The AKG K420 headphones sound nice. They are great if you want, or need high fidelity, semi-open, portable phones. I hate closed phones. The K420(s) sound like my AKG K240 MKII(s), if I were to boost the lows & highs on them a little bit The lows are deep and tight on the 420s. Kick drum and floor toms sound great! The highs are nice, except at very loud SPL listening levels, where at that point, they get a little harsh I use the 420s, for portable use, at mostly low to mid SPL listening levels. At low volume, upright bass sounds great, losing "some" definition at louder SPLs. At lower volume levels, The mild rise in the Hi and Low end frequency response is nice, ...sort of like hitting the "loudness button" on an old stereo, to compensate for the Fletcher-Munson curves of human hearing response at low SPL(s). A lot of listeners, would love them at loud sound levels.
When I go loud, at home, my go-to, is my K240MKII(s)
At home, I also listen to K240 sextetts and Sennheiser HD 414s.