HiFiMAN RE-400 Waterline In-Ear Monitors (Earphones)

Introduction to the HiFiMAN RE-400 Waterline In-Ear Monitors

HiFiMAN unveiled the RE-400 Waterline In-Ear Monitors back in January at CES. Their goal was to set a new standard for high-performance, yet affordable, in-ear monitors and the name Waterline implies just that. With a low $99 price tag, that is not an easy goal to achieve.

Having reviewed both the HE-400 and HE-6/EF-6 HiFiMAN products, I am quite familiar with their work, and also quite the fan. Of course those models are both planar magnetic designs and have just about nothing in common with the RE-400’s.


  • Driver: 8.5mm Titanium Diaphragm
  • Impedance: 32 Ohms ± 3.2 Ohms
  • MFR: 15 Hz – 22 kHz
  • Sensitivity: 102dB/1mW
  • Rated Power: 10mW
  • Maximum Power: 30 mW
  • MSRP: $99 USD
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  • SECRETS Tags: HiFIMAN, Earphones, In-Ear, Audio
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Design of the HiFiMAN RE-400 Waterline In-Ear Monitors, In Use, and Rating

The RE-400’s design is conservative and simple. A silver aluminum shell houses the 8.5mm titanium driver and neodymium magnet. Those materials make the RE-400’s extremely light, to the point of almost disappearing in your ears. The weight of an IEM is crucial to its ability to both fit snuggly in the ear canal and remain comfortable and can make a huge difference in the overall enjoyment of an earbud. As soon as an earbud loses that quality seal, the low end response all but disappears and the sound becomes empty and shrill. To assist with that seal, I tried both the provided silicone tips as well as a pair of Comply foam tips. The seal with the foam tips was more comfortable and consistent along with providing better sound quality, so I stuck with those.

The cable has a tangle resistant fabric weave casing on the main section, and a smooth standard casing on the left and right split section. The rubbing of the cable against clothing conducted a bit of noise when exercising with the RE-400. I noticed the provided silicone tips conducted the most noise, while the foam tips dramatically reduced that noise.

The sound quality generated by the RE-400 Waterline’s was open, crisp, and neutral. There was no heavy or boomy low to mid-range, or overly bright treble. Bass response was quick and ample when I paired them with foam tips. With just the silicone tips, it was harder to achieve the right seal for proper bass performance. Bass nuts may want more low-end than the RE-400’s provide, but, for me, they sounded great.

I threw all types of music at the RE-400’s and they never missed a beat. Arcade Fire’s “Wake Up” has a lot going on and can sound like a muddy mess, but via the HiFiMAN’s it was rich and never fatiguing. The brass on the classic score to Conan the Barbarian by Basil Poledouris was slightly thin, but this is stretching to find a complaint about an in-ear-monitor with such amazing value. Woodwinds were incredibly clear and wispy. On the HD 24bit/192kHz 20th Anniversary Edition of Jurassic Park, the HiFiMAN RE-400 sounded airy, full-bodied, and neutral.

Moving over to something a little more taxing, I threw on the latest for Jay-Z, Magna Carta Holy Grail. The opening song “Holy Grail” was smooth and polite until Jay-Z takes over and the bass line kicks in and you realize these little guys have a bit of an attitude. The RE-400’s pump out the tunes with some aggression, playing both loud and clean. These IEM’s may not be the bass-lover’s dream, but they provided plenty of thumps for my tastes, all the while keeping a balance to the sonic spectrum. Like the other HiFiMAN products I have used, the RE-400 Waterline’s put the music first, before loudness and style.

In-ear monitors don’t exactly come in all shapes and sizes, but they do come in an incredible amount of flavors- from extremely cheap and poorly made to custom-molded, professional pieces. When people ask me for advice on what to purchase, I find it handy to have a few suggestions at different price levels. Up until now, I haven’t had an option under $100 that I was confident in recommending. Then along came the HiFiMAN RE-400 Waterline In-Ear Monitors at $99 thus filling that missing tier. I think one would have to spend close to twice as much to get something considerably better than the RE-400. The midrange is clear as day, neutral, and never empty or flavorless and, with some foam tips; you can enjoy plenty of tight, detailed bass. For a measly 99 bucks, you can start enjoying what it sounds like to have real depth to the music you listen too. You can start hearing a body behind the voice, a guitar behind the strum, and the breath controlling a woodwind- what being an audiophile is all about. I can’t think of a better in-ear monitor to start enjoying this hobby with. Another incredible product from HiFiMAN.

HiFiMAN RE-400 Waterline In-Ear Monitors Rating

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