First review but here goes 
The Sennheiser HD 558 comes with a 3m detachable cable, a 6.5mm to 3.5mm converter and the headphones themselves.
Comfort and Build: Although the headphones themselves are made entirely of plastic it doesn’t feel like the cheap plastic. In fact the build seems solid enough to take light abuse but I really wouldn’t recommend anyone stress test these to any high extent. They do however feel like a well-constructed pair of headphones. In the comfort department it feels light on the head with heavy padding on the headband and thick padding on the ear cups. Both quite soft but the cloth material is a dust magnet. Even within a day of use you can sort of already see the dust being picked up by the pads. I guess it might just be my room that’s extremely dusty but just thought I’d give a heads up. Also right out of the box the clamping force is quite high although they aren’t horrendously tight (they are in fact extremely comfortable) they don’t feel like the clamping feeling around your ears are going to disappear anytime soon. Because of this my ears do get quite warm over a period of time. However that being said it does mean that when adjusted correctly there is almost no feeling on the top of the head. The cable isn’t all that special, it’s pretty thick but isn’t overly stiff terminating at a thick and chunky jack. Strain relief on both ends of the cable are more than adequate.
Sound
Bass: I wouldn’t consider myself a basshead but having a bass presence and that low rumble or pounding always helps in finding the beat of a piece. In this case you can hear the bass of a song with some bass presence but the thump really isn’t all that impressive. It’s there but it isn’t going to knock you out if that’s what you’re into. There is some rumbling when there isn’t much else in the track otherwise it just gets trampled over but mids and highs and you really have to concentrate to notice the full effects and rumbling of the bass. There just seems to be a slight lack of overall tightness in the bass, in some passages it just feels a little muddy with some bleeding into the lower mids when there is just a stampede of sound with . All in all I find the bass somewhat sufficient for me, but I would prefer to have slightly more tightness in this area for cleaner sound.
Mids: Ahhhh the mids, so smooth and relaxed. They never feel harsh or obtrusive, taking a more relaxed tone that is sweet and lilting. Lower strings and guitar are clear and feel extremely laid back with a light airy sound. Cellos feel just as how I feel a cello should sound for more calming pieces with viscosity and a slight warmth to them that just give you the feels inside. Male vocals are a tin bit veiled and lacking in weight and power, it seems as if they are TOO polite. This is absolutely fine for slower and more relaxing songs but when they need it for that powerful tenor sound I find a generally lacking. Female vocals are so wonderful to listen with that silky smooth flow of voices. Again however the voices are almost too polite for some songs. It’s just too rounded and relaxed it lacks the bite or attack in their voices. This is not dissimilar to the headphone in general, there just doesn’t feel like there is any bite to the sound whether it be strings or voices. This is perfect for lyrically emphasized songs and jazz that require a warm velvet sound that just allows you to relax and have a good lie down.
Highs: The smoothness of the mids carry over into the high range allowing for longer listening periods that have a ton of high frequency sounds. There is plenty of treble sparkle without a lack of thickness. I wouldn’t say that the highs are thick like the mids but rather there is a good balance between the two. Neither is really fighting to overcome each other and I find a good balance of the two ranges. That being said the upper registers of violins and voice are again smoothed over. There is also a sense of clarity and breathiness which make the highs all the more enjoyable. The airiness and smoothness reduces the harsh sibilance allowing in longer listening periods. It isn’t totally smoothed however and you’ll be glad to know that there remains a slight edge to the sharpness of the highs. Giving back the bite to strings which sometimes is just so crucial to make the sound much more intense than if it was totally smoothed over.
Clarity/Soundstage: The soundstage feels large but you will never feel that you are sitting in a concert hall. It feels more like you are sitting in a largish room. It’s certainly big enough but I don’t feel that I’m really suitable commenting too much as I’ve been pretty much using IEMs only so these are a vast improvement. Due to the larger soundstage, open feeling and breathing room between the instruments and vocals it takes a large step up in the clarity and also transparency. I can hear the subtle snapping of fingers or the light thud of a piano pedal in the recording in comparison to my IEMs which masked these tiny details.
Overview
For the price I paid (around $160US) I find these headphones a nice deal. It’s generally pretty comfortable (although clamping is pretty damn high >.>) and delivers a warmer, pleasing sound to slow relaxing songs like jazz and vocals but because of this it just doesn’t really have the power or bite that sometimes just makes you go WOW at the performer. The light airy sound help with relieving congestion overall, but it just really isn’t suited for intricate bass pieces as it just becomes slightly muddy even though there isn’t that much thump or rumbling. Furthermore the bass department just doesn’t have the emphasis to satisfy some users. If bass is the sole thing you are looking for in a pair of headphones maybe try to avoid these? But in my opinion this isn’t too much of a problem to me, what is the problem however is how Sennheiser decided it would be an absolutely marvelous idea to terminate the cable in a 6.5mm plug. This makes the plug freakishly long and it is a good 9cm in length when you add the converter t-.-t (like why?!). Luckily you can buy replaceable cables online so just a temporary setback although I would really have just preferred a 3.5mm jack and a converter. Another thing you should consider when buy these is the level of isolation or sound leakage. Due to the open design it doesn’t block out a noisy environment particularly well and if you raise the volume too loud be prepared to share your music with the outside world.
