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H2O Audio Flex

H2O Audio Flex Review

H2O Audio Flex
Reviewed Jan 2011

Details: Entry-level waterproof earphones from H2O Audio
MSRP: $29.99 (manufacturer’s page)
Current Price: $20 from
Specs: Driver: Dynamic | Imp: 16Ω | Sens: N/A | Freq: 20-20k Hz | Cable: 3.9’ L-plug
Nozzle Size: 4.5mm | Preferred tips: stock single-flanges
Wear Style: Straight down or over-the-ear

Accessories (1/5) – Single-flange silicone tips (3 sizes) & H2O SealTight adapter (for use with H2O Audio waterproof mp3 player cases)
Build Quality (3.5/5) – The colorful shells of the Flex are made entirely out of plastic but feel quite solid overall. The cable entry point is protected by a flexible rubber sleeve and the strain relief on the angled 3.5mm stereo plug is one of the most impressive I’ve seen on an entry-level earphone. The cable itself, however, is a real letdown – far too thin for my liking and very rubbery compared to that of the higher-end Surge. On the upside, the Flex is waterproof. I can’t say how long the earphones will last with constant underwater use but for the occasional sweaty workout they should work just fine
Isolation (3/5) – Quite decent due to small housings and thicker silicone tips
Microphonics (3/5) – Bothersome with cable-down wear but easily tolerable when worn cord-up
Comfort (4.5/5) – The plastic shells of the Flex are small and exceptionally light. The spherical shape allows for very comfortable fitment with the right tips and I’ve even managed to sleep in them with no discomfort whatsoever

Sound (5.9/10) – H2O Audio’s original waterproof IEM, the Surge, surprised me last year with the likeable and reasonably refined sound produced by its waterproof transducers. The new Flex is just as impressive, pursuing a sound signature rarely found among budget-level earphones – one that is balanced and spacious rather than intimate and bass-heavy. The bass of the Flex is easily the most mundane aspect of its sound signature – controlled and fairly accurate but lacking in depth and impact. The Flex, with its slight mid-bass boost and fair amount of roll-off, is definitely not one for the basshead but for those who prefer a more balanced sound the low-end response should be adequate.

The midrange of the earphone is more impressive – free of bass bleed and surprisingly clear. As with the Surge, the transducers of the Flex aren’t the quickest in existence and as a result detail and texture lag slightly behind most mid-range earphones but the impressive clarity makes up for it. Compared to the de-emphasized bass and treble of the Flex, the midrange is slightly forward though it can seem distant when compared to the more intimate-sounding earphones usually found in the entry-level price bracket. The smoothness and laid-back presentation make the sound of the Flex quite likable and easy-going – good traits for an exercise earphone to have. Sibilance and harshness are absent from the lower treble response but a bit of treble sparkle is present nonetheless. Treble clarity and detail are both reasonably good in the context of the smooth sound signature and extension is decent as well.

It is the sonic presentation of the Flex, however, that is most interesting – the soundstage is wide and extends farther in every direction than with most other entry-level earphones. The space is relatively spherical in nature and positioning is quite convincing on the whole. Layering and separation are lacking slightly and the Flex isn’t as adept at separating a track’s background and foreground as most higher-end sets but for a $30 earphone the presentation is very impressive nonetheless. Aside from the aging Soundmagic PL30, really aren’t any entry-level earphones out there with the spaciousness and airiness of the Flex – and that alone makes it worth the asking price.

Value (8/10) – The Flex may not be particularly pretty, well-built, or well-accessorized, but it does several things very well – it is extremely comfortable, sounds surprisingly good, and shrugs off water and sweat. While those in search of deep, thumping bass will be unimpressed, the Flex can match far pricier models when it comes to clarity and space. Will it survive daily underwater use as advertised? I really don’t know, but there are (pricier) waterproof sets that are likely better-suited for the purpose. However, as a reasonably-priced everyday earphone for music and movies that can also survive a sweaty workout, the Flex very difficult to beat.

Pros: Lightweight and comfortable; Water- and sweat-proof; Balanced, spacious, and surprisingly refined sound
Cons: Not much in the way of pack-ins; Rubbery cable can be noisy; Bass lacks depth and rumble





Living in the fast-paced city of Los Angeles, ljokerl has been using portable audio gear to deal with lengthy commutes for the better part of a decade. He spends much of his time listening to music and occasionally writes portable audio reviews across several enthusiast sites, focusing mostly on in-ear earphones.


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