We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-10-06 · 6 min read · Independent comparison
If you want a compact dual balanced-armature in-ear tuned for vocal presence and isolation, choose Astell&Kern Billie Jean in-Ear; if you need a planar-magnetic reference monitor with a wider soundstage and flexible 3.5/4.4 mm connectivity, choose Hidizs MP145. Both are wired in-ear monitors aimed at the same buyer — the audiophile who cares more about detail and tuning than about wireless convenience — but they get there in completely different ways. One is a tiny, isolating two-driver design; the other is a larger planar monitor built for studio-style clarity.
• Astell&Kern Billie Jean in-Ear — biggest strength: dual balanced-armature drivers in a small silicone shell with sound isolation, so vocals and presence come through cleanly and outside noise stays out.
• Astell&Kern Billie Jean in-Ear — biggest trade-off: a 3.5 mm wired connection only, and a modest accessory set (one cable, three silicone tip sizes, a case) — no balanced plug option.
• Hidizs MP145 — biggest strength: a 14.5 mm planar-magnetic driver with a 20 Hz–40 kHz range, plus your choice of 3.5 mm or 4.4 mm plugs for reference-grade, wide-soundstage listening.
• Hidizs MP145 — biggest trade-off: planar IEMs are physically larger and demand more from your source to sound their best; the earpieces are heavier than a tiny armature design.
• Who the Billie Jean is for: listeners who want an isolating, easy-to-drive everyday IEM for vocals and portable players.
• Who the MP145 is for: listeners chasing reference-monitor accuracy, deep sub-bass control and a holographic stage who own (or plan to own) a balanced-output source.
The Billie Jean is a Jerry Harvey Audio design built around two balanced-armature drivers. Balanced armatures are the classic choice for in-ear monitors because they're tiny and efficient, and that's exactly what you get here: a small blue shell that sits deep in the ear. The silicone enclosure keeps the weight down, and the stated sound-isolation design means the fit itself does a lot of the work of blocking the room around you.
Who should buy it: someone who wants a genuinely isolating, low-hassle IEM for a portable player or phone with a 3.5 mm jack, and who values presence over sheer low-end weight. Who should skip it: anyone who wants a balanced 4.4 mm connection, a replaceable cable ecosystem, or the bigger, more spacious presentation that planar drivers are known for. The kit is deliberately minimal — 3.5 mm cable, silicone tips in S/M/L, and a carrying case — so if you like to tinker with cables and plugs, this isn't the pick.
Hidizs MP145: Who It's For
The MP145 Pro is a planar-magnetic in-ear monitor, and that driver type is the headline. A 14.5 mm ultra-precision planar diaphragm with higher copper content is claimed to deliver faster transient response, paired with upgraded N54H magnetic arrays for stronger flux density. Translated out of spec-speak: planars are prized for speed and control, and Hidizs is explicitly aiming at "studio-track clarity" and reference immersion — the exact language of a reference monitor.
The tuning described is textbook reference: surgical bass control with real sub-bass extension but no mud, a transparent midrange that doesn't color vocals or instruments, upper mids that carve out pinpoint imaging, and treble that extends with airiness. The 20 Hz–40 kHz frequency range backs up that ambition on paper. If you record, mix, or simply want to hear a track the way it was assembled, this is the profile you're shopping for.
Comfort and connection are where it differentiates further. Each earpiece is listed at just 9.5 g despite magnesium alloy reinforcement, and the acoustic tubes were redesigned to reduce fatigue over long sessions — relevant, because reference listening tends to be long listening. You get both 3.5 mm and 4.4 mm plug options, a 4-core 6N OFC cable with silver plating, liquid silicone eartips, and a leather case. Who should skip it: buyers who want the smallest possible shell, or who only ever use a plain 3.5 mm output and won't use the balanced option at all.
• Best for vocal presence and brilliance → Astell&Kern Billie Jean in-Ear. The bore design is tuned for presence, and dual armatures keep the midrange forward.
• Best for reference-monitor accuracy → Hidizs MP145. Planar driver, controlled bass, uncolored mids and a 20 Hz–40 kHz range.
• Best for sound isolation → Astell&Kern Billie Jean in-Ear. Sound isolation is a stated design feature of the shell and fit.
• Best for wide, holographic soundstage → Hidizs MP145. Planar drivers are the reason it can push stage width the way it claims.
• Best for balanced-output gear → Hidizs MP145. It ships with 3.5 mm and 4.4 mm options; the Billie Jean is 3.5 mm only.
• Best for long mixing or editing sessions → Hidizs MP145. 9.5 g per side and redesigned acoustic tubes aimed at reducing fatigue.
• Best for a minimal, grab-and-go kit → Astell&Kern Billie Jean in-Ear. Small shell, single cable, three tip sizes, case.
• Best for cable and tip tinkering → Hidizs MP145. Upgraded OFC cable plus liquid silicone eartips included.
In my opinion, I'd buy the Hidizs MP145. For an audiophile in 2026, the planar driver, the reference-style tuning and the dual 3.5/4.4 mm connectivity give it more room to grow with your source, and the 20 Hz–40 kHz range plus the comfort engineering make it the more versatile long-session monitor. The Billie Jean is the better call only if isolation, a tiny shell and vocal-forward presence matter more to you than stage width and balanced output. Either way, check the current price on Amazon before you commit, since the value math shifts with whatever each one is going for when you buy.
FAQ
what is studio monitor headphones
Studio monitor headphones are designed to reproduce audio as neutrally as possible so you hear the recording rather than a colored version of it. That's the design goal Hidizs states for the MP145 — transparent mids, controlled bass and extended treble.
Reference studio headphones are the same idea: a flat, uncolored response used as a benchmark for judging a mix. The MP145's described tuning — surgical bass control, natural vocal textures, airy treble — is squarely in that reference camp.
what are studio monitor headphones
They're headphones or in-ear monitors built for accuracy over excitement, so detail and imaging take priority over boosted bass. The Billie Jean leans the other way, using its bore design for presence and brilliance rather than strict neutrality.
can you connect headphones to monitor
Yes — studio monitors and headphones are separate links in the same chain, and you can run headphones from a monitor controller, audio interface or headphone amp. The Billie Jean uses a 3.5 mm wired jack, while the MP145 supports both 3.5 mm and 4.4 mm, so it fits more output types.
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