Strong bass without being muddy
Separate volume control
Cons:Large ear canals required
The Bottom Line: You can buy better from Sennheiser, but these take the cake for the price point (around A$35-40 retail).
I purchased these to replace my generic earbuds that came with my MP3 player (and what MP3 player doesn't come with a substandard pair!). Purchased for the Sennheiser name and also previous positive experiences with Sennheiser products. These aren't the best in the lineup, but for A$35 couldn't be beaten. Quite bassy, but without being muddy. Designed for larger ear canals, which isn't a problem for me, but my mother finds them uncomfortable to wear (she has a set of the CX300s and they are great for her, but more expensive). Listening to hard rock and metal primarily, they serve the purpose very well, and expose poor MP3 encoding quality (anything below 160kbps you can tell sounds lacking).
Recommend this product?
Some modification of the EQ is required, they sound a little flat by default, but only a minor adjustment is required (once again surprising for the price point targeted). Some slight augmentation of the bass is all that's needed, not too much or they can sound muddy.
They are also incredibly robust, surviving a trip halfway around the world and back, plus constantly getting unintentionally abused from being crushed, and being a cat toy (my cat loves them!), and no signs of aging as yet. Highly recommended.