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We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-10-05 · 7 min read · Independent comparison
• Fostex TH-610 — biggest strength: a 50mm dynamic driver with a 1 tesla magnetic circuit and a Bio-dyna diaphragm, tuned for rich lows and smooth highs across a 5Hz–45kHz range.
• Fostex TH-610 — biggest trade-off: it is a wired, over-ear, non-noise-cancelling headphone with no isolation mentioned and no battery, so it is a stay-put listening tool, not a commuter gadget.
• syeindunce Celest PhoenixCall 2.0 — biggest strength: a six-driver hybrid setup (2DD + 2BA + 2 planar) with a switchable 3.5mm/4.4mm plug, so it adapts to phones, DAC/AMPs and digital audio players.
• syeindunce Celest PhoenixCall 2.0 — biggest trade-off: in-ear sound isolation is great for focus but it is a very different physical experience, and at 11 ohm impedance it is a low-impedance load that behaves differently with different sources.
• Pick the Fostex if you want one wooden pair of headband headphones for library sessions where you want to hear a little of the room around you.
• Pick the Celest if you want an open ear earbuds–style alternative, with microphone open ear earbuds convenience in a wired audiophile package.
The TH-610 is the classic Fostex formula: black walnut housings with a matte finish, a detachable cable with a 2-pin connector that is compatible with the TH900mk2, and a 50mm dynamic driver built around a 1 tesla (1,000 gauss) magnetic circuit. Fostex claims that circuit gives wide dynamic range with low distortion, and the Bio-dyna diaphragm is tuned for rich lows, natural mids and smooth highs. The stated frequency range runs from 5Hz to 45kHz and sensitivity is 98dB/mW, which tells you this is a headphone that wants a decent source rather than a phone dongle afterthought.
For library use specifically, this is a headband headphones design with low-repulsion artificial leather ear pads, which matters more than people expect when you are sitting still for two or three hours. Low-repulsion cushioning spreads pressure instead of pinching, so the clamp stays tolerable past the point where cheaper pads start to ache. The wood enclosure is also doing work acoustically and visually — it is a warm, furniture-grade object that looks at home on a desk rather than a gym bag.
Who should skip it? Anyone who needs to block out a loud room. Noise control is listed as none, and nothing in the sheet suggests the cups seal tightly enough to erase a noisy HVAC vent or nearby conversation. If you want active isolation, look elsewhere. Also skip it if you want a mic for calls — there is a media control remote on the cable, but no microphone feature is listed, so do not buy it as a headset for meetings.
The PhoenixCall 2.0 is the opposite philosophy in a much smaller package. It is a six-driver hybrid IEM: dual dynamic drivers for the low end, dual balanced armatures, and dual planar drivers, which together are claimed to deliver deep bass, natural mids and extended treble with better layering and clarity. That is a lot of driver types packed into a resin in-ear shell, and the point of a hybrid like this is that each driver family handles the band it is good at instead of forcing one driver to do everything.
The genuinely useful feature for a student or library regular is the switchable cable. It supports both a 3.5mm single-ended connection and a 4.4mm balanced plug, so you can move between a phone, a dongle DAC, a portable player or a desktop amp without buying a second cable. For anyone chasing a hi res headset setup in a library, that flexibility is the whole game — the same earphones can serve a laptop and a dedicated player.
Fit is the other headline. The ergonomic in-ear design is meant for long listening sessions, and sound isolation is listed as the noise control method. That cuts both ways: it is excellent for focusing in a shared space, but it also means you should expect to hear less of the world around you. They ship with a protective case, spare ear cushions and eartips, and the color options include Red-Gold, Blue-Silver, Black-Gold and Dusk-Gold. Impedance is 11 ohm and sensitivity is 108dB, so they are easy to drive — arguably too easy with noisy sources, since low-impedance, high-sensitivity IEMs can reveal hiss from a cheap output.
Skip these if you dislike having something inside your ear canal for hours, or if you want the open, airy presentation a big wooden cup gives you. Skip them too if you want one cable and one device forever — the switchable plug is only a benefit if you actually use it.
Side-by-Side: Which Should You Choose?
• Best for library focus and blocking out chatter → syeindunce Celest PhoenixCall 2.0, because sound isolation is part of the design.
• Best for device flexibility → syeindunce Celest PhoenixCall 2.0, with its 3.5mm and 4.4mm switchable plug.
• Best for a warm, natural tonal signature from a full-size driver → Fostex TH-610, with its 50mm Bio-dyna driver and 1 tesla circuit.
• Best for detailed layering and driver separation → syeindunce Celest PhoenixCall 2.0, given the 2DD + 2BA + 2 planar architecture.
• Best for portability → syeindunce Celest PhoenixCall 2.0, which packs into a protective case instead of sitting on your head.
• Best for a wide frequency range spec → Fostex TH-610, quoted at 5Hz–45kHz versus the Celest's 20kHz ceiling.
• Best if you hate things in your ear canal → Fostex TH-610, no contest.
For a library, I would buy the Fostex TH-610. The reason is simple: a library is a place where you sit still for a long time, and the TH-610 is built for exactly that — over-ear cups, low-repulsion pads, a 50mm driver with a 1 tesla circuit and a detachable cable you can replace if it wears out. In my opinion, that combination suits a hi res headset for library listening better than any in-ear, because it never asks you to jam a tip into your ear canal for three hours straight.
I would only switch to the syeindunce Celest PhoenixCall 2.0 if the room is genuinely loud, if I need to move between devices with 3.5mm and 4.4mm outputs, or if I want something that lives in a pocket. Both are wired, both are serious about sound, and they are aimed at different people. Check the current price on Amazon for each before you commit.
FAQ
It depends on the room. The Celest isolates you from noise, which helps in a busy library. The Fostex is more comfortable for long, still sessions and lets a little room sound through, which many people prefer for hours of reading.
No. They come with a switchable plug for both 3.5mm and 4.4mm, so they work with phones, DAC/AMPs and digital audio players. At 11 ohm and 108dB they are easy to drive, so a dedicated amp is optional rather than required.
The sheet lists a media control remote on the cable but no microphone, so treat it as a listening headphone first. If you need voice chat, you would need a separate mic solution.
The Celest ships with a protective case and resin shells, which suits tossing in a bag. The Fostex is a wooden over-ear with a detachable cable, so it is better kept on a desk or stand than crushed in a backpack.
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