In-ear headphones can come in all sorts of shapes and sizes but the basic technology behind them can be broken down into two groups; those that use moving-coil (dynamic) drivers and those that use balanced armatures. Now, I won't go into the intricacies of what the differences between the two types are, for that you can pop along to wikipedia, which has a good explanation.
In summary, though, balanced armature drivers are easy to make small without losing accuracy/quality but they naturally have a narrower frequency response and require a better seal to deliver their full potential. This is why the best headphones use dual and triple driver configurations and also why these often have to be inserted unnervingly far into the ear-canal to get the best from them.
Dynamic drivers, on the other hand, can cope much better with the full frequency range and require less of a seal to get the best from them but they're also inherently larger. There are also tonal differences but I'll come to those later. For now, let's get to the guts of this review.
The Sennheiser IE8 earphones, then, use a single moving-coil driver in each earpiece. Sennheiser claims this one driver is enough to compete with the best dual and triple balanced armature driver headphones made by the likes of Ultimate Ears and Shure. Considering both the Shure SE530s (E500 as was) and Ultimate Ears triple.fi 10 Pros cost only marginally more but have proved themselves to be truly outstanding earphones, the IE8s certainly have a lot to live up to.
Upon arrival the IE8s make a good impression with a rather stylish case opening to reveal the earphones all neatly laid out along with plenty of accessories. Unfortunately, it quickly becomes apparent the packaging and accessories resemble a case of style over substance.
The carry case is a peculiar two piece affair with a slide out insert that the earphones wrap around and an outer protective sleeve. Now, it isn't inherently difficult to nestle the drivers in their foam homes and wrap the excess cable but it is most definitely pointless, as are the holders for spare tips. This is supposed to be the place you store your earphones for use everyday, so why on earth would you constantly want four spare tips with you?
Then there's the fact the case leaves no room to store miscellaneous accessories like an airline adapter or 3.5mm to 6mm jack adapter (not that you get any of these in the box). As I've said before, a simple zip up case with an internal pocket for whatever accessories you want is all that's needed.