After my deep investigation into the Questyle M12i, I was curious about what its bigger sibling, the M15i, could bring to the table. It’s small enough to disappear in your pocket, yet from the first listen it became clear—this isn’t just a step up, it’s a different league. Using the HiBy R4 as my source and the Letshuoer S12 as my reference IEM, I set out to explore every corner of its sound.
Design & Tech
The M15i carries Questyle’s signature look—a CNC-machined anodized aluminum body topped with a transparent glass panel that shows off the internals. Inside, the ES9281AC flagship DAC and dual independent CMA SiP amp modules handle the conversion and amplification duties. It supports up to 32-bit/768kHz PCM and native DSD512, offers both 3.5mm SE and 4.4mm balanced outputs, and features two gain levels. The build is minimalist yet premium, and the detachable USB-C cable means easy replacement if needed.
Specifications:
– 3.5mm Output: RL = 300Ω, Po = 11.97mW, Vout (Max) = 1.895Vrms, THD+N = 0.0003%
– 4.4mm Output: RL = 300Ω, Po = 22.60mW, Vout (Max) = 2.624Vrms, THD+N = 0.0003%
– Frequency Response: ±0.1dB (20Hz-20kHz); ±2dB (20Hz – 80kHz)
– THD+N: 0.0003%
– DAC: ESS Flagship USB DAC Chip ES9281AC
– Exterior Material: CNC Anodized Aluminum Alloy
– Color: Black
– Dimensions: 61.9 [L] x 27.9 [W] x 12 [D] mm
Sound Analysis
Bass
On first listen, the bass is not about brute force—it’s about authority. With Asian Dub Foundation – Fortress Europe, sub-bass drops dig deep but remain tightly controlled, never bleeding into the mids. Even on the Letshuoer S12, which is not known for heavy low-end, the M15i adds a sense of body and grip.
Switching to Marcus Miller – Panther, the mid-bass punch is textured and precise. You can follow the fingers sliding across the strings, with every pluck delivering a tactile impact. It’s not exaggerated; it’s disciplined.
In electronic tracks like Knife Party – Centipede, kick drums hit with speed and decay naturally, letting the rest of the mix breathe. This makes the M15i a great match for both bass-driven genres and acoustic recordings.
Midrange
The midrange is where the M15i’s musicality really shines. Listening to Queen – Love of My Life (Live at Wembley), Freddie Mercury’s voice sits perfectly centered, full-bodied without being overly warm. Guitars have the right amount of bite without harshness.
On TSM (Turkish Sufi Music) recordings, instruments like oud and qanun gain depth and natural resonance, each note decaying into a black background. It’s intimate yet spacious.
In Brazzaville – Green Eyed Taxi, the saxophone floats in front of me while vocals are layered behind, creating a scene that feels almost tangible. The M15i never lets the mids get veiled, even in busy arrangements.
Treble
Treble performance is refined and extended without any sharp edges. In The Cure – Pictures of You, the shimmering guitar layers come through with clarity, and the cymbal hits are airy yet smooth.
With Miles Davis – So What, trumpet notes extend naturally, and the gentle ride cymbal keeps its shimmer without becoming fatiguing over longer sessions.
In orchestral pieces, violins have both sweetness and precision, avoiding the metallic glare some dongles can produce. High-gain mode adds a bit more sparkle and openness, but even on low gain, the treble is articulate and natural.
Genre Performance
- TSM: Layered, resonant, each instrument stands in its own space.
- Asian Dub Foundation: Absolute control in the low end, silent background.
- Blues: Physical presence in vocals and drums, emotional connection intact.
- Brazzaville: Concert-like staging with relaxed flow.
- The Cure: Atmospheric, immersive, with wide dynamic swings.
M12i vs M15i vs M18i COMPARISONS
| Model | Strengths | Target User |
| M12i | Clean, lean, budget-friendly | Entry-level IEM users |
| M15i | Balanced, spacious, musical | Those wanting portable “reference” sound |
| M18i | Ultimate control, high resolution | Demanding listeners / desktop replacement |
Pros & Cons
Pros:
- Balanced, natural tonal signature
- Wide, deep, and tall soundstage
- Excellent detail retrieval without fatigue
- Strong output power, dual gain
- Premium build and transparent design
Cons:
– Needs quality IEMs to shine
– Slight warmth on high gain with sensitive IEMs
– Cable connector could loosen over time
Conclusion Of Questyle M15i Review
The Questyle M15i is more than just the middle child between the M12i and M18i—it’s a sweet spot. It captures the M18i’s authority and technicality, but tempers it with a warmth and musicality that makes long listening sessions effortless. It’s compact enough for everyday carry, yet powerful enough to challenge mid-tier DAPs.
If you’re looking for a portable DAC/amp that delivers reference-level performance with soul, the M15i is one of the strongest contenders out there. For me, it turned the S12—a well-respected planar IEM—into something I could confidently take to a critical listening session or just enjoy casually at home. That’s a rare balance to strike, and the M15i hits it at 12!