How We Research
We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
If you want reference-grade, wired audiophile sound with deep sub-bass and an open, breathable design for long listening sessions, choose Sennheiser HD 660S2; if you need an open-ear wireless headset with a boom microphone, environmental noise cancellation and all-day battery for calls and communication, choose OPN Sound Chat Pro. These two headphones solve completely different problems — one is built for music, the other for talking.
• Sennheiser HD 660S2 biggest strength: 42mm high-performance transducers with a vented magnet system, 300-ohm impedance and a frequency range of 8 Hz – 41,500 Hz for detailed, high-fidelity music listening.
• Sennheiser HD 660S2 biggest trade-off: It's a wired, open-back headphone with no microphone, no battery and no wireless connectivity — you need a suitable source and a quiet room.
• OPN Sound Chat Pro biggest strength: An open-ear wireless design with a directional audio driver, ENC boom microphone and 17-hour battery life, made for calls and staying aware of your surroundings.
• OPN Sound Chat Pro biggest trade-off: It's a communication headset, not an audiophile listening tool — no wired jack, no high-fidelity spec sheet, and its focus is voice clarity rather than music reproduction.
• Choose Sennheiser HD 660S2 if you want to sit down and properly listen to music.
• Choose OPN Sound Chat Pro if you want to talk, take calls and stay present in your environment while wearing a headset.
The HD 660S2 is a wired, open-back, over-ear headphone built around a 42mm dynamic driver. Sennheiser's engineering story here is all about airflow: a vented magnet system improves ventilation, and steel mesh damping controls air displacement to keep distortion low. The result, per the specs, is a natural, relaxed tuning with extra sub-bass — Sennheiser claims double the sound pressure at the lowest octaves compared to its predecessor, which is why the spec sheet name-checks the lowest note on a piano (27.5 Hz) and the kick of a bass drum (45–60 Hz).
Comfort is where the open-back design earns its keep. The open enclosure breathes, and the plush ear cushions are meant for extended sessions without fatigue. At 260 grams it's light enough to disappear on your head over a long evening. The aluminum enclosure and included protective case suggest a product built to last. In the box you get a 4.4mm cable (1.8m), a 6.3mm cable (1.8m), and a 6.3mm-to-3.5mm adapter — so desktop use with a proper amp or interface is clearly the intended scenario.
Buy the HD 660S2 if you're a music lover who wants a dedicated, non-fatiguing listening headphone for critical or long-session listening at a desk. Skip it if you need wireless freedom, a microphone, or a headset for calls — it simply isn't that product.
OPN Sound Chat Pro: Who It's For
The OPN Sound Chat Pro is a different animal entirely. It's a wireless, open-ear communication headset with a directional audio driver — OPN Sound positions it as an air-conduction design that delivers rich stereo sound without the vibration you'd associate with bone-conduction headphones. That distinction matters: the marketing describes the speaker type as bone conduction directional audio, but the brand's own framing emphasizes a vibration-free listening experience.
The core use case is communication. The ENC boom microphone uses environmental noise cancellation to isolate your voice from background noise, which is the feature you actually care about on a call. The Direct Connect Dongle is there to keep the wireless link stable and uninterrupted — a practical detail for anyone who's dealt with Bluetooth dropouts mid-meeting.
Battery life is the headline spec: 17 hours of average life, and OPN Sound notes the charge time as 17 hours as well, with fast-charging support. That's a full workday of talking, plus change. The open-ear fit is the other defining trait — nothing goes inside your ear canal, so you stay aware of traffic, coworkers, or a doorbell while you're on a call.
There's no wired jack, no impedance figure, no frequency response published, and no audiophile driver spec. That's not a flaw — it's a signal. This headset is engineered for voice and situational awareness, and it comes with a lifetime manufacturer's warranty, which tells you OPN Sound expects it to be worn daily. The color is black, and it ships with a cable in the box.
Buy the Chat Pro if you spend your day on calls, need to hear your surroundings, and want a headset that lasts a full shift. Skip it if your priority is faithful music reproduction or wired listening.
• Best for music fidelity → Sennheiser HD 660S2. The 42mm transducer, 300-ohm impedance and 8 Hz – 41,500 Hz range are built for critical listening.
• Best for calls and voice clarity → OPN Sound Chat Pro. The ENC boom microphone is designed specifically to keep your voice clear.
• Best for long listening comfort → Sennheiser HD 660S2. Open-back breathability plus plush cushions and a 260g weight for extended sessions.
• Best for all-day use away from a desk → OPN Sound Chat Pro. 17-hour battery life with fast charging means it keeps going through a full day.
• Best for situational awareness → OPN Sound Chat Pro. The open-ear design keeps you tuned into your surroundings.
• Best for staying wired to a desktop rig → Sennheiser HD 660S2. Detachable 4.4mm and 6.3mm cables plus a 6.3mm-to-3.5mm adapter.
• Best for a stable wireless connection → OPN Sound Chat Pro. The Direct Connect Dongle is made to avoid dropouts.
• Best for long-term durability confidence → OPN Sound Chat Pro. It carries a lifetime manufacturer's warranty.
In my opinion, these aren't really competitors — they're answers to two different questions, and I'd buy based on the question you're actually asking. If you want to sit down and listen to music properly, I'd buy the Sennheiser HD 660S2 without hesitation; its driver design and full-range tuning are clearly aimed at serious listening. If you live on calls and need to stay aware of what's happening around you, I'd buy the OPN Sound Chat Pro — the ENC boom mic, open-ear fit and 17-hour battery are exactly what that job needs. Don't buy either one hoping it does the other's job.
For music, the Sennheiser HD 660S2 is the clear choice. It has a 42mm high-performance transducer, a 300-ohm voice coil and a frequency range of 8 Hz – 41,500 Hz. The OPN Sound Chat Pro is designed as a communication headset with no published audiophile driver specifications.
Yes — it's a wireless headset with an ENC boom microphone and a Direct Connect Dongle for a stable connection, which suits voice chat, meetings and calls. It has no headphone jack, so all connections are wireless.
No. The HD 660S2 is a wired, open-back headphone with detachable 4.4mm and 6.3mm cables and no wireless connectivity or built-in microphone. If you need a mic or wireless use, look at the OPN Sound Chat Pro instead.
OPN Sound lists 17 hours of average battery life and a 17-hour charge time, with fast-charging support. That's designed to cover a full day of calls before you need to plug in.
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