Sennheiser HD 620S review: closed back, open sound

Introduction

Audiophiles love to argue over which wired headphones are best, but there’s one thing they can usually agree on: that Sennheiser’s 600-series cans are a sensibly-priced yardstick with which to judge the performance of any rival. The wonderfully neutral tuning and airy soundstage come with one major downside, though – an open-back design that makes them less than ideal for listening to away from home. The Sennheiser HD 620S aims to change that.

The firm reckons these closed-back headphones are as close a match to the rest of the range as it gets, keeping the feeling of openness and space but keeping sound leakage to a minimum. Bass response is apparently even better than the classic HD 600, which has been doing the rounds since 1997, without needing a beefy headphone amp to power its dynamic drivers.

On paper, they sound like a winner – and at $350/£299/€349, they’re sensibly priced to compete with the tough closed-back competition. But can the HD 620S really hold a candle to one of the headphone world’s poster children?

Design & build: where’s the six appeal

The HD 620S doesn’t look like a typical pair of Sennheiser 600-series headphones. They’ve got a much closer family resemblance to the closed-back 500-series, just with metal inserts instead of see-through grilles on each ear cup. The styling is more functional than anything else, and there’s an awful lot of plastic in use here. Not all of it feels as nice as I’d hope given the asking price. Unlike the Momentum wireless range, black is your only colour choice.

The firm has at least upgraded the construction here, with a metal headband that should hold up better to regular use. The HS 620S doesn’t fold or collapse for travel, though, which is a shame given the closed-back design makes these much better for using in public. The ear cups don’t have a huge amount of tilt, either, which can make finding a good seal – crucial for the best bass response – tricky for glasses-wearers or those that wear their headphones over their hats.

A high amount of clamping force isn’t unusual for Sennheiser. The HD 620S put quite a lot of pressure on my head and ears, but the thickly-padded ear cups and headband meant I didn’t find it uncomfortable to wear. Sound isolation is fantastic, but the artificial leather wrapping did mean my ears got pretty toasty after long listening sessions.

Importantly, they do a superb job at preventing your tunes from leaking out, so as not to disturb anyone else nearby.

The ear pads pop off with a reasonable amount of force, and the cable is detachable too. Official and third-party replacements are very easy to get hold of (a benefit of reusing an existing frame), which is good news if you want your gadgets to last as long as possible.

Features: mostly minimal

As I’ve come to expect from Sennheiser headphones, there’s little here in the way of accessories or extras. Inside the box there’s just the HD 620S itself, the 1.8m cable (which ends in a 3.5mm plug) and a 3.5mm to 6.3mm adapter. You don’t get a hard shell travel case for keeping them safe while in a backpack, just a soft cloth bag that’ll only prevent surface scratches.

The cable has a locking mechanism to keep it securely connected to the headphones, and can be swapped for a third-party balanced cable if you plan on hooking it up to a balanced amplifier. The rubberised plastic isn’t the greatest at cutting out cable micro phonics, so moving around can result in audible rustling noises in the left ear. Rivals with braided or fabric-wrapped cables fare a little better here.

These headphones will reportedly work with Sennheiser’s optional inline remote cable, which adds a one-button remote control and integrated microphone for making voice calls. I didn’t have one on hand to verify the claim.

Sound quality: neutral ground

The HD 620S isn’t just a closed-back version of the HD 560S. Sennheiser has fitted these headphones with a bespoke driver, and angled slightly towards your ear canals for greater clarity, and covered it with a very open mesh fabric. The latter was presumably to get as close to the open-backed HD 600 – which was used a reference for tuning – as possible.

Some would say those headphones lacked a bit of sub-bass and bass presence. Sennheiser has certainly addressed that here, with a more impactful low-end – but not one that creeps remotely into boomy territory. It’s very well controlled, coping well with the bouncing bassline of AC13 x Eksman’s POW without intruding on the synths or vocals.

It’s vocals in particular that highlight the definite feeling of openness; the HD 620S simply doesn’t sound as ‘boxed-in’ as many closed-back headphones do. No, it’s not as as airy as the open-backed alternative – but it gets surprisingly close. Audio doesn’t sit as far forward as it does on the Rode NTH-100, and the HD 620S has it beat for high-end precision.

That’s despite Sennheiser having toned down the top-end brightness from the rest of the 600-series, preserving plenty of crispness without becoming sharp-sounding. There’s impressive neutrality here, which will surely please audiophiles. Fans of more v-shaped tone curves will want to shop elsewhere.

Sennheiser HD 620S verdict

There’s no question the Sennheiser HD 620S delivers on tonality. The tuning gets impressively close to an open-back feel, with none of the sound leakage. For that alone, it’s a worthy addition to the decorated 600-series. They’re hopefully built to last, and priced keenly to compete with more dynamic-sounding rivals including the FiiO FT3 and Beyerdynamic DT 770.

I do think styling could’ve been a closer match to its rangemates, though. As it is, this looks like a 500-series model – and some of the materials used don’t match up to the asking price. But for that signature Sennheiser sound in a wired, closed-back body, there’s plenty to like here.

Sennheiser HD 620S technical specifications

Drivers	38mm dynamic (36mm effective, 42mm housing)
Frequency response	6Hz-30kHz
Impedance	150ohms
ANC	No
Connectivity	1.8m cable w/ 3.5mm plug, 3.5mm-6.3mm adapter
Weight	326g