Koss is one of the oldest headphone makers in the US, and it has a number of models that have remained in the line for decades. I'm thinking about theheadphones and the headphones, to name two.
So when Koss introduces new models I'm all ears. The SP330 on-ear and SP540 over-the-ear headphones sport a fresh look, and I think they're quite handsome. Both headphones come with zippered carry cases that do an unusually good job protecting the headphones. Both headphones have 52 inch long user-replaceable cables, and both lack mic/remotes for phones. They're 35 Ohm impedance designs.
The SP330 ($129.99) on-ear is smaller and lighter than the SP540 ($149.99) over-the-ear headphone. The sound is open and very clear, the SP330 is one of those headphones that really grew on me. Bass was nice and full, but never thick, dynamic contrasts were lively. Vocals are immediate and very present, highs are a tiny bit rough, but certainly on target for a headphone in the SP330's price class. The soft ear pads were fairly comfy, but I would have preferred slightly lighter pressure against my ears. The SP330 folds flat for compact storage, and I liked that the ear cups are reinforced with anodized aluminum.
Moving onto the SP540 over-the-ear headphone there's a sizable increase in bass, and the "D-profile" memory foam cushions more closely follow the contours of human ears than more typical round or oval ear pads. I found the SP540 more comfortable than the SP330, but that's true for a lot of over-the-ears, for me. The SP540 also features outer ear cups reinforced with anodized aluminum, and the headphone folds flat for storage.
I liked the SP540's sound, but it has a tendency to veer to overly rich; then again, some listeners might like that extra fullness. As always, that's a subjective call. Audio Technica's ATH-M50x headphone's tauter bass definition is more my taste and it sounds more accurate overall, compared with the SP540.
When I settled in with the SP540 I appreciated the sound balance, especially the way it tamed some of the harshness associated with heavily compressed recordings. With those recordings I preferred the SP540 over the ATH-M50x.
Regarding Koss' lifetime warranty, it works like this: if the headphone breaks the company will repair or replace it for the original owner. You return the broken SP330 or SP540 to Koss with a check for $6, and that's it. I've known people who bought a Koss Porta Pro on-ear headphone 20 years ago, and have had the headphones replaced a number of times. When Koss says lifetime, they mean it (if your model is discontinued you get an equivalent replacement).
So if you're rough on headphones, and Koss' are extremely well built and come with a lifetime warranty, what could be better than that?