Although it's adept with video, music is where the Cowon X7's forte lies. It handles a variety of formats including FLAC, APE and OGG alongside the standard MP3, WMA and WAVE, and sound quality is great. Next to our test iPod Classic 160GB, the Cowon X7 offers a more detailed mid-range on standard settings, giving vocals a more defined sense of texture, and greater presence.
If you're thinking of buying this player primarily on the merits of its sound quality, make sure you have a decent set of earphones already - you'll hear more of a difference upgrading from a £15 set of buds to a £50 set of IEM earphones than from a less capable MP3 player to this. If you already have a setup to do it justice though, the Cowon X7's JetEffect 3.0 engine offers a great way to tweak your sound.
JetEffect 3.0 is comprised of an EQ, an aural exciter, bass booster and a handful of other processing effects. It comes with a huge 35 presets, plus four that you can customise manually. And there's a whole lot of customisation to be done.
There's a 5-band EQ, each working to a /-12dB scale that you set manually. You also set the frequency for each of these bands, and whether they're wide or narrow in their effect. This EQ feature is unusually flexible and powerful, and even when taken to extreme settings didn't cause distortion. It's versatile and subtle enough to let you mitigate for the shortcomings of your headphones or earphones, which most media player equalisers simply aren't sophisticated enough to do.
Less time-consuming are JetEffect 3.0's BBE and Mach3Bass frequency boosters. BBE enhances the high-end subtly, increasing clarity without adding sibilance - although it may introduce harshness and sibilance when using very bright-sounding headphones. Mach3Bass is a similarly intelligent bass boost, although as it's quite powerful you can leave your music sounding like a boomy mess if you overdo it.
Used in tandem with the EQ, Mach3Bass can effectively sculpt the bottom-end entirely, which is impressive. We managed to turn an high-quality but overly bassy pair of buds into a restrained pair by severely restricting bass at 80Hz, then upping the Mach3Bass to replace it. The effect was surprisingly convincing.
These are JetEffect 3.0's best bits, and audio nuts will be able to spend hours fiddling with the EQ to get cymbals splashing as they desire, but there are a few extras too. 3D Surround fiddles with channels to give the impression of a wider, more dynamic stereo image. MP Enhance is designed to mitigate for low-quality digital audio files, but makes little difference to decent-quality MP3s. STE (Stereo Enhance) is a much less invasive alternative to 3D Surround, but therefore also much more usable. The final feature, reverb, won't be of much use when playing music, but you may want to add some to soften recordings made using the built-in mic.
All told, this may be the best-sounding hard drive MP3 player on the market. Anywhere.