Hello,
 
Quick thoughts on modded with bass mod sennheiser hd 439.
 
Build quality
 
It is a mixed bag really. Headphones it self feels cheap. Well, probably because it is cheap. But they don't feel cheap then you have them on a head. They are very comfy, velour pads fit my ears perfectly. I forget I have headphones on my head the moment I put them on. Although if you have big ears, it could become an on ear headphones, because pads are not very big. Design is nice to my eyes, but you know, it can look bad for you
 
Audio quality
 
I'm reviewing modded headphones with bass mod, so keep that in mind. The sound they make is really quite good. Bass goes very very deep. For tracks like royksopp - the drug it just blew my mind . I listened to it with my sens 518 and it just uncomparable. 439 destroys 518 in a bass heavy music. So if you are into music like this - go get it, do the mod and enjoy your music like you never did before. As for more popular music. They are actually not that bad. Sound stage is pretty good, but of course not as wide as 518 as they are opened. Still instrumental separation is good, you will here instruments in their place and not a chocolate mix  . Vocals. Hmmmm, well you can  hear them . Really not much more to say about them. You will not be blown away by them, when you listen to dido or meja. If you into female vocalist, when these headphones not really for you. Rock music is in a middle between bass heavy and female music. Lets say rise againts sounds good to my ears. As I said above, instruments are nicely separated but vocals are just where. So overall these headphones are perfect for a bit more bass heavy music, but not for "audiophile" stuff.
 
Important note
 
I don't why, but I find them very hard to drive. No joke, even though they are only 32 ohm, I find them a lot harder to drive than 518 which is 50 ohm. I don't know if it is just me, but I go to an 8 (max with low gain) with my fiio e10 and I keep 5 when I listen to 518. When I travel, I use my ps vita as a player and it does good job powering it (better than fiio e10 ). As for ****y samsung android phone, it goes to listenable levels, but you can hear it struggles with headphones and ps vita just destroys it. I listen for few tracks on a phone for a review and just couldn't continue - it sounds terrible. So keep that in mind if you planing on using it with your ****y phone  I don't about iphone or such. Probably it will sound as good as ps vita which sounds pretty nice.
 
Conclusion
 
For the price these are very nice headphone and actually holds up pretty good versus its big brothers. Beats them in low end but gets beat in mids and highs. As I said, I would recommend them for bassheads and such. As for pop music, I don't really listen to it. As I said, dido don't sound so good, but listenable, I will not call it terrible as my phone experience. Beyonce actually sounds good to my ears, low end gives a very lively sound. Of course beyonce itself have powerful voice. Well I took a hit for you dear reader and listened to katy perry's roar and it sounds pretty bad ( but it could be just katy perry ). So yeah, I guess I gave you a pretty good understanding what to expect for these headphones. Cheers.
 
P.S.
 
I forgot to talk about isolation. It will muffle the sounds around you and if you are on a bus or train really you will hear just a distant wheel and engine sound, nothing to worry about, you will be able to enjoy your music. But they leak. I will get looks at bus if I put sound on higher volume. So keep that in mind.

Hello,
 
I would like to share my impressions of my first a bit more decent headphones - Sennheiser HD-518. I'm no audiophile, so this review will be more for a "normal" people, who want to use it not just for music, but for games and movies too.
 
Build quality and design
 
  Headphones is all plastic, so no suprises where. It have strange grills that could look a bit silly, but hey, you will not go out with them outside. You could and I did it few times, but cable is just too long, you end up in wire mess + headphones are open, so no isolation from outside noise, you just don't enjoy your music with these outside.
  Pads are made just for me. They just perfect, they are a bit stiff, but this is what i like, you can wear them for hours and just forgot you have headphones on your head. I usually listening for music while I'm laying in bed, no problem with these being on your head ( I fall a sleep few times with headphones still on my head, glad didn't brake them ). They fall few times from a table, still in one peace. They are ready for some brutal force.
  Cable. Cable is long, 3m to be exact. I can walk around in my room with no problems at all, and I live in not that small of a room. I can see having a problem using a laptop, but these are perfect for a stationary pc use.
 
