Summary: First off, the only reason I rated 4 instead of 5 stars is because I had switch out the Sennheiser bud tips for my old Sony MDR-EX71s. The Sennheiser tips created an uncomfortable suction inside my ear canal.
Sound is awesome. I'd equate the bass to having a subwoofer in your mouth...but the full range is no punk either.
Summary: The sennheiser cx300 was my first headphone of Sennheiser and my first earbud/headphone above 30 Dollars. The construction of the earbud itself is very great and the design too, small, classic, lightweight. The cable is pretty flimsy in the jack i had 2 pair of cx300, and both goes this way.
In terms of sound, these deliver a outstanding, in your face bass. I have some issues with that because the mids are sucked out.
Pros: Loud, pretty easy to drive, Out of this world Bass, Comfy
Cons: Too much Bass, Sibilant/Harsh treble, Flimsy
Summary: I'm genuinely shocked that folks are unimpressed with these buds. They've served me very well for a looooong time. Yes, they handle bass veery well, but I never found that was at the expense of treble, not at the start (are now, since 4 years of earwax... yeh, you knowaddamean). Could be better isolating? Sure, but I regularly hear nothing of the outside world when I have them plugged, unless someone's near me.
Pros: Comfortable, decent sound, actually fit in my malshapen ears, pretty good drowning-out-of-world, longevity, cheap
Summary: These earphones, now the de facto first upgrade for an iPod, are alright if not unexciting. Compared to the stock iPod buds they're like hearing music for the first time again, but there are many other options which sound as good if not better. For my money, I would and do recommend Sony.
Summary: For a price this earphone has, it sounds great. A good bass response for something this small, and superb isolation from outside noise. Without music on, you can't barely hear anything else, as it doubles up as earplugs. But design wise, it should have a normal Y-shaped wire split to left and right earphones instead of going back 'round the neck. Just too messy. And the wire insulator material is to rubbery and grippy. But overall, the x-factor is the sound.
Summary: These earphones are really good. The sound is superb although it takes a bit of time to select the correct ear piece for each ear. Either they fall out or cannot be inserted properly. It may be me so cant blame the product. These are the second set I purchased as I mislaid the first, so have no hesitation in recommending them.