Out of box they sounded very good, FAR better than other similar $ headphones. I would not say "hi-fi" but WAY better sound definition than most headphones under $100. They are not bass-heavy, rattle your noggin cans. They are more in the lane of "reference" or neutral. I thought they had slightly forward highs, occasionally sibilant, perhaps ... but that's a big word and hardly fair for headphones we paid <$40 for!!! Bass was there and controlled but recessed a bit on some tracks I listened to. For example, a cello won't sound booming, but will sound very real, and right there. For classical or critical listening, that's great; if you want to feel the bass from pop, R&B etc in your gut, these aren't for that. If you can afford over $80, sure, there are better options for critical listening, for example Phillips 9500 which are an amazing deal for the price, and you can sometimes score an audiotechnica M40 on sale or refurb for just a bit more.My son bought these to replace some skull candy and originally missed the bass those had. But, over a couple weeks he says the superlux are so much clearer, cleaner, and spacious sounding, he doesn't like the skull candy anymore. He says he can hear all sorts of detail in music he never heard before (and he likes it...). My experience lines up with that from the few tracks I listened to with these (though I don't put his skull candy on my head ... ever). Everyone will be different.... so look up more details elsewhere. But $ for sound, these surprized me in a really good way.Build quality doesn't look exceptional. They don't look fragile, just like they are "just adequate" and not more. My son usually tears things up pretty quick, headphones not withstanding. Hence he paid for these himself ... 2 pairs from dad in <2years and you're on your own, Jack. So far, a couple months of frequent use (he uses them every day, several hours per day ... some days I think he has these on more than he doesn't) and they are holding up okay.My son listens to them with a generic MP3 player and they sound fine, so no amp needed ... but if you add a little juice, they do perk up and shine. But so do most good headphones. I let him listen to these on a class A solid state and then a tube headphone amp, and his jaw dropped. He tried his skull candy on those and went "meh, yeah, better, but ... not like the superlux" The point is, these are surprisingly good headphones for "cricial listening" if it's not blasphemy to say such about a sub $50 headphone, but you get out of them what you put into them. On a marginal source, you may not notice a big difference between these and a typical $40 set but as the source improves, they start to really separate from other similar priced cans.Be aware, if you aren't familiar with semi-open/ open, that means they leak sound - in and out. You can still hear things around you AND others can hear YOUR music even if it's not cranked up. The tradeoff is, again if you are not aware, is that the design makes them sound really spacious. Open/semi-open headphones are rarely this cheap, so in case you wondered into reviews of this Superlux looking for a "cheap but decent" pair of cans to wear on the train while commuting ... hmmm ... think on that a bit.I have a lot of far better headphones ... but for the money, I've not heard anything this "good." It looks like these bounce up and down in price. If these were $70 you could do better for a couple bucks more and would be well to do so (phillips 9500 again). We scored these for less than $40. At that price I'd buy them again any day!! 5 stars for VERY good sound at a CRAZY, CRAZY low price. If $50, I'd say 4 stars because there are other competitors at that price that have better build quality better comfort, and better sound. Hit $75 and I'd drop to 3 stars - too close to Phillips, Sennheisser, and Audiotechnica options that edge these out.