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We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-09-23 · 6 min read · Independent comparison
If you want a closed-back, over-ear studio monitor you can wear for long editing or tracking sessions, choose Superlux HD661; if you need a compact in-ear with a planar driver and a genuinely wide frequency range for critical listening on the move, choose Linsoul 7HZ.
• Superlux HD661's biggest trade-off: it's a wired, bulky over-ear with a Bluetooth mention in the spec sheet that doesn't match its wired 3.5mm jack — treat it as a cable-first studio tool, not a wireless headset.
• Linsoul 7HZ's biggest strength: a 14.2mm planar magnetic driver with a listed 5Hz–40,000Hz range, 104dB sensitivity and a detachable MMCX cable in a shell that weighs about 5g per earbud.
• Linsoul 7HZ's biggest trade-off: it's an in-ear monitor, so isolation depends on fit and tips, and it has no over-ear cup to block a noisy room the way a closed-back can.
• Pick the Superlux HD661 if you want a full-size closed monitor for studio, broadcast or noisy-room work.
• Pick the Linsoul 7HZ if you want a lightweight, upgradeable in-ear for instrumental listening and portable use.
The HD661 is a closed-back, over-ear monitor built around a single 40mm dynamic driver with a neodymium magnet. Superlux rates it at 102dB SPL (1mW) at 1kHz and 68Ω impedance. That impedance number is the one to pay attention to: 68Ω is higher than typical earbuds and phone-friendly cans, so it wants a bit more voltage to reach the same loudness. A phone will drive it, but a dedicated amp or an audio interface headphone out will let it breathe. In my opinion, that's a studio-first spec, not a commuter spec.
The listed frequency band is 10Hz–20,000Hz, and the housing is sealed. That airtight enclosure is the whole point of this headphone: the design brief is live monitoring, studio use and broadcast, where you need the deep sound field to stay put and external noise to stay out. The over-ear pads are neoprene, which is a practical, sweat-tolerant material for long sessions, and the whole thing weighs 6.72 ounces — noticeable on your head, but normal for this class.
Buy it if you record, monitor, edit, stream or work in a room that isn't quiet and you want a wired, closed, over-ear tool with a balanced tone and enough resolution to trust what you're hearing. Skip it if you want something pocketable, wireless-first or featherweight — the HD661 is none of those. It ships with a 3.3ft cable and a 9.8ft cable, a 3.5mm-to-6.3mm gold-plated adapter, a cable clip and a carrying pouch, which tells you Superlux expects you to plug into real gear, not just a phone.
The 7HZ Timeless is an in-ear monitor with a 14.2mm planar magnetic driver. Planar drivers move a thin diaphragm across a large, flat surface rather than pushing a cone, and 7HZ pairs this with a double-sided array of N52 magnets and an ultra-thin diaphragm. The result, per the spec sheet, is a fast response, wide dynamic range and a listed frequency range of 5Hz–40,000Hz at 104dB sensitivity. That's a genuinely wide figure, and it's the reason this earphone gets talked about in flat-response and neutral-tuning conversations.
The shell is CNC-milled from a single piece of aviation-grade aluminum with hard oxidation treatment, so it's built to take a beating. Each earbud weighs about 5g, and the shape is a rounded-tip in-ear, which matters because fit is what determines both comfort and isolation here. The cable is detachable via MMCX, made with single-crystal copper and silver-plated single-crystal copper inner cores under a silver foil outer layer — and because it detaches, you can swap or upgrade it later. That's a real long-term ownership advantage over a fixed-cable design.
Buy it if you want a neutral-leaning, transparent in-ear for instrumental music, critical listening or quiet focused work, and you value a replaceable cable and a metal shell. Skip it if you need maximum passive blocking in a loud room, if you dislike in-ear fit, or if you want a full-size over-ear presentation. There's a 1-year warranty listed, and the package includes a cable and a carrying case.
Side-by-Side: Which Should You Choose?
• Best for flat, neutral-leaning tuning → Linsoul 7HZ. The planar driver, wide listed range and transparent tuning description point straight at accuracy-first listening.
• Best for long sessions on your head → Linsoul 7HZ. At roughly 5g per earbud it disappears; the HD661 is 6.72 ounces.
• Best for studio, broadcast and live monitoring → Superlux HD661. That's literally what its design and accessory set are aimed at.
• Best for portable, pocketable use → Linsoul 7HZ. Smaller, lighter, and its cable detaches for storage or replacement.
• Best for upgradeability → Linsoul 7HZ. The MMCX connector means the cable is a replaceable part, not a fixed one.
• Best for plugging into an interface or amp → Superlux HD661. 68Ω impedance rewards a proper headphone output.
• Best for phone-and-dongle listening → Linsoul 7HZ. 104dB sensitivity means it gets loud easily from modest sources.
If I were buying for a desk, a studio or a noisy room, I'd take the Superlux HD661 — the closed-back over-ear design, the 68Ω/40mm driver and the two-cable accessory kit make it the more capable monitoring tool, and I'd just feed it from a real headphone output. If I were buying for listening on the move, for instrumental music or for a neutral in-ear I can keep upgrading over time, I'd take the Linsoul 7HZ. It's lighter, more sensitive, and the detachable MMCX cable makes it the smarter long-term buy in my opinion. Two different jobs, two different answers — pick the one that matches how you actually listen, then check the current price on Amazon before you commit.
Yes, it matters — but the numbers alone don't tell the whole story. The HD661 lists 10Hz–20,000Hz and the 7HZ lists 5Hz–40,000Hz, which tells you the 7HZ is specified to cover more range at both ends; how that range is balanced is what you actually hear. A wide figure is a capability statement, not a guarantee of a flat sound.
Not automatically better — different. Planar drivers like the 14.2mm unit in the 7HZ tend to be described as fast and low-distortion, which suits neutral tuning. The 40mm dynamic driver in the HD661 is a proven, simple design that Superlux tunes for balanced monitoring. Both can be accurate; they get there differently.
It depends on the job. Over-ear closed-backs like the HD661 are the traditional choice for tracking, broadcast and noisy rooms because they cover the ear. In-ears like the 7HZ are common for stage and portable monitoring where you want minimal bulk and maximum isolation from a good seal.
Both are built for real use, in different ways. The 7HZ uses a CNC-milled aviation-grade aluminum shell with hard oxidation treatment and a detachable cable, so the cable is replaceable. The HD661 is a plastic-and-neoprene over-ear with fixed cables and a hard-wearing over-ear frame. In my opinion the 7HZ's replaceable cable gives it the edge for long-term ownership.
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