Disclaimer: This IEM is owned by James. Measurement has been carried out at approximately 3 mm away from the reference plane, using a pair of stock bi-flange sleeves.
After a sudden discontinuation of their introductory model RE-0, HiFiMAN comes up with a new pair of IEMs, RE-400 Waterline, with a price tag of $99. And in order to reinforce their high end IEM line up, RE-262/272 are replaced with RE-600 Songbird. As HiFiMAN RE-262/272 have stunning electroacoustic characteristics, if RE-600 turns out to be as good, or even better, it will surely be considered as a very successful transition done by the manufacturer.
PRO: The titanium-coated driver brings down RE-600's distortion figure below the 0.1% threshold. Channel tracking is well-matched too.
CON: The tonality has become darker than that of RE-400, while the high frequency extension is now more conserved.
ON SECOND THOUGHT #1: Just like RE-400, this IEM becomes linear when it's fully inserted up to the reference plane. Indeed, this is not a good news for users with smaller ear canals, even though the IEM itself is quite compact.
ON SECOND THOUGHT #2: Applying additional acoustic impedance at the output of an IEM is a proven technique to control harshness. However, it is important to note that the frequency that is most affected by such damping is 5.5 kHz, at which a deep-null(anti-resonance) is located.
ON SECOND THOUGHT #3: Thanks to the diaphragm made of titanium, the frequency response of RE-600 is more dependent on the acoustic interaction of ear sleeves due to increased acoustic output impedance, thus choosing right sleeves is critical for optimal acoustic reproduction. Among three different types of stock sleeves, the sleeves with an obstruction at center of the bore, such as this one, perform the best. (I call them filtered sleeves)
ON SECOND THOUGHT #4: This IEM is ported at the bottom of the housing, and quite interestingly, the vent controls bass up to 5 dB, while dampening the response @ 2 kHz. FYI, reducing the size of the vent to a tiny pinhole gives a nice thumping sensation in the sub-bass range and more presence in the mid-range.
ON SECOND THOUGHT #5: Perceptive readers must have realized by now, that the default ear sleeve utilized here is different from what I used in my RE-400 analysis. Moreover, most of the textual information here is a simple copy & paste from my previous RE-400 analysis, and the IEM can still be described in great detail. Once both IEMs are in match with insertion depth and bore acoustics, the deviation falls within 4 dB from 2 kHz to 20 kHz range, which is simply derived from difference in voice coil configuration. Everything else is identical, even down to the very basic time-domain measurements.
RE-600 has been at the center of heavy debate and name-calling among users due to its suspected technological similarity with RE-400, whose price is exactly one fourth of RE-600's. If electroacoustic performance of RE-400 and RE-600 brothers is almost identical, how can the price difference of $300 possibly be justified?
ON SECOND THOUGHT #6: If any of the RE-400 users out there want to experience the sound of RE-600 without having to pay the quadruple amount of money you've already spent, here's a little trick for you: Simply insert a sheet of microfiber cloth between RE-400's nozzle and the sleeves, and RE-400's sound shall become pretty similar to that of RE-600. The result can't be identical, but why not give a shot when the mod is totally reversible & free.
ON SECOND THOUGHT #7: HiFiMAN RE-600 lacks substantial amount of treble compared to Harman International's hi-fidelity reference target.