The two best headphones I've got right now [for everything, BTW] are the AKG K371 and the Drop 6XX. Sub-bass insinuates bass that's lower than 20hz, but for most people it really means the bottom audible octave, 20hz to 40hz. The only headphones that I've got that deliver 20hz out of the box without eq are the AKGs, and they do it with very little power as well. The Drop 6XX [Sennheiser HD650 with a different paint job] require equalization, particularly in the bottom two octaves, and also require a fair amount of power to dig up that bass. That bottom octave is necessary for lots of "Classical" music, as far as I can tell a lot of "room tone" is down there. The AKG headphones are slightly less smooth in the top octaves compared to the 6XX 'phones, but at times that sounds more accurate/plausible to these ears than the ultra-smooth top of the Sennheiser 'phones. The treble presentation on the AKG 'phones seems to have more rosin on the bow. I can clearly hear the difference with "Original Instruments"/historically informed recordings like the Musica Antiqua Koln performance of Pachelbel's Canon or the Jordi Savall/Hesperion XX recording of François Couperin's Les Nations. There's a similar effect with massed strings, the Karajan/VPO recording of Beethoven's 7th Symphony displays the difference between the two headphones in the treble registers. There's rarely any 'grit' coming from the 6XX 'phones, sometimes it seems to be missing. However, the Drop 'phones have a more open sound, textures don't occlude, it's easy to follow all lines in polyphony. That deep bass comes in handy with organ recordings, but also lends more solidity to piano and orchestra as well. Both sets of headphones are excellent with vocal music, the AKG 'phones are a little bit more low-slung in that department. The AKG K371 headphones are going for $120 at B + H right now, a bargain and a great choice for phones and DAPs on account of their high sensitivity. However, though closed back, they don't isolate as much as other closed-back 'phones. The Drop 6XX are open backed and as I said before, require eq and additional power to perform at their best. The 6XX are regularly $220 but you'll probably need a headphone amp to get the most out of them. My Topping L30 [just got the replacement to deal with ESD issues] works great with the 6XX, the AKG K371 'phones don't really get much better with additional amplification. I've got 5 other sets of headphones, Sennheisers, AKG and Philips, none of them come close to the quality of the 6XX and K371.
