HiFiMAN RE-262 and RE-272 In-Ear Headphones Measurements
With the exception of the significantly different impedance (262=140 Ohms, 272=20 Ohms), measurements of these two headphones bear a strong family resemblance.
Unlike most dynamic in-ear headphones---which usually have a fairly strongly rising bass---both the RE-262 and RE-272 have a very flat frequency response below about 800Hz. Above 800Hz, both headphones have a moderate rise in the presence region at 2kHz, with the 272 showing slightly more emphasis than the 262. The response on both fall after 2kHz at a rate that I'd consider slightly too extreme, with the 272 about 3dB higher in treble energy than the 262. The modestly higher amount of energy in the 272 over the 262 at 800Hz and above correlate well with ljokerl's listening experience. The peak at 8kHz is likely ear canal resonance and is a common artifact with most headphones.
30Hz square-wave response has good shape and is indicative of tight bass response, as is the THD+noise plot that shows no rise in distortion in the low frequencies.
Both headphones show an increase in distortion (THD+noise) through the mid-range on the 100dB SPL plot which may indicate some difficulty playing loud, but the 90dB plot show a fairly distortion-free headphone.
The 300Hz square-wave shows some significant ringing, and the impulse response of both cans are fairly clean, but look a little slow to me. I have to say, however, that both cans did sound quite good to me, so I'm not quite sure what to think about these two measurements. The 272 does look a little faster overall, which matches up quite well with ljokerl's listening experience.
Isolation is good at about 27dB broadband, but not at the level of some balanced armature IEMs. The RE-262 requires 43mVrms to reach 90dB SPL, the RE-272 29mVrms making it the slightly louder headphone. Both would work well with portable players, but the 20 Ohm impedance of the RE-272 does seem a little low and interaction with a portable player may occur.
Head-Direct and HiFiMAN websites.
Product pages for RE-262 and RE-272.
Head-Fi threads and reviews for the RE-272 here, here, here, and here.
Head-Fi threads and reviews for the RE-262 here and here.