Again, my friend borrowed my Abyss to compare to his headphone collection.
He affirmed my opinion that other dynamic/planar headphones are in different league, can't compare to quality of Abyss and SR-009 at all even they were upgraded to very expensive cables .
The sources are AURALiC VEGA DAC and Ayre QB9 DSD. He used Leben CS600 as amplifier for electrostatic headphone via electrostatic converter and using adapter for dynamic headphone to connect Abyss to binding post of CS600 for better power. This means this comparison is quite fair using the same amplifier.
Bass of Abyss is superb, bested all the headphone in the market substantially. This can be called perfect bass, deep, rich, compact, detailed and it's placed in another layer than mid. As well as depth that is second to none, far better than king of sound stage headphone like HD800, SR-009 or even HE-90 (as recalled memory). Tonal balance is very good and quite natural sound signature using tube amplifier. My opinion is if it's paired with solid state amp (I tested with BHA-1) it's a little bit too bright. Details and clarity of SR-009 are still better than Abyss.
The cons of Abyss for him is look and comfortable. He doesn't like external design of Abyss at all. And actually it's quite comfortable headphone even though it's very heavy but still can't against SR-009, HD800 or Fostex TH-900 in term of this.