HIFIMAN RE400 Waterline Review: This in-ear monitoring from HIFIMAN is the budget level below $100 earphones. The RE400 has gone some improvement over the years and can be considered as a mature product.

Instead of throwing a crazy number of drivers like KZ, HIFIMAN keeps focusing on the small enclosure and a single driver. It’s important to know that the number of the driver doesn’t mean that the quality will be better than a fewer driver.

The model name made me think, “Waterline” according to Oxford Dictionary: “The level normally reached by the water on the side of a ship” with my interpretation I think HIFIMAN would like to tell us that the HIFIMAN RE400 could deliver a sound that provides a balance.


RE400 Waterline has a simple yet appealing packaging with the frosted transparent plastic cover.

At the front packaging, HIFIMAN is highlighting the strength: ergonomics, 8.5mm titanium-coated diaphragm, neodymium magnet, oxygen-free copper cabling and something that I didn’t know before that the driver is manufactured by HIFIMAN itself.

Sliding it down, you can see the drivers are fitted in nicely and pretty secured. Apart from that, you can see a couple of ear tips, putting the large double flange tips in the middle is weird, it’s not the best placement in terms of design in my opinion.

What’s included?

  • 3 pair of silicone double flange ear tips
  • 2 pair of black Silicone ear tips
  • 3 pair of white Silicone ear tips
  • Replacement Filters
  • Shirt clip
  • Carrying case


  • Driver: Single Dynamic Driver
  • Impedance: 32 Ohms
  • Sensitivity: 102 dB
  • Frequency response: 15 Hz – 22 KHz
  • Cable Length: 1.33 mm
  • Plug: L Shaped 3.5 mm


The selection of the double flange ear tips is interesting, it really fits the design of the housing which needs a deep penetration to the ear canal. 

Filters replacement is a very welcome accessory. I can’t find in the user guide on how to replace the filter, a simple instruction here would be helpful. 

The non-detachable cable is thin with a plastic coating. Interestingly after the Y split, the cable has a braided coating. I’m a little bit worried about the cables, first: it’s thin and you need to handle it a little bit with care. Second: because it’s non-detachable, once you have an issue with the cable and that’s the end of the story. 

Considering the asking price at 39 USD, I will let it pass with a non-detachable cable. I feel that I’m asking too much at this price even though ChiFi IEM in this price region is offering a detachable cable. 

The 3.5mm L-shaped jack is sturdy and the strain relief is well designed making the connection point secure. the cable is flexible, light and there is no memory retention on the cable even though you can wear it over the ear. 

Microphonics is a little bit a problem here, I can still hear sound transferred to the earphone from touching or manipulating the cable, not so evident with the braided cable on the lower part. 


The RE400 designed like a small bullet-shaped earphone. the earphone is very light, the lightest that I’ve ever touch so far. you can see a similar design from Etymotic and Final Audio.

The build quality is good, housing is from aluminum. The tiny design will make the earphone go deep inside your ear canal and it will help you to get better isolation and a good fit. it’s lightweight and comfortable for long use.

There some simple strain relief on the termination point between the cable and casing. You’ll see a clear marking on the side with the letter R and L. You can wear them like normal earphones straight down or over the ear like In-ear monitoring, If it’s comfortable I would suggest to wear it over the ear because it will help to reduce the microphonics effect.

RE400 has a standard Nozzle opening at 0.5mm and it’s easy to take out and put in tips because of the lip on the nozzle that will hold secure the tips.

Inside the nozzle, you can see the black filter and as mentioned before, the additional filters to replace them will be very useful down the road. Request: Please add some guide on how to do the replacement or video 🙂



Sub-bass a little bit is hidden and buried. Overall the bass has a quick decay. there’s not so much punch and impact here but the bass is present. Listening to Raven – GoGo Penguin, I would say the bass is a little bit flat without a good texturing.


The mids are smooth and the voices are a little bit laid back. Both male and female voices are rendered nicely. Listening Just give me a reason – Pink, Nate Ruess, I feel that the mid is a little bit recessed.


The treble has a good sparkle without going over to the sibilance area. overall it’s balanced and has a little bit of boost. RE400 has good detail in the treble area, listen to the Train Song – Holly Cole I assure you that those ring and bell at the background is very vivid.

Soundstage and Spatial

The soundstage is in the middle point, it doesn’t extend too much and it’s not to narrow either. There’s enough air in between to separate the instrument, but it will hit the limit when hearing music that has more complexity with a lot of instruments and demanding.


Overall the HIFIMAN RE400 has a natural sound signature with a little bit emphasized on the treble side. The bass is not that great and some will find this lacking but taking consideration about the sound signature and what HIFIMAN trying to achieve it’s understandable. The treble details are great and I don’t expect that in this price range.

With the current discounted price at USD 39 (was USD 79), it has the sweet spot between performance and value, even though when listening to the song you’ll find it kind of lack of energy but after all it’s a natural sounding IEM.

If there’s one thing to improve, perhaps its the cable. I find that the cable is too thin and could easily tear.

The RE400 is a perfect replacement for your default earphone that comes with your phone. This is also for people who are looking at something different more a reference sound: natural and lean sound.

You can purchase the RE400 from HIFIMAN main website (free shipping) or AMAZON

If you are interested on the True Wireless Earphone instead, HIFIMAN has one! you can read the review here: HIFIMAN TWS 600 Review

  • ACCESSORIES - 8/10
  • BUILD - 6.5/10
  • BASS - 7.5/10
  • MIDRANGE - 8/10
  • TREBLE - 9/10


Overall the HIFIMAN RE400 has a natural sound signature with a little bit emphasized on the treble side. The bass is not that great and some will find this lacking but taking consideration about the sound signature and what HIFIMAN trying to achieve it’s understandable. The treble details are great and I don’t expect that in this price range.


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