The Sennheiser IE8i's sound signature is defined by the dynamic drivers used. It's warm and bassy, and not what we usually expect from a pair of earphones costing around £200. Up on the high-end shelf, earphones tend to become terribly serious, obsessing over accuracy and fidelity. Not so here.
However, these aren't the bullish dynamic earphones you'll find for less cash - these are probably the best dynamic driver IEM earphones in the world.
They have the voluminous bass recognised as a feature of dynamic earphones, but it's taut, deep and as well-behaved as a diplomat. But it's a diplomat who's always ready to become the life and soul of the party. While this warm, bassy sound signature is a good catch-all approach to take at the low end of the earphone market, it's more of a risk here up top.
It's the opposite of what's traditionally linked to the "audiophile" tone expected at this price. In order to combat this, Sennheiser incorporated the user-customisable bass dial, which sits on the outer edge of each earpiece. The dial is turned using a tool included as part of the package, and it subtly turns up the bass response.
After some experimentation with various bass levels, we found the lowest setting to be the best, most balanced option. It supplies the powerful sound that's the staple of these earphones without letting the low-end dominate.
Quite what magic Sennheiser has weaved to keep such a healthy low-end swell in-check within a pair of single-driver earphones remains something of a mystery, but it's helped by the unusually wide soundstage. This provides excellent separation and a wonderful sense of space within complex arrangements that's very rare in a bass-heavy earphone. This is truly one of just a few bass-crazy IEMs that will satisfy audio snobs.
Greater treble insight can be found in the more traditional multi-balanced-armature brigade, such as the Ultimate Ears Triple.Fi 10, but there's little point in chasing the Sennheiser IE8i from the start unless big bass is high on your priority list. We've criticised Skullcandy-toting bass hunters in our reviews in the past, but the IE8i earphones' stellar bass deserves no detractors. The effect it has on the super-low frequencies of dubstep tracks is particularly praise-worthy - it's scarily good - but it comes in handy with all genres because it's kept in check.
The upgrade the Sennheiser IE8i offer over the previous IE8 model, reviewed back in 2009, is the on-cable hands-free microphone and remote control. It allows you to take calls while these earphones are jammed in your ears, as well as changing tracks and volume when listening to music. This housing adds around £20-25 to the retail price, compared with the IE8.
At £200, the Sennheiser IE8i sit alongside the Ultimate Ears Triple fi 10 and Shure SE425. Each has a different character - the Shure SE425 middy and mature, the Triple fi bright and fun, and the IE8i are bass-pump pioneers. Crucially though, they perform around the same level. This feat is all the more impressive when you consider the Sennheisers are powered by a single driver, while the Ultimate Ears earphones use three a piece.
The Sennheiser IE8i show that earphones don't need six drivers to produce great sound. Using dynamic drivers, the low-end is more prominent here than in almost all pairs available at a similar price, but the quality of bass here is alarmingly good. It's deep, taut and thoroughly exciting.
If you want an analytical, bright or completely neutral pair of earphones, you're looking in the wrong place. But if your discerning ears are after a good time, you can't go far wrong here.