Pros: Nice texture in mids to highs. Decent price. Exciting studio performance headphone.
Cons: Weak plastic build. Plastic components in ear cups will wear out, snowballing into further damage. Extremely bright.
I see a lot of reviews on here saying that they are "super smooth" in the mid range... Well I will tell you, the mid range is very interesting on these headphones... But it is definitely harsh. I always need to roll the volume back to accommodate this one peak in the mid range which dominates the spectrum. Don't get me wrong, they sound very exciting and fun to listen to, especially for music with reverbs. They show up due to the brightness. Bass is lacking, as is obviously inherent in using the term "bright". The best impression I can give is that they have a sort of "analog drive" to them which is very 70's sounding, and the I have a feeling that the mark 1's would have the better, more pleasing version of this. What I am saying is that in this sort of bright classic sound, an older original pair would hopefully not have the sort of sterility of a modern pair.
I believe these were originally found in studios for musicians to perform with, and that makes sense, because they are very "exciting" sounding... They make your performance sound a bit more golden. DEFINITELY not neutral, as some reviewers have been saying. Neutrality to me would mean that each instrument coming through the speakers would be indiscernible from the actual real-life instrument. A truly neutral pair of headphones would give the impression that musicians were performing in the same room as you. This is not the case with the K240's. Physically, they are very comfortable but sound-wise, they could hurt your ears easily at. They are probably some of the more fatiguing headphones out there. That being said, even after 5 years of use I am finally putting them through an intentional burn-in period of loud use in hopes of softening them up.
Another consideration is their structural build... You would think that the headband would be a hollow tube with a wire through it, connecting the two earpieces... This is not the case. The headband itself acts as the bridge between speakers. The speakers are soldered to each end. At each cup, the headband splits open in sort of a "Y", which rests in a little plastic bed, and gets clamped in position between the speaker and the little round plastic piece with the logo on it. On the ends of this "Y" are the speaker connections, soldered. Don't get me wrong, I think the headband is really cool and a brilliant bit of design, if I can say that prefaced with the fact that I do not have a broad idea of what is "good" design - the headband is not actually in itself at fault. The problem is that the wire connections WILL break with use. The plastic beds on the "Y" will crack from twisting, leaving the cups to twist a little more than they should. When they bust loose like this, it leaves the extremely thin wires inside prone to constant bending and eventual snapping. I had to fix mine by taking them apart, gorilla gluing the plastic pieces back together, leaving it for 24 hours, then soldering the connections back on. It's just a design flaw which I encountered after about 5 years of ownership.
Hope this serves as a cautionary tale. By all means, I encourage you to buy these headphones, because they are a lot of fun, have an interesting sound, and will give you years of enjoyment. Not to mention being a staple in recording studios. I am just saying, make sure to send your warranty card in, because with this design, it is only a matter of time before the damage I mentioned becomes present. Thanks for reading.