Performance

Testing earphones is a very hard thing to do because you cannot run them through a series of benchmarks that will give you a valid result. In order to test the earphones I used them both with my three headphone amplifiers and just straight out of my Cowon iAudio i7 DAP.
Since these earphones have an impedance of 150 Ohms they are extremely hard to drive. This means that you need a headphone amplifier to get them to perform their very best. My home amplifier and DAC is an Octavart "The One" which is a class A biased headphone amplifier with internal DAC. Besides that I have both a HeadRoom Total BitHead and a Go-Vibe V6 which are two very basic portable amps. I will be using the following in-ears for reference purposes: LiveWires T1, Klipsch Image, Head-Direct RE2, Sleek-Audio SA6, Westone UM2.

Getting a good seal was easy due to the new bi-flange tips. They do feel a bit different to have in your ears than most of my other tips, but they are still extremely comfortable due to the fact that they are incredibly soft and do not exert that much force on the ear canal. It was actually a bit odd at first inserting them because they are bigger and softer than my other tips. I did a quick comparison to my Ultimate Ears foam tips and the bass is a bit bigger and a bit deeper with the new silicone tips of the RE1s. This is quite remarkable because it does so without sacrificing any detail. This just proves the importance of having good tips on your in-ears.

To begin with I hooked them up to my Octavart AMP & DAC by using the extension cable and a 1/8" to 1/4" adapter. And the sound was pretty neat, just like with the RE2s I had burned them in for around 50 hours before hand. I did a quick listen the moment I got them and the treble was definitely a bit harsher and the bottom end a bit more restrained. To get the volume to be audible I had to turn my amp volume knob to about 1/8 or 1/10 of its full capacity. With most in-ears that would have result in either an extremely high volume or busted driver, but the RE1s are different in that sense. The fact that they are way harder to drive means that you have to turn up the volume knob to get the same sound pressure quite a lot in comparison to normal IEMs to get matched volume levels. After a fair amount of burn-in it was almost as if the frequency had leveled out a bit more.

With all things adjusted properly I fired up Foobar 2000 and played some of my favorite tracks. The first thing that struck me was how neutral these in-ears sounded. No part of the spectrum is suppressed nor raised which makes them sound quite well balanced. This faithful reproduction makes them sound quite incredible on well mastered tracks. Compared to the Klipsch Images these are more cold and analytical and have a more aggressive and fast sound to them. The reproduction of the kick drums and the likes is extremely good on these in-ears, they pack a lot of punch. The bass is tight and well defined, amount wise there is a bit less than my LiveWires or RE2s for that matter, but the definition is remarkable and so is the extension which I find better than all my other in-ears.

The really deep tones are well represented on the RE1s when being fed by a good amp. I tried swapping back and forth between the Total BitHead and the Octavart and it is clear that these in-ears scale really well with the amp used. The Total BitHead was alright with the RE1s and so was the Go-Vibe V6. They were definitely a huge improvement in comparison to just running the RE1s straight off my Cowon DAP, however, using the Go-Vibe V6 inflated the bass a bit and made it a bit muddier to listen to, but still nothing horrible.

The Head-Direct RE1s really excel when amped, the transition from just being run off a normal powerful DAP to a decent home amp makes a huge difference. The bass goes way deeper and becomes tighter and more refined. Almost the exact same thing goes for the highs. Being fed by my Cowon the sound quality was severely crippled, the bass was less than desired and they lacked punch and just overall definition, however, as you hook them up to an amp they almost magically transform into great performing in-ears.

These earphones are power hungry little things and they simply crave a good amp. I am sure you will be able to find a lot of good amps that mate well with the RE1s. Their performance was exquisite while running them off my home amp since they sound so lush and smooth. The bass extension was extreme and the highs were just spot on, great definition without sounding harsh or too aggressive. The treble was extremely good and well defined, it is almost as good as that on my Sleek-Audio SA6s, but lacks a bit of sparkle and intensity. There is no doubt the treble response is incredible smooth and provides a lot of detail even when compared to earphones such as the SA6s.

The RE1s are fast and with a good and airy representation of vocals and feature a good sound stage for an IEM. Their sound quality is way better than the Sleek-Audio SA6s and Klipsch Images when backed by a good amp. This is not cheap and not portable so it kind of defies the purpose of in-ears. Their performance is definitely better than the other high-end universal earphones, but that is only when they are being fed by a good headphone amplifier.

Noise attenuation has gotten a lot better since I last reviewed a pair of Head-Direct earphones. This is because of the new bi-flange silicone tips. These provide a tighter and more comfortable seal than any of the other tips I have tried on them. They match the shape and size of the body better meaning that a good fit is much easier to obtain. Microphonics is still a little problematic with the RE1s, but nothing horrible. They are not the best and certainly not the worst when it comes to the amount of microphonic noise being transmitted from the cable to the ear piece.

Durability

The Head-Direct earphones are quite durable right from the mini jack to the earphones themselves. The body of these in-ears is well thought out and the build quality and finish are really good. The main construction is made of three pieces of plastic and the bond between them is rock solid. The plastic is hard and feels quite durable. The only thing that I can imagine being worn down over time are the gold details, but even those are well made and the color does not rub off easily, not even when scraping against it with a hard object.