Sennheiser HD 620S

Verdict

Sennheiser eschews the typical open-back design for reference headphones with the closed-back HD 620S, allowing for a small amount of sound isolation against the outside world. They won’t do much on a noisy commute, but the HD 620S headphones offer a little protection for listeners who don’t have a soundproof room at home.

Introduction

Who are the Sennheiser HD 620S headphones for? As wired, reference headphones, they’re designed to cater to listeners after a high-fidelity audio experience, without the compressed data or over-the-air interference of Bluetooth connections. 

On the other hand, while reference headphones typically use an open-back design for a wide soundstage, and the feeling of sound travelling freely around you, the HD 620S sticks to a closed-back design, which limits the soundstage but also allows for a modicum of protection against outside noise.

There’s no active noise cancellation here, and listeners after that should consider our guide to the best ANC headphones. The HD 620S instead acts as a halfway house between real audiophiles and those after a bit of practicality in their audio hardware, offering high quality sound with some basic sound isolation. For some, it may be a perfect compromise.

Design

• Rigid metal headband
• Soft carry case
• No built-in buttons or sensors

The Sennheiser HD 620S headphones are designed for sound, and not much else. There are no built-in buttons or touch controls, with all playback and volume adjustment coming from your source device (exclusively over a wired connection). The cable is 1.8m long, with a 3.5mm connector as well as a larger 6.3mm adaptor you can use to connect to amps and professional mixing desks.

At 670g, the HD 620S has a decent heft, but is light enough to wear for long listening sessions, thanks to substantial cushioning on the ear cups. The headband is made of a rigid metal with adjustable lengths on either side of your head, keeping the headphones stiffly in place where you want them.

The headphones’ casing is made of black plastic, with light pockmarks along the ear cup, which give a slight grip when taking them on or off. A simple cloth bag (included) helps to keep the headphones protected from dust, though not from any knocks if you take them outside.

Specification

• Wired use only
• Uncompressed, lossless audio
• No Sennheiser app functions or built-in controls

This will be quick! These wired headphones outsource any playback to your source device, meaning there are no buttons or touch controls to speak of, and even the official Sennheiser Control app doesn’t sync up with the hardware – there’s little room for EQ adjustment for headphones that are meant for audio fidelity over anything else. (However, it’s possible to use third-party EQ software if you like.) 

Similarly, there are no battery life concerns,.

The main feature here is the uncompressed audio you’ll get over a consistent wired connection, which will be enough for some.

Sound Quality

• Wide soundstage
• Basic sound isolation for noisy homes
• 150 Ohm impedence

For the HD 620S headphones, Sennheiser drew on years of experience making its open-back 500 and 600 ranges, this time with a closed-back limitation. But the audio experience is still so impactful, expansive, and detail-rich that it’s easy to forget you’re not wearing open-back headphones. 

I was mostly impressed with the drivers’ restraint, with tight, controlled notes even at high volumes, and an incredible separation between instruments during classical listening sessions. But even the overlapping voices of modern pop tracks manage to push into audibility without merging or muddying each other.

There’s a real sense of sound moving around you in three-dimensional space, despite these being stereo headphones (without Dolby Atmos or any spatial audio formats). Sennheiser credits the angled baffle behind the 42mm transducers, saying that it “recreates the triangular imaging of a great loudspeaker setup”, directing sound and keeping a firm hand on undesirable vibrations.

No doubt an open back design would extend the soundstage further, but the HD 620S is still a long way away from the cocoon of most ANC headphones, which seek to shut out the outside world entirely.

You’d get a wider 12Hz – 41kHz frequency response and higher 300 Ohm impedance with the Sennheiser HD 650, a step-up open-back model, but the HD 620S capably straddles smooth reference audio with some of the everyday practicalities of at-home listening.

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