The German brand recently unveiled its very first closed-back headphones in the HD600 range: the Sennheiser HD 620S. Although they feature a closed design, they promise a natural sound with the open soundstage for which HD600 headphones are renowned. They also guarantee optimum comfort thanks to their lightweight structure and padded headband. Priced at €349, do these latest-generation hi-fi headphones live up to their promise?
Included accessories
The Sennheiser HD 620S headphones come with a proprietary 2.5mm mini-jack to 3.5mm mini-jack cable (headphones) and a 3.5mm mini-jack to 6.35mm jack adapter. There’s also a soft fabric storage pouch. Given their closed-back (and therefore potentially portable) design, we would have preferred a rigid case to ensure better protection during transport. All the necessary documents are included.
Presentation
Design and comfort
The design of the Sennheiser HD 620S over-ear headphones bears some resemblance to the Sennheiser HD569 model, notably in the shape of the headband and earcups. The finish is different, however, with the texture on the sides of the cups, making the Sennheiser HD 620S more understated and elegant.
There’s also padding on the headband and ear pads, bringing the quality level closer to that of the HD600 range. The adjustable headband is reinforced with metal for greater durability, while remaining easy to handle for more comfort. What’s more, weighing in at just 326 grams, these headphones can be worn for several hours without discomfort. One minor drawback is that the HD 620S’ ear cups don’t swivel flat, which can make them relatively cumbersome when on the go.
In addition, the generously padded ear pads and headband ensure a comfortable fit. However, the pads barely touch the skin near the jaw, which can lead to problematic sound leakage for a closed-back model. It’s important to note that this experience was not shared by the entire editorial team. Comfort and acoustic isolation can therefore vary according to the user’s head shape.
Finally, the synthetic leather pads provide excellent passive isolation. Although they can make your ears warm during prolonged listening sessions, they feature internal perforations that help dissipate heat more effectively.
Acoustic design
Above all, the HD 620S benefit from a closed-back design that makes these headphones a portable hi-fi model. This provides effective passive isolation, ideal for immersive, distraction-free listening. What’s more, it offers complete privacy while you listen, so as not to disturb those around you.
The Sennheiser HD 620S hi-fi headphones feature 42mm transducers with a 38mm diaphragm and an ultra-light aluminum voice coil. They guarantee excellent impulse response and ultra-low distortion across the entire frequency spectrum, from 6Hz to 30kHz. They are tilted backwards slightly, so that they are positioned in front of the auricle of each ear. This design also improves air circulation and reproduces the spacious sound signature of open-back headphones.
With an impedance of 150 Ω, the Sennheiser HD 620S are ideal for audiophiles with a dedicated headphone amplifier or DAC, capable of delivering the power needed to enjoy the very best performance. A sound pressure level (SPL) of 105 dB at 1kHz ensures a powerful, dynamic sound reproduction. What’s more, with a total harmonic distortion (THD) of less than 0.05% at 1 kHz/90 dB SPL, the listener enjoys great sonic clarity, even at high volume levels.
Unbalanced cable
The cable supplied with the Sennheiser HD 620S features a proprietary lockable 2.5mm plug. During installation, it is plugged into the left earpiece of the headphones and must be turned to lock, otherwise the connection will be faulty. This lockable one-sided configuration guarantees a secure connection that prevents accidental disconnection and ensures a stable, reliable audio transmission. Note that the left earpiece features three Braille dots to help the user easily distinguish which side is which.
At the other end of the cable is a 3.5mm mini-jack connector. It can be fitted with the supplied 6.35mm adapter to connect a wide range of sources. Note that options with microphones are also offered by the brand. However, you’ll have to wait a little longer to enjoy a balanced connection, as the brand has announced the release of a 4.4mm cable this summer.
Key specifications
- Closed-back headphones
- Over-ear
- 42mm dynamic transducer with 38mm diaphragm
- Frequency response: 6Hz to 30kHz
- Impedance: 150 Ω
- Total harmonic distortion (THD): < 0.05% (1 kHz/90 dB SPL)
- 1.8m unilateral 3.5mm mini-jack cable + 6.35mm jack adapter
- Weight (excluding cable): 326g
Configuration
To test the Sennheiser HD 620S hi-fi headphones, we paired them with the FiiO R7 headphone amplifier and the Naim Uniti Atom Headphone Edition. We also plugged the headphones directly into a computer’s 3.5mm headphone port and into the Audioquest DragonFly Red DAC. We listen to Hi-Res tracks via Qobuz.
Listening impressions
Sennheiser is right: the HD 620S headphones have a more open, spacious sound than most closed-back models. On all the tracks we listened to, we enjoyed a wide soundstage. On Billie Eilish’s track bad guy, there was plenty of detail. The artist’s voice unfolded with amplitude and realism, giving the impression that she was standing right in front of us. The bass was impactful and gave the music energy.
On the track Only the Lonely, the Sennheiser HD 620S headphones revealed good spatial imaging. Each instrument found its place without encroaching on Tierney Sutton’s vocals. They had a balanced sound signature, with bass that was pronounced, but never exaggerated and always well controlled. Everything was very natural and detailed. The overall sound was smooth, and no fatigue was felt after several hours of listening.
Unlike the headphones in the HD 600 range, bass extension has been improved. This model offers a richer sound reproduction, making it suitable for various genres such as jazz and classical, as well as rock, rap and pop. This enhancement also gives it greater versatility, making it ideal for games and movies. As well as music lovers, gamers can also choose the Sennheiser HD 620S to immerse themselves in video game soundtracks. Footsteps, the position of a competing car, gunshots… The gamer benefits from a wealth of sonic details that gives them the edge when it comes to spotting enemy players.
Finally, the Sennheiser HD 620S headphones offered good passive isolation. Surrounding noises were barely, if at all, audible, and the volume had to be turned up very high for people in the vicinity to hear the music.
Sennheiser HD 620S compared with HD 660S2
The Sennheiser HD 660S2 headphones are open-back over-ear headphones, while the HD 620S are a closed-back model. The HD 660S2 offers a wider soundstage and a smoother overall listening experience. In contrast, the Sennheiser HD 620S headphones offer better bass extension. What’s more, with an impedance of 150 ohms, they are easier to power than the HD 660S2, whose impedance reaches 300 ohms.
Who are they for?
The Sennheiser HD 620S hi-fi headphones will appeal to those looking for closed-back headphones offering good isolation while retaining an open, spacious sound. They are ideal for music lovers, but also for gamers seeking greater immersion in the world of their favorite game. Thanks to their 150-ohm impedance, they’re easier to power than the rest of the HD600 range.
Conclusion
The Sennheiser HD 620S headphones deliver on their promise: they open up the soundstage nicely, while providing effective passive isolation. They deliver a sound that’s inviting, warm, detailed and smooth, making them highly enjoyable for long listening sessions, whether for music or games.
We liked
- The width of the soundstage
- The dynamic sound
- The value for money
- The robust construction
We would have liked
- A balanced cable
- A hard carrying case
