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.
The HD 218i is a semi-collapsible plastic set of phones that comes with an in-line mic and remote control for the iPhone. The remote comes with a volume up/down button and single play/answer button. We like the position of the mic — it's close enough that you don't need to scoop it up to your mouth so callers can hear you. While you can use the headphones with an Android phone, only the play button works, and plugging the headset into a PC means a bit of jiggling with the plug to get it to work.
The headphones are padded with a leatherette material, which feels quite plush when placed on your head. For over-ear phones the leatherette does a remarkably good job of blocking out extraneous noise, though it won't do much to block out rumbling plane engines.
Having had bad experiences with poor bass response before we were actually blown away by how good the HD 218i sounded. The sound was rich and well balanced for the headphone's relatively small size. It wasn't muddy, "one note" bass, but relatively deep sounding and articulate. High frequencies were also in order, with plenty of detail in voices, though cymbals were a little recessed. The soundstage was deep, and we were surprised how "hi-fi" such an entry-level headset could sound.
The only potential issues we have are the headset's high price — the microphone adds an extra AU$40 to the price! — and the plastic-y quality of the rotating ear cups. If you want to save some money, and don't need the remote or mic, go for the HD 218s instead. However, if you're looking for a great-sounding, iPhone-specific headphone we don't know of any that perform this well for the price.