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We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-10-02 · 7 min read · Independent comparison
• Superlux HD 661 — biggest strength: a 40mm dynamic neodymium driver with 68Ω impedance, 102dB sensitivity and a 10Hz–20kHz range, in a sealed over-ear design built for monitoring in loud spaces.
• Superlux HD 661 — biggest trade-off: it is a wired, over-ear headphone with no detachable cable and no microphone, so it stays at the desk rather than in your pocket.
• H HIFIHEAR KZ AS16 — biggest strength: a 16-unit balanced-armature array with a three-channel acoustic duct, 111dB sensitivity, a 20Hz–40kHz range and roughly 26dB of passive noise isolation in a resin shell.
• H HIFIHEAR KZ AS16 — biggest trade-off: at 23.5Ω it is a low-impedance, sensitive in-ear, so it is fussier about fit and about the noise floor of whatever you plug it into.
• Pick the Superlux HD 661 if you want a sealed over-ear monitor for studio, broadcast or live work.
• Pick the H HIFIHEAR KZ AS16 if you want a compact in-ear with a mic, a swappable cable and strong isolation for tracking or on-the-go listening.
The HD 661 is a sealed, over-ear studio monitor headphone. Inside sits a 40mm dynamic driver with a neodymium magnet, rated at 68Ω impedance and 102dB SPL sensitivity at 1kHz, with a frequency band of 10Hz to 20,000Hz. That combination is the whole story of this headphone: 68Ω is a middle-ground load that most headphone outputs, audio interfaces and mixers can drive without strain, while the sealed cup is there to keep outside sound out and your monitoring signal in.
The design intent is clear from the accessories as much as the specs. You get a 3.3 ft cable and a 9.8 ft cable, a gold-plated 3.5mm-to-6.3mm adapter, a cable loss clip and a carrying pouch. A short cable for a laptop or phone, a long one for a desk or a live position, and a quarter-inch adapter for pro gear — that is a monitoring kit, not a commuting kit. The gray neoprene enclosure keeps the weight and finish practical rather than showy, and the volume control on the cable is a small convenience for quick level trims.
This is the headphone I would point a home-recordist at when they track in the same room as a noisy computer, or a podcaster who needs to hear themselves without dragging a boom arm's worth of open-back bleed into the mic. It also suits anyone who simply prefers the feel of a full-size over-ear to anything pushed into their ear canal for a two-hour session.
H HIFIHEAR KZ AS16: Who It's For
The KZ AS16 Pro is a 16-unit balanced-armature in-ear monitor. The driver layout is split by band: four 31736 high-frequency balanced armatures, two 29689 mid-frequency units and two 22955 low-frequency units, with a pair of 22955s dedicated to bass energy output. H HIFIHEAR feeds those through a three-channel acoustic duct structure — a three-way design where each channel's airflow is tuned so the crossover between the armatures stays accurate and consistent, made possible by 3D-printed internal geometry.
The numbers back up the approach. Sensitivity is 111dB, impedance is 23.5Ω, and the frequency response runs from 20Hz to 40kHz. High sensitivity plus low impedance means the AS16 Pro gets loud from almost anything — a phone, a dongle, a laptop jack. The flip side is that a low-impedance, high-sensitivity in-ear will also reveal hiss from a noisy output, so it rewards a clean source.
Where this in-ear earns its place is isolation and fit. The resin shell is shaped from auricle sampling data, and H HIFIHEAR rates the isolation at around 26dB when worn correctly. The ear-hook design keeps the cable routed over the ear and out of the way, which is exactly what you want when you are tracking a vocal or playing for a long stretch. The package includes the earphones, a 2-pin detachable OFC oxygen-free copper cable, three pairs of elastomer eartips in S/M/L, and a user manual, plus a one-year warranty. The 2-pin interface means the cable is replaceable and swappable, and the version here includes a microphone and remote controls. The shell is a cyan resin with metal inlay detailing.
Who should skip it? If you dislike anything inside your ear canal, or you need to hear your surroundings for safety, a sealed in-ear is the wrong choice. And if you want a single, fixed cable you never think about, the detachable 2-pin is a feature you will not use.
• Best for monitoring in a noisy room on a full-size headphone → Superlux HD 661. The sealed over-ear cup and 68Ω load suit studio, broadcast and live positions.
• Best for maximum isolation → H HIFIHEAR KZ AS16. Roughly 26dB of passive isolation from a fitted resin in-ear is a different category of quiet than an over-ear.
• Best for plugging into anything and getting loud → H HIFIHEAR KZ AS16. 111dB sensitivity at 23.5Ω is easy to drive from modest outputs.
• Best for a fixed desk setup with pro connectors → Superlux HD 661. The 3.3 ft and 9.8 ft cables plus the gold-plated 3.5mm-to-6.3mm adapter cover laptop and quarter-inch gear.
• Best for calls and remote controls → H HIFIHEAR KZ AS16. It includes a microphone and media/remote controls; the HD 661 has no mic.
• Best for replaceable cabling → H HIFIHEAR KZ AS16. The 2-pin detachable OFC cable can be swapped; the HD 661's cable is fixed.
• Best for extended wear without anything in your ear canal → Superlux HD 661. A full-size over-ear avoids in-ear pressure over long sessions.
• Best for extended wear with a secure, low-profile fit → H HIFIHEAR KZ AS16. The ear-hook design and sampled cavity are built for long, stable wear.
In my opinion, the deciding question is not which spec sheet is longer — it is where you will actually wear these. If your work happens at a desk, in front of an interface or a mixer, and you want a sealed over-ear you can put on and forget about, I would buy the Superlux HD 661. Its 68Ω load, 40mm dynamic driver and dual-cable kit are aimed squarely at monitoring, and it does that job without asking you to fuss with fit. I would only steer you to the H HIFIHEAR KZ AS16 if isolation, portability, a microphone or a detachable cable matter more to you than the over-ear experience — in which case its 16 balanced armatures, three-way duct and 26dB of isolation are the stronger answer.
FAQ
do high impedance headphones sound better
is high impedance good for headphones
It can be, for the right use case. A higher-impedance headphone tends to be less sensitive to the output impedance of the amp or interface feeding it, which is useful in studio and broadcast setups. It is not inherently better or worse than a low-impedance design — the KZ AS16 at 23.5Ω is simply built for a different job, where high sensitivity and easy drive from portable sources matter more.
are high impedance headphones better
Better for some things, not all. If you are monitoring at a desk from an interface or mixer, a moderate impedance like 68Ω is a sensible, stable match, which is exactly what the HD 661 is designed around. If you are tracking with an in-ear and need isolation and efficiency instead, the low-impedance, 111dB-sensitive KZ AS16 is the better fit. Match the load to the gear, not the other way round.
why are high impedance headphones better
They are not universally better — the advantage is electrical, not magical. A higher impedance makes the headphone less affected by the amplifier's own output impedance, which can keep the frequency response more consistent across different sources, and it draws less current for a given voltage. That is why studio-oriented designs like the HD 661 sit at 68Ω, while portable in-ears like the KZ AS16 go the other way and prioritise sensitivity.
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