Using a traditional rubber-tipped design, the Monster iSport Immersion earphones offer a reasonable level of noise isolation, physically blocking out the sound of the outside world. They're not the most aggressive isolators we've heard, giving a less vacuum-like seal than some competitors unless some extensive wiggling is done, but the level of noise reduction is easily enough to make listening while on the tube perfectly enjoyable. And as these buds are fairly bassy and powerful-sounding they have no trouble trampling over any remaining ambient sound.
They're much more accomplished than most sports headphones, which come second only to DJ headphones as purveyors of sonic compromise. It's worth considering when spending this much money on a sport earphone, though, that the noise isolation design isn't entirely helpful. Not only could it lead to you crossing the road mid-run into the path of an oncoming vehicle, whose driver's senses have been dulled by cataracts or Cinzano, it tends to emphasise other noise too.
The thud of your feet on the ground (it's especially bad when running across tarmac) and microphonic noise, created when the cable rubs against your clothing, means its worth considering a pair like the iGrado Street Style instead, or even the ultra-cheapie Koss KSC75. That said, up the volume a bit and wear the earphone cable under a layer of clothing to avoid impact and they'll perform well enough. Also, if you do make sure to look left, right and left again the noise isolation provided does allow you to listen at lower overall volume than more open-air earphones, saving your ears from damage - especially useful if you regularly run passed busy roads.
The sound signature is well-suited to exercise. It's punchy, with a strident bass presence that's surprisingly well-balanced - and honestly a whole lot of fun. The soundstage isn't as wide or as warm as the Bowers & Wilkins C5, which use a similar ear-hugging design, but the low-end is better-controlled here. You wouldn't guess to look at them, would you?
Give the Monster iSport earphones a beat to thump out and they'll keep you working out at the right pace with the ferocity of a 280lb drill instructor, without the awfulness that would involve. They're not massively high-fidelity earphones, though. The treble has a reasonable presence, but the top end is not as well-mannered and sweetly-resolved as we'd expect at the price. As such, they are prone to harshness at times.
The Monster iSport sound rather fab for sport headphones, but considering the fairly high price and the rose tint drains away from this picture. It's not just the sound, which is bags of fun but roundly beaten in the hi-fi stakes at the price, there's a design issue too. They just don't quite feel robust enough, given you're paying more than £100 for the set. Being able to stick them in the wash along with your sodden gym kit is a significant plus, but isn't something that we feel quite justifies such a premium.
Take the H2O Audio Surge earphones - they cost around £45 and offer the same level of waterproofing, and can be submerged in up to 3.6m of water. The Monster iSport may sound better, but when sport and hi-fi listening don't really mix, they're tough to recommend.
The Monster iSport Immerse sound rather great - for sports earphones. That's an important clarification, because if their waterproofing doesn't mean much to you, better sound is on offer for less money. However, their bassy sound is great fun and complements a workout well. The design is fairly comfortable too, although the lightweight build quality and easy-to-break in-ear stabilisers mean they don't feel like they're worth the asking price.