When it comes to buying headphones it seems there are two choices: Sennheiser and everyone else. Sennheiser has so many models to choose from, though, that it can be hard to pick one. While models such as the open PX100s are fantastic, the company has had a chequered history when it comes to closed portables in particular. For example, the old PX200's are one of the thinnest sounding models we can recall hearing.
The HD 218i is a set of closed headphones that attempts to get high-quality bass response from a closed, portable design — not an easy task.