HiFiMAN RE-0

I thank my dear friend, Bryan, aka Gnarlsagan, for providing me with an opportunity to analyze this nice piece of IEM.

Originally priced at $79, HiFiMAN RE-0 is a budget IEM, known to outperform some of the top-notch IEMs in the market. While other high-end products of the brand, such as RE-262 and RE-272, are finely engineered to meet the general criteria of Hi-Fidelity in headphones, it is considered that RE-0 also comes very close.

PRO: Overall very linear. Distortion-free. Left & right channel matching is excellent. Due to its linear, yet high impedance value, it is almost impossible to alter the sound of RE-0 electrically.

CON: Slightly peaky in the upper frequency range due to resonances.

ON SECOND THOUGHT #1: Surprisingly, RE-0 is precisely engineered to be shallow-inserted. Once it is inserted too deep(at the reference plane) or too shallow(just blocking the ear canal), the response above 10 kHz loses linearity.

ON SECOND THOUGHT #2: Due to resonant peaks in the high frequency range, it is a good idea to apply multiple layers of the stock damper, preferably more than two plies. It is, however, important to note that the treble response drops gradually as the number of dampers increases.

ON SECOND THOUGHT #3: Stock single sleeves yield the most linear response.

ON SECOND THOUGHT #4: There are two acoustic vents on RE-0. Considering the left channel unit only, while the vent on the left only works as a depressurizer, the right one equalizes the mid frequency range up to 4 dB. I would only use the right one if I were to make a tonal change.