Let me start by saying these headphones surprised me. The Fostex T40RPmk3 arrived with that distinctive planar magnetic 'thwack' when you tap the earcups - a satisfying reminder of the tech inside. The closed-back design feels premium, though the stock pads? Absolute dealbreakers. My ears touched the drivers within minutes, creating this weird pressure point that made long sessions impossible.

Enter the $35 aftermarket pad swap (Dekoni hybrids in my case). Suddenly, these transformed into comfortable studio beasts. The Regular Phase technology shines when mixing - I could actually hear subtle reverb tails on vocal tracks that get lost in my M50Xs. That 20Hz-35kHz range isn't marketing fluff; during a bass-heavy synthwave session, I felt sub-bass textures rather than just hearing them.

But here's the twist no reviewer warned me about: the sound signature evolved dramatically over weeks. Initially crisp highs and tight bass gradually morphed into a mid-bass monstrosity. I now keep EQ permanently set to -5dB at 250Hz just to make them listenable. It's like they developed a personality disorder.

Power demands are no joke either. My Schiit Magni 3 Heresy at medium gain barely gets them to satisfying levels, while the same amp drives my Sundaras effortlessly. They're power vampires disguised as 50-ohm headphones.

Final verdict? At their best, these deliver astonishing detail retrieval for closed-backs... until they don't. Would I recommend them? Only to tinkerers willing to mod pads and wrestle with EQ daily. For plug-and-play reliability, save up for those Sonys.