It’s super special and it is what made this headphone so loved in the past.
The HE6SE have a forward sound signature. It pushes some sections of the midrange and treble department which result in an “exciting” headphone, slightly tilted towards a lively, enraged signature. They always push forward, give an “on stage” feel to the sound, and at the same time manage to be rooted to their bass foundation.
It’s like the best possible evolution of a Grado RS1. The balance produced is very involving, toe tapping, energic.
Compared to the Susvara, the HE6SE are more of an active performer, while the Susvara are more tonally transparent. The Susvara is lush and full, where the HE6SE is more exciting and aggressive. The HE6SE work very well for rock, metal, jazz, while the Susvara is a better all arounder, and definitely works better with classical music.
The HE6SE, though, has an edge in bass slam, bass effortlessness, violence.
Treble is not sibilant, it does not have any metallicness, but, as said, along with upper midrange, it impacts the music in the way at an interpretation level interpreted. Vocals are very emotional, intimate, with a trace of “nervousness”. The same “emotional amplification” is applied to the rendition of electric guitars.
As expectable by such technically capable headphones, the sound is always highly detailed, textured, very tactile. Instruments are placed precisely and with high definition in the soundstage.
Bottom Line

This headphone is very lovely and special for me, although perhaps not as smooth as other headphones like Susvara, Stax L300 Ltd, or Hifiman Shangri-La Jr. It is quite unique because of its incredible bass, involving signature, emotional rendition.
The bass, especially, creates addiction! Seriously, it is really difficult to find in something like this in a headphone. It is solid, it has immense authority, it never sounds underwhelming.
While it is possible to fiddle with the internals (playing around with felt or other materials), in my opinion, the HE6SE can be enjoyed immensely in stock form, provided enough power is supplied to them. This is their main caveat, because they could easily underperform with the wrong amplification (the web is full of discussions on that note), while they deserve lots of power in order to shine.