Review - FX Audio DR07

Review - Hifiman RE-400 (sub 50€)

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Also available on YouTube in Spanish: Acho Reviews YouTube 

Let me start out by saying that these IEMs were kindly sent to me by Hifiman for review. I am not receiving anything in exchange for this review, nor have I received any further requests from Hifiman.

I think I have already made it clear in previous reviews but I will say it again, this review is based on my own personal opinions and my aim is to be as sincere as possible, however, it did not cost me anything to be able to test these earphones. 


To be totally honest, I did not even know these IEMs existed until they were sent to me for review, therefore I had no idea what to expect. I did do a quick search online and saw that they are available from Hifiman for $29, which puts it in competition with lots of ultra budget IEMs and places it well inside the “sub 50€” category that I like to point out on this blog. 

I also saw that there are some reviews of the RE-400 stretching as far back as 2013, which means it has been around for quite a while. I didn’t actually read any of the reviews as I wanted to form my own opinion, seeing that I have received it without knowing anything about it, but I did notice that it was around $99 back then. 

So, how does the Hifiman RE-400 stack up against an infinite number of low cost IEMs that are available on the market?


The box that the IEMs come in is a rather thick perspex sleeve with an internal cardboard sleeve that pulls out from the bottom. On the face of the packaging is the Hifiman logo at the top, with “waterline” written directly underneath. I had absolutely no idea what “waterline” meant, nor why it was relevant, as I saw nothing related to water in the included booklet, however, after looking at Hifiman’s site, on the RE-400 page they have the following text:

The Theory of Wooden Bucket

Also known as Cannikin law, indicating that the chain is only as strong as the weakest link. The wooden buckets; capacity is determined by the shortest stave.

So, I think that “waterline” is referring to the capacity of a wooden bucket. I am not sure why this is relevant but I found it curious.

Inside the packaging we find the IEMs, two sizes of double flange tips, two sizes of silicone tips and the instruction booklet.

Another thing I found curious was that there was also a round IEM case included, which contained another selection of silicone tips and 10 replacement filters. This case was not included inside the actual packaging of the product (there is no room in the packaging for this) but was delivered together with it. I thought that it may be because it is a review unit but it seems that these are included as standard. Again, it is a strange choice to have them included separately but is a nice addition. A case and spare filters are not something you would usually receive with a $29 set of IEMs.

Build and comfort…

Let’s start with the negative part… the cable. The cable is not detachable and is a combination of fabric covered cable as far as the split and then individual cable from the split to the actual IEMs. The quality of the cable is not great and it keeps the shape of the folds it had when packaged. I also found that when wearing the IEMs with the cable down, it caused noise in the IEMs each time something brushed against it. However, wearing the IEMs with the cable up solved this issue. The cable also has a nice little chin slider which can come in handy.

On the positive side, the IEMs themselves are very small and compact, basically disappearing inside the ears as they are not much longer than the tips themselves. I don’t have a habit of sleeping while wearing IEMs (or listening to music) but I found that I can easily lay on my side while wearing them and not notice them at all. These are a great option for those that are looking for something comfortable to sleep in.

The shell of the IEM is completely made of metal and has a simple silver finish to it. There is a small vent located at the side of the cable entry.

Although the cable is not removable, there is at least some strain relief located at the IEM end of the cable. Ath the opposite end, the cable is terminated with a 90º 3.5mm TRS connector, which also has decent strain relief.

All in all, I have no complaints with the build, other than the cable, and due to their small size they will be comfortable for almost anybody (depending on tips used).


Over the past few years, IEM sound quality has been getting better and better, almost by the day, so I didn’t have high hopes for a $29 IEM that was released 7 years ago, even if they were more expensive back then.

However, I was pleasantly surprised to find that they were nowhere near as bad as I expected.

In the bass region, the RE-400 presents us with a tuning that is not like the usual tunings found in IEMs, especially in the lower price brackets.

There is no bass boost at all, which gives the impression of lacking in bass, and maybe so, but I was surprised to find when doing a tone test that I could easily hear all the way down to 30Hz. As there is no bass elevation at all, when listening to songs that depend upon bass, such as “Sun Is Shining” by Bob Marley and Robin Schulz, the IEMs leave us feeling that it is lacking in bass.

However, when listening to songs that aren´t depending on bass, such as the acoustic version of “Perfect” by Matt Johnson, you don’t get the feeling that bass is completely missing, just that it is not overly present.

Moving from the bass into the mids, again there is no elevation, presenting a very neutral transition. Sometimes this may cause the feeling that there is a little warmth and body missing from acoustic guitars or pianos. Saying that, the resulting sound is not horrible, just different from other sound signatures that I am used to. For example, in comparison to Hifiman’s own TWS600, which was also lacking in the bass department, I find that the RE-400 is far more pleasurable.

Moving into the higher mids, the first real elevation appears around 3kHz, which gives voices a lot of presence but manages to do so without becoming shouty. In fact, I found that the mids on the RE-400 are really rather nice. I find that most voices are well presented and nicely defined.

Up in the higher registries, there is a peak somewhere around the 6kHz region which actually manages to create a good sense of definition but manages to avoid sibilance. Above this point the highs start to roll off which avoids the IEMs being piercing for such a bass light signature, however, it also lacks “air” in the higher registries which would allow it to sound a little more open.

Speaking of openness, the width of the sound stage is not very big, in fact it is quite intimate, and the placement of images is not very precise. It does give you a general sense of location but not enough to pinpoint an image.

Definition and detail is not great, there are plenty of newer offerings that provide much more detail but we do need to consider the age of these IEMs. While I could easily tell the differences between similar instruments that are playing the same passages, it is not as easy to pick up on the nuances of the way the instruments are being played.


We live in a time when there are endless options in the low cost bracket of IEMs, some of which have amazing performance for their price. At the speed with which some chinese (and non-chinese) companies release new models, the RE-400 could be considered ancient. However, the fact that these IEMs are still selling, even if they are at a very reduced price, is one way of saying that they are something that has held up pretty well over the years where others have just disappeared off the map.

The RE-400 are certainly not amazing IEMs but nor are they offensive, I have heard much worse that has been released lately, admittedly not from brands with a name like Hifiman.

The overall sound signature to me is reminiscent of the Tin T2, with less definition but with better mids and less fatiguing in the higher registries. I would even say that they don’t roll off as much in the bass as the T2.

While I wouldn’t consider them a fun sound signature, I do actually find them a pleasant sound signature and would love to hear the same tuning with more detail and better overall.

They won’t be making it to the top of the sub 50€ list, however, they do place themselves above many other IEMs that I have tried. For an IEM that is over 7 years old, that is not bad at all.

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