This week we’re testing the RHA T20i earphones ? an in-ear model featuring dual coil dynamic drivers in a bass reflex enclosure which comes with several sets of passive filters and a remote control cable for iOS and Android smartphones and tablets. Technically speaking, these earphones are highly advanced as they use technology normally reserved for speakers.
RHA T20i: dual coil drivers
The RHA T20i earphones feature wide-band drivers, which can cover frequencies ranging from 16 Hz to 40 kHz, thus granting them the Hi-Res Audio label. They have an impedance of 16 Ohms for a sensitivity of 90 dB. These values ensure a high sound level with any source, even though 90 dB is a low value, as placing the driver in the ear canal greatly heightens its efficiency.
The special feature of these drivers is that they use not just one driver but two. This technique optimises the performance of the driver over two separate frequency ranges as each coil is connected to a specific passive filter. The low range is thus confined to one coil while the mid-range and treble are reserved for the second.
RHA T20i: bass-reflex port
RHA T20i earphones aren’t closed like most in-ear models but open at the back of each earpiece shell, using a small port. This bass-reflex design improves driver efficiency in low frequencies. Don’t however get confused between the bass-reflex port in these earphones and those found in speakers.
Even though the principle is the same, the bass-reflex port of a speaker operates at a lower frequency due to the greater internal air volume. The small dimensions of an in-ear earphone only permit an impact on the upper-bass range, thus providing a nervy feel to the music or balancing too high a response curve (greater sensitivity in the mid-range and treble). This also applies to the RHA T20i model.
RHA T20i: manufacturing quality
The manufacturing quality is excellent ? well defined steel earpiece shells. The earphones are therefore solid and relatively heavy, which cries out good vibration qualities. The cable features a thick silicone sleeve, which is reinforced with memory form materials for the top part next to the earphone so that users can easily place the cable around their ears. The mini-jack connector is held securely in place using a stainless steel clip, extended via a spring which prevents any excessive twisting of the cable.
RHA T20i: accessories included
A wide range of accessories is supplied with the RHA T20i earphones ? no fewer than ten pairs of ?comply? silicone and foam tips, three pairs of passive filters, cable clips and a carry case.
RHA T20i: test conditions and listening impressions
We listened to the RHA T20i earphones with the HiFiMAN EF2C headphone amp and the Sony PHA-1AEU headphone amp paired up with the Xiaomi Redmi Note 2 smartphone. The initial impression is that putting the earphones in your ears requires a certain amount of skill as you have to place the cable around your ear to ensure that the earphones stay in place. The cable does however pick up some noise interference when moving around but this doesn’t affect the overall listening experience.
The sound is extremely clear with a dynamic sound stage incorporating multiple layers. Transients are clearly good on the audible bandwidth. Upper treble is somewhat subdued, regardless of the chosen filter. The orange filter favours the high end of the sound spectrum and offers a bright but pleasant listening experience. The white filter (systematically installed) softens the high treble to the benefit of the bass range which consequently gains in depth. The black filter softens both treble and medium, again to the benefit of the low range.
Out of the three filters, it was the orange one we liked the most. Listening is clear and more perceptible.
Playing around with the equalizer on our smartphone allowed us to obtain a more suitable balance. The other two filters are less convincing and muffle the listening experience, most likely due to too high an internal damping.
RHA T20i: conclusions
We liked the lively nature of the RHA T20i earphones, despite the over-emphasis of the medium range. This particularity in the frequency response shouldn’t be viewed as a defect but rather the result of the high-quality drivers which don’t suffer from any mechanical coloration. The secret to these earphones is the built-in equalizer integrated to audiophile grade portable players and smartphones, which can be used to soften the range by 2 to 5 kHz.
As most portable players and smartphones feature an integrated equalizer, the response curve can be altered favourably without affecting the overall audio message, thus enabling listeners to benefit from the wide sound stage and dynamic drivers.