Not sure how close the sennheiser hd555s are to the 558, but with the 555, there is hardly any bass, and unless I turn up the bass in the audio control panel (using a audigy 2 ZS) many explosions in games like warframe, left 4 dead 2, firefall, battlefield 4, crysis 3, and half life 2 death match, sound pretty tinny. but once you adjust the equalizer, they get a bit better, but I have been unable to adjust them enough to get a really good deep bass rumble from explosions like my old sony MDR xd-400's were able to do with no adjustment at all. (for those, the bass was not overpowered at all but when a bass sound required a deep rumble, they did it enough that you could get the bass sensation in the upper part of your body.
for an example of the type of rumble that I am talking about, play this song (skip to about 15 seconds) http://www.youtube.com/watch?v=jdaZ8_xfTUU (pretty much a bass test primarily designed for subwoofers, but does well on headphones)
It has a low bass note, and at an even lower frequency. (basically the main bass notes vary from 25hz, to 40hz, then at around 10-15hz there is a lower bass rumble that really contributes to the sensation you feel when the note is played. in many of the games such as battlefield 4, they make use of them also but the hd555 never reproduces them unless the equalizer is tunes to bring out more of the bass. (I wish I could get headphones that could give the bass of the sony mdr -xd400, and the mids and highs of the sennheiser hd 555)
with open headphones you still end up with like 95%+ of the volume going you you and not outside. You would have to be blasting audio at some very unsafe listening levels for people to hear it outside of the room, especially if the door is closed.
Edited by Razor512 - 12/2/13 at 12:55pm