The Sennheiser HD 558 comes with a 3m detachable cable, a 6.5mm to 3.5mm converter and the headphones themselves.
Comfort and Build: Although the headphones themselves are made entirely of plastic it doesn’t feel like the cheap plastic. In fact the build seems solid enough to take light abuse but I really wouldn’t recommend anyone stress test these to any high extent. They do however feel like a well-constructed pair of headphones. In the comfort department it feels light on the head with heavy padding on the headband and thick padding on the ear cups. Both quite soft but the cloth material is a dust magnet. Even within a day of use you can sort of already see the dust being picked up by the pads. I guess it might just be my room that’s extremely dusty but just thought I’d give a heads up. Also right out of the box the clamping force is quite high although they aren’t horrendously tight (they are in fact extremely comfortable) they don’t feel like the clamping feeling around your ears are going to disappear anytime soon. Because of this my ears do get quite warm over a period of time. However that being said it does mean that when adjusted correctly there is almost no feeling on the top of the head. The cable isn’t all that special, it’s pretty thick but isn’t overly stiff terminating at a thick and chunky jack. Strain relief on both ends of the cable are more than adequate.
Sound
Bass: I wouldn’t consider myself a basshead but having a bass presence and that low rumble or pounding always helps in finding the beat of a piece. In this case you can hear the bass of a song with some bass presence but the thump really isn’t all that impressive. It’s there but it isn’t going to knock you out if that’s what you’re into. There is some rumbling when there isn’t much else in the track otherwise it just gets trampled over but mids and highs and you really have to concentrate to notice the full effects and rumbling of the bass. There just seems to be a slight lack of overall tightness in the bass, in some passages it just feels a little muddy with some bleeding into the lower mids when there is just a stampede of sound with . All in all I find the bass somewhat sufficient for me, but I would prefer to have slightly more tightness in this area for cleaner sound.
Mids: Ahhhh the mids, so smooth and relaxed. They never feel harsh or obtrusive, taking a more relaxed tone that is sweet and lilting. Lower strings and guitar are clear and feel extremely laid back with a light airy sound. Cellos feel just as how I feel a cello should sound for more calming pieces with viscosity and a slight warmth to them that just give you the feels inside. Male vocals are a tin bit veiled and lacking in weight and power, it seems as if they are TOO polite. This is absolutely fine for slower and more relaxing songs but when they need it for that powerful tenor sound I find a generally lacking. Female vocals are so wonderful to listen with that silky smooth flow of voices. Again however the voices are almost too polite for some songs. It’s just too rounded and relaxed it lacks the bite or attack in their voices. This is not dissimilar to the headphone in general, there just doesn’t feel like there is any bite to the sound whether it be strings or voices. This is perfect for lyrically emphasized songs and jazz that require a warm velvet sound that just allows you to relax and have a good lie down.
Highs: The smoothness of the mids carry over into the high range allowing for longer listening periods that have a ton of high frequency sounds. There is plenty of treble sparkle without a lack of thickness. I wouldn’t say that the highs are thick like the mids but rather there is a good balance between the two. Neither is really fighting to overcome each other and I find a good balance of the two ranges. That being said the upper registers of violins and voice are again smoothed over. There is also a sense of clarity and breathiness which make the highs all the more enjoyable. The airiness and smoothness reduces the harsh sibilance allowing in longer listening periods. It isn’t totally smoothed however and you’ll be glad to know that there remains a slight edge to the sharpness of the highs. Giving back the bite to strings which sometimes is just so crucial to make the sound much more intense than if it was totally smoothed over.
Clarity/Soundstage: The soundstage feels large but you will never feel that you are sitting in a concert hall. It feels more like you are sitting in a largish room. It’s certainly big enough but I don’t feel that I’m really suitable commenting too much as I’ve been pretty much using IEMs only so these are a vast improvement. Due to the larger soundstage, open feeling and breathing room between the instruments and vocals it takes a large step up in the clarity and also transparency. I can hear the subtle snapping of fingers or the light thud of a piano pedal in the recording in comparison to my IEMs which masked these tiny details.
Overview
For the price I paid (around $160US) I find these headphones a nice deal. It’s generally pretty comfortable (although clamping is pretty damn high >.>) and delivers a warmer, pleasing sound to slow relaxing songs like jazz and vocals but because of this it just doesn’t really have the power or bite that sometimes just makes you go WOW at the performer. The light airy sound help with relieving congestion overall, but it just really isn’t suited for intricate bass pieces as it just becomes slightly muddy even though there isn’t that much thump or rumbling. Furthermore the bass department just doesn’t have the emphasis to satisfy some users. If bass is the sole thing you are looking for in a pair of headphones maybe try to avoid these? But in my opinion this isn’t too much of a problem to me, what is the problem however is how Sennheiser decided it would be an absolutely marvelous idea to terminate the cable in a 6.5mm plug. This makes the plug freakishly long and it is a good 9cm in length when you add the converter t-.-t (like why?!). Luckily you can buy replaceable cables online so just a temporary setback although I would really have just preferred a 3.5mm jack and a converter. Another thing you should consider when buy these is the level of isolation or sound leakage. Due to the open design it doesn’t block out a noisy environment particularly well and if you raise the volume too loud be prepared to share your music with the outside world.