Audio Quality
 
  I must say, then I first heard hd 518, I thougt I just wasted my money. They sounded dirty and kinda bad. I was disappointed. But I read about burn in thing, so I said I give them a chance. And my God they sound wonderful now. I had quite a journey these headphones, so read on if you wanna know that a life changing journey I had. I will talk about music, games and movies.
  Music. As they advertise, sennheisers have deep bass. And yes, yes they have. The bass is thigt and pretty bad ass. If you looking just for a bass, look elsewhere, at closed headphones, because the bass is there it should and is not overwhelming. After going to sens from closed headphones it was strange at first, but i'm loving it now, it is big then should be, like in electromusic, but then listening to AC/DC for example, it doesn't overwhelm other instruments. Lets say bass knows its place . The soundstage is big and wide, if you wanna know that people talking about, then they talking about soundstage, listen for these headphones . But it took headphones(or me to get use to the soundstage) to open up, because just recently I started to enjoy my music in all different way. It was quite an exiting journey too, to rediscover all the music for the third time. As good as these headphones sound in a music department, then we talking about instruments, but they have one big flaw for me, and it is vocals. To describe how vocals sound in hd 518, it will be if the band is all in one room with you and singer is behind the wall singing. It sounds a bit distant, a bit too quite, sometimes hard to understand. I guess you can fix it with a EQ, but I had no luck. Everything else changed in these headphones dramatically from a day I bough it, but vocals stayed the same way, distant, and a bit hard to listen to. I read few other reviews saying the same, so it is not just me.
  Games. Games sound wondifirus. You can hear everything around you. In skyrim I never got attacked from a back. With these your oponents don't have a chance to attack you from behind. Explosions in company of hereos sounds powerful(deep) and i will never getting tired to listen to machine guns shooting at enemies. So for games, I say YES to HD 518. But keep in my mind it is not a gaming headset, if you looking just for it, look at gaming companies like razor or such. Games sound good and open design helps a lot, but I imagine on dedicated headphones it will sound even better.
  Movies. Strangly enough, I don't have any problems with actors sounding bad, as singers sound in music. You can hear everything. I mean I watched scott pilgrim vs the world for the 5th time with these. I can say it was like I watching it for the first time. So many things I missed just because I watched it with cheap headphones. You can hear everything clearly, every little sound Edgar Wright placed in where. And now, with new XBMC Frodo realese and new audio-engine, that reproduce 5.1 surround in a way it should sound and opened soundstage of sens, I can hear everything so clearly it makes me cry .  While watching transformes I could pin point from that side every explosion coming from and it really makes you appreciate sound in movies. For movies these headphones gets a HELL YES from me.
 
Conclusions
 
It was a great jorney with sennheisers and now, then they reached the point of a maximum performance(if not, edit is coming), they are just amazingly amazing. Yes, these are my first mid-fi headphones, not even high-fi, but I'm guessing I will not change my headphones for a long long time. So if you are like me, want a great quality and don't wanna cancel your christmas, get these and don't look back. For a closer, I will say a quote that made me buy these: " If you wanna buy high-fi headphones just because they are high-fi and you really don't know that are you going to do with them, don't waste your money and just buy sennheiser hd 518". Quote might not me that accurate 
 
EDIT 2013-07-20
 
So I ended up the university and now I can delete my windows partition and use linux all time ( damn you ms office). So I had a time to play with sound of my sennheiser in linux and pulse audio is a bitch. But then you get it right, YOU GET IT RIGHT. And guest what? They sound even better than they sounded on windows. MUCH better. In  a bass department they now have a real "oouf" in their sound, you can feel it. It is pretty nice. While watching Dark knight rises I felt like in a cinema. For a moment I was afraid drivers might explode. As for my biggest complain with singers voices, it is finally fixed. Voices of singers doesn't sound behind and distant, they feel closer more intimate and smoother sounding it just flows now.. Finally i can enjoy my favorite female singers voices from metric to the cardigans. So i guess the conclusion is it wasn't headphone fault, but windows fault . And other conclusion would be, that these headphones is very sensetive to source and equalizing. You need to really play with them do get the best out of it. I'm planing on upgrading my creative card to asus ST, so another edit might be coming in maybe three-four month, depending on how my budget will be
 
EDIT 2014-03-04
 
So instead of asus ST I get  a fiio e10. First impressions - not a big difference from creative sound card. BUT when I think to myself, that I equalized my creative sound card to "perfection", so I should do the same for my fiio 10. So I did. Soundstage opened up and got even wider, vocals got a bit foward and sounds very clean, bass tightened up ( I use bass boost on fiio e10). Without mentioned changes, sound itself that e10 reproduce is very clean, probably because it is far from computer hardware which created a small hiz when listening to my creative card. Also, it is now powered properly.  Sound card really struggled to power 518, I had almost always to set volume to max. Now it is around 5 on e10 and 50 proc. on my volume in OS and it is very noticeable. It is hard to explain, but it gives a life to headphones and also to music. It sound more lively. If you feel your sound card struggles to power sens 518, you have your volume in windows, mac or linux set up high, I will recommend you to upgrade to e10. If not, well if you expect to be blown away by an dedicated amp vs your sound card, it is not going to happen. It will sound a bit better, but not "OMG AMAZING" better