Summary: I read great reviews for these earphones but when I started testing them I felt cheated, the sound coming out from the earpieces was really tinny and a tad metallic, perhaps I didn't break them in but the small drive and lack of range was abysmal.
Pros: Not very expensive, an improvement from default earphones
Summary: So, the other reviews are fairly accurate. I bought (two pairs of them!) a while back and I thought they were good, Senheisser brand made me feel smart. If only I had come here first (or known about head-fi) I could have made a better decision. At $40 they're not worth it at all.
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.
Pros: Loud, pretty easy to drive, Out of this world Bass, Comfy
Cons: Too much Bass, Sibilant/Harsh treble, Flimsy
Summary: Bought these as a cheap iem to use while my customs are being fixed, they sound pretty good for the price, isolate well enough to be bearable on the train, and weren't too expensive.
My problems with them come from the entire design of both the iem's and the product as a whole.
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.
Summary: Having been a marketing casualty years ago by the Sennheiser headphone giant having two decent over-ear headphones bought of them, I decided to have these for an MP3 player additionally seeing good reviews about them.
Summary: I should disclose that I purchased these headphones for $15, and for that price I recommend that anyone snatch them up as a back up, or workout phones. However, not sure that I would purchase them for $60 or even $40.
Summary: Like many other people, I got my cx300's as they were widely available on the high street with not much competition at the time. They are mostly known for their bass which is very abundant. The problem with that much emphasis on bass is the rest of the range suffers.
Summary: Well worthwhile upgrade and not too expensive. Emphasized lower end.
My only complaint after using these for the gym for over a year now is that the cord length is different from the split to the buds.(one more than twice as long as the other)