A single 14.8 mm planar IEM (plus a passive pressure-relief module) that trades the S12's bright, aggressive planar character for a smooth, full-bodied one. Reviewers broadly agree on a big, clean, well-controlled bass that 23 measurement rigs place as a +6–8 dB shelf leaning slightly toward the mid-bass; long-session comfort with no pressure build-up; a light shell with a genuinely good modular cable (2.5 / 3.5 / 4.4 mm); a stage that is wide but not deep; good separation; and ordinary-to-good isolation. They split on how to describe it — warm and relaxed for most, neutral to mildly bright for a large minority — and the measurements explain why: the ear-gain peaks early near 2 kHz, then sits 5–7 dB under the Harman target from 3 to 6 kHz before a narrow lift around 7–8 kHz. That shape makes the midrange sweet and forward to three quarters of sources and stuffy to the rest, and splits the treble three ways: smooth and fatigue-free, under-energised with little air, or occasionally sibilant on a shallow fit. Detail, dynamics and value are contested too. Value is the closest split, and most of the criticism was written against the $329 launch price; the set now sells for $179 new.
About this product
The late-2023 planar above the S08 and S12 Pro: a third-generation 14.8 mm planar driver paired with a 6 mm 'R-Sonic' passive filtering module, in a light 3D-printed resin shell with an anodized aluminium faceplate. Despite the name it is not a refresh of the S12 — it shares neither the metal housing nor the tuning, and reviewers routinely warn S12 owners not to read it as an upgrade path. There is no 'S15 Pro' (one Head-Fi review is titled that way, but no such product exists), and the R-Sonic module works as a pressure-relief vent, not the passive radiator early marketing implied. Letshuoer's own store also sells an open-box unit and, earlier, a bundle with its DT03 dongle.
The Letshuoer S15 arrived in late 2023 with an awkward job: succeed the S12, one of the most-recommended budget planars ever made, at roughly three times its price. Letshuoer's answer was not a louder S12 but almost its opposite — a third-generation 14.8 mm planar in a feather-light 3D-printed shell, tuned warm and smooth instead of bright and raw, with a 6 mm 'R-Sonic' module venting pressure out of the cavity so the set stays comfortable at volume.
Two years on, the argument has a clearer shape. Almost everyone agrees on the bass, the comfort, the cable and the box. What still divides people is the region where a voice gets its edge: the S15's ear-gain peaks early, around 2 kHz, and then falls well below the usual target — which reads as sweet and intimate to most listeners and as stuffy or under-lit to a vocal minority. The price has moved even more than the opinions: the $329 that drew the sharpest reviews is now $179 at Letshuoer's own store.
