We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-09-19 · 7 min read · Independent comparison
If you want the most natural, fatigue-free audiophile sound for long wired listening sessions, choose Amazon Renewed Sennheiser HD 660S2; if you need wireless freedom, active noise cancelling and marathon battery life for commuting and travel, choose Accentum Sennheiser.
• Amazon Renewed Sennheiser HD 660S2 — biggest strength: an open-back, 300-ohm wired design with a 42mm transducer, vented magnet system and 8 Hz–41,500 Hz frequency response built for detail, timbre and deep sub-bass extension.
• Amazon Renewed Sennheiser HD 660S2 — biggest trade-off: it's wired only, open-back (so it leaks sound both ways), needs a capable amp to shine, and as a Renewed unit it carries a 90-day limited warranty rather than a full new-product one.
• Accentum Sennheiser — biggest strength: Bluetooth 5.2 with aptX Adaptive, hybrid noise cancelling and up to 50 hours of playback per charge in a light 226.7 g frame.
• Accentum Sennheiser — biggest trade-off: it's a wireless on-ear with a narrower stated frequency range, so it trades the HD 660S2's openness and resolution for convenience.
• Who the HD 660S2 is for: the listener who sits at a desk or in a quiet room and wants to hear the recording, not the room.
• Who the Accentum is for: the listener who moves — trains, planes, offices and open-plan chaos — and wants one pair to do it all.
The HD 660S2 is the enthusiast's headphone. Everything about its design points one direction: accuracy. The 300-ohm voice coil is ultra-light aluminium, which is exactly the kind of build that produces a clean impulse response — meaning drums hit and decay the way they should, and vocals keep their texture instead of smearing. The 42mm transducer sits in a vented magnet system with steel mesh damping, which the spec sheet credits with minimising distortion and controlling airflow. In plain terms: less grit, more air, more separation between instruments.
Then there's the low end. Sennheiser states the design doubles sound pressure at the lowest octaves, so a piano's bottom note or a kick drum's thump arrives with real weight. The stated frequency response runs from 8 Hz to 41,500 Hz — far beyond what you can hear, but a useful signal that the tuning is deliberately extended rather than rolled off. Meanwhile the open-back enclosure keeps your ears cool and the soundstage wide, and the velour pads are described as plush for a reason: these are headphones you wear for hours, not minutes. The treble is tuned to be detailed but non-fatiguing, which matters if you listen all day.
Accentum Sennheiser: Who It's For
The Accentum is the opposite philosophy executed well: take the music with you. Bluetooth 5.2 with aptX Adaptive handles the wireless link, and the stated range of up to 30 metres means you can leave your phone on the counter and wander. Hybrid noise cancellation is the headline feature for anyone who's ever tried to focus on a podcast in a noisy café — it actively reduces environmental noise so you hear more of what you're playing and less of everything else. The push-button media controls are simple and glove-friendly, and a 40 ms latency figure keeps audio reasonably tight with video.
Battery is where the Accentum genuinely stands apart. Up to 50 hours of playback on a single charge, with a full charge taking about 3 hours over USB-C. That's a week of commuting on one plug-in, or a long-haul trip without hunting for an outlet. At 226.7 g it's light enough to wear through a workday, and the build mixes aluminium, polycarbonate and thermoplastic elastomer — a practical, durable combination rather than a precious one. The 37mm dynamic drivers and 24-ohm impedance make it easy to drive from any phone. Sennheiser also positions the sound as clear, professional-grade for calls, and the box includes a carry bag, USB-C cable and manual.
Who should buy it: commuters, travellers, students, remote workers in shared spaces, and anyone who wants one headphone for music, calls and noise blocking. Who should skip it: the listener chasing maximum resolution, openness and sub-bass depth. Its stated frequency range is narrower, it's an on-ear rather than an open-back over-ear, and no wireless design can match a wired, amp-driven 300-ohm headphone for sheer detail. If critical listening is the goal, this isn't the tool.
Side-by-Side: Which Should You Choose?
• Best for sound quality and detail → Amazon Renewed Sennheiser HD 660S2. The 300-ohm coil, 42mm vented transducer and 8 Hz–41,500 Hz range are built for resolution.
• Best for battery life → Accentum Sennheiser. Up to 50 hours per charge, roughly 3 hours to refill.
• Best for noise cancelling and focus → Accentum Sennheiser. Hybrid ANC is a feature the HD 660S2 simply doesn't have.
• Best for commuting, travel and calls → Accentum Sennheiser. Bluetooth 5.2, aptX Adaptive, 30 m range and clear voice pick-up.
• Best for long desk sessions → Amazon Renewed Sennheiser HD 660S2. Open-back breathability, velour pads and two 1.8 m cables.
• Best for plug-and-play simplicity → Accentum Sennheiser. No amp, no cable, no fuss.
• Best for peace of mind → Accentum Sennheiser, on warranty grounds: new retail versus a 90-day limited warranty on the Renewed HD 660S2.
In my opinion, these two aren't really competitors — they're answers to different questions, and I'd buy based on where you actually listen. If most of your listening happens at a desk in relative quiet, I'd choose the Amazon Renewed Sennheiser HD 660S2: the open-back design, 300-ohm coil and extended sub-bass make it the more rewarding headphone for the money when sound is the point. If you listen on the move, I'd choose the Accentum Sennheiser — 50 hours of battery, hybrid ANC and Bluetooth 5.2 solve problems the HD 660S2 doesn't even attempt. My honest pick for most people reading this? The Accentum, because most of us don't have a quiet room and an amp. But if you do, the HD 660S2 is the one that will move you.
That depends on how you weigh warranty against cost. A Renewed unit carries a 90-day limited warranty instead of a full new-product warranty, so check the current price on Amazon and decide whether the saving justifies the shorter coverage. The hardware itself — 300-ohm coil, 42mm transducer, open-back design — is the same HD 660S2.
Does the Accentum Sennheiser have noise cancelling?
The HD 660S2, on paper. Its design is specifically built to double sound pressure at the lowest octaves, with a stated range reaching down to 8 Hz. The Accentum's stated frequency range is narrower and its focus is wireless convenience, not sub-bass depth.
You can plug it in — a 6.3mm to 3.5mm adapter is included — but a 300-ohm, open-back headphone really wants a dedicated amplifier to perform at its best. If phone-first, cable-free listening is your priority, the Accentum's Bluetooth 5.2 and 24-ohm impedance are the far better match.
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