Sennheiser HD 620S Review: Closed-back, but with stunningly open sound

Sennheiser’s HD600 series is legendary for serving up some of the best headphones for audiophiles. The range, which goes all the way back to the OG HD600 released in 1997, is known for its extremely high audio quality and wide soundstage, courtesy of its generally open-back design. This open-back design, however, comes with a headache – sound from the headphones often leaks out from the openings in the headphones, and external sound also tends to come in, restricting their use to studios and making them very unsuitable for use in public places.

With its new HD 620S, Sennheiser has attempted to come out with a pair of headphones that deliver the best of both worlds – a truly personal audio experience as well as a wide soundstage. All this without compromising on audio quality.

The Sennheiser HD 620S are closed-back headphones (a rarity in the series) but claim to come with a really wide soundstage. That sounds contradictory, as closed-back headphones generally tend to have a slightly warmer, bassy sound due to their restricted space. Has Sennheiser managed to pull off this audio miracle of sorts? Let’s find out in this Sennheiser HD 620S review.

Sennheiser HD 620S design: Smart, well padded and comfortable

Sennheiser are masters of understated yet elegant headphone design, and the HD 620S are a fine example. Their design seems to be inspired by the Sennheiser HD 560S, with the headband curving to blend into the earcups on either side. The headphones are mostly made of plastic, but the earcup covers and the headband are both steel-reinforced. There is ample padding on the earcups and also on the headband, using special artificial leather with polyurethane, which does not crease. The Sennheiser branding is minimal, with just two tiny logos on the outer part of each earcup.

The earcups do not rotate – they barely move a little back and forth – which means that the headphones cannot be folded into a more compact package. This makes them a little bulky to carry. The right and left cups are marked clearly on the inside of the headband, and the left earcup has a single 1.8-meter cable that ends with a 3.5 mm audio jack and a 3.5 mm to 6.3 mm adapter on top of it. There is a very basic thin cloth carry bag in the box. While it is handy, we do wish Sennheiser had given us something more substantial, as it does for its more mainstream Momentum series of headphones.

Unlike many Audiophile headphones, the HD 620S do not look geeky or large and can actually pass off for mainstream headphones. They weigh about 320 grams without the wire, which is not super light but not crazy heavy, either. It is only when you peer within the earcups that you get a hint of the audio sorcery that these can deliver. The cups are slightly deeper than usual, giving the sound a bit more “air.” Sennheiser also says that the 42 mm transducers (roughly, the drivers) are specially angled.

We found the Sennheiser HD 620S quite comfortable to wear. The heavily padded earcups can get a little warm and sweaty in Indian summers, and the headband clamping is a little on the higher side (perhaps it will loosen with time). All said and done, the HD 620S are that super rare pair of audiophile headphones that will look perfect at home, whether in an office, a cafe, or in a studio. They have an air of relaxed elegance, with their metal components adding some solid feels as well.

Sennheiser HD 620S Performance: Delivering that wide soundstage with very good sound (get a DAC for it, though)

Like all audiophile headphones, the Sennheiser HD 620S are mainly about sound. There is no battery life, call quality, ANC, touch or button controls, or multi-device connections to muck around with. You simply plug the headphones into your audio source, place the headphones on your ears, and listen. Before you do so, remember to get a reasonably powerful digital-to-analog converter (DAC) that can deliver the kind of power that the HD 620S demand. These headphones come with an impedance of 150 ohms. To get an idea of just how much power that is, well, most smartphones cannot handle headphones with an impedance of more than 32-50 Ohms, and even most notebooks would struggle to deliver 150 ohms (even MacBooks prior to 2022 cannot). So our advice would be to invest in a good quality DAC, preferably one with a neutral sound signature, to really get the most out of these headphones. Yes, the HD 620S can work with smartphones, tablets, and notebooks, too, and will sound quite good even then, but their output will be of markedly lower quality, and you will often end up with lower volume.

Once set up with a good DAC (we used the iFi Zen DAC V2) that can support it, the Sennheiser HD 620S deliver an outstanding performance. The big question, of course, is whether they actually provide a wide soundstage in spite of being closed back? The answer to that is: yes, they do. The HD 620S deliver the widest soundstage we have got from a closed-back headphone. We got very close to the classic feeling of being in a room with sound coming from different parts of it. The sheer clarity of the audio and excellent instrument separation often allowed us to actually visualize mentally where each instrument was playing. To be fair, it was not as expansive a soundstage as one gets from classic open-back headphones, including Sennheiser’s own HD 660 or the high-end headphones from BeyerDynamic, but it is still very impressive.

The signature of the HD 620S is largely neutral, making them very good for listening to just about every genre of audio. However, they excel particularly at jazz, country, and classical. Their closed-back design ensures that it has even slightly better bass than you get on most open-backed headphones (which tend to be weak in that department and better at treble). Sennheiser’s mid-mastery is very much evidenced here, with vocals coming to the fore with incredible clarity. These are the kind of headphones where you can hear every small tinkle in an orchestra and even the vibration of a guitar chord in a country number. And with the right DAC, you get very impressive volumes. You can get lost in the sound of these headphones, especially if you are watching shows or films with vivid landscapes – even podcasts and audiobooks sound wonderful, provided they are well-produced. Their clarity makes them an excellent option for professionals, too.

Best of all, their closed-back design means that the people around you cannot hear what you are hearing – there is no sound leakage, unlike open-back headphones. We suspect the higher-than-usual clamping force of the headband might actually be part of an attempt to improve passive noise cancellation. But all said and done, the Sennheiser HD 620S deliver on their promise of delivering a wide soundstage even within a personal closed space. That really puts them in a zone of their own in the Indian market.

Sennheiser HD 620S Review Verdict: A terrific option for audiophiles on the move

The Sennheiser HD 600 series almost always comes with premium pricing, and the HD 620S is no exception. The HD 620S come with a price tag of $300/Rs 32,990. That actually puts them right alongside their open-back sibling, the HD 660S2, which are retailing for Rs 29,990 and actually have a slightly wider soundstage but are not really great for outdoor use.

Those wanting premium-level closed-back headphones might also be tempted by the wood-infused Meze – 99 Classics, which is also priced at close to $300/Rs 30,000, looks beautiful and deliver excellent sound, but like most closed-back headphones, have a warm, bass-accented audio signature. However, the closest thing we have actually seen to the Sennheiser HD 620S is the Beyerdynamic DT1770 pro, which is also closed back but packs in excellent clarity and a surprisingly good soundstage. However, it is not only significantly more expensive at $430/Rs 39,990, but is also more bulky.

What makes the HD 620S special is the fact that they are designed for regular as well as studio use. These are the perfect headphones for the person who values high-quality audio and wants it everywhere, not just in studio or professional conditions. We are not going to say that these replace open-back headphones – those that remain in a special zone – but these prove that you can get a wide soundstage and great sound even in comfortable, closed-back headphones. These are perfect for audiophiles who want great audio wherever they go without being disturbed, be it in the office, studio, or even in a cafe. Just pair these with a good DAC, and no matter where you are. Let your ears get some awesome audio, even as your senses take a stroll in the widest soundstage closed headphones can deliver, without worrying about anyone hearing you or you hearing anyone.

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