For quite some time, I’ve waited desperately for a reasonably priced closed back to make its way into my reach. I watched flagship closed backs such as E3 and Liric 2 hit our shelves this year, which only further whetted my appetite for a closed back that could provide great sound at a lesser cost. After only a few months, Sennheiser announced the HD 620S, a closed back retailing at $349. While Sennheiser closed backs never delivered a sound tailored to my tastes and preferences in the past, will the HD 620S be the one that finally breaks the mold?
Build and Design
The HD 620S won’t catch your eyes from its stunning looks, but it will most likely provide a solid first impression on overall build quality when it's in your hands or on your head. Although the chassis is mostly made of plastic, there's still some design choices, such as the metal driver housing that protects the single dynamic driver inside, as well as the stainless steel headband adjustment mechanism, which make the build feel more premium, and more importantly durable. HD 620S has a clamp force that is quite strong to begin with, but I found that the soft and cushy leather pads, in addition to the padding on the headband, creates a rather comfortable seal. And the inner ventilation with the pads extended my listening sessions by quite a lot by releasing excess heat build up. Additionally, the clamp force seemed to ease up a little bit the more I wore it across multiple different listening sessions. Sennheiser HD 620S encapsulates simplicity and intentionality in its design, with ergonomics as the top focus.
Inside the box, Sennheiser decided to pack light, which is often par for the course for the brand. We get a standard black cinch cloth bag that is meant to protect your headphones from dust or even scratches when the headphones are placed in a bag. Sennheiser HD 620S’ cable is a standard black cable that is 1.8m in length, and is terminated in 3.5mm, though the included 6.3mm adapter can easily be screwed on for ease of source swapping. Luckily, Sennheiser accommodates balanced cable enjoyers by internally wiring the HD 620S to allow for a balanced connection as soon as Sennehiser 4.4mm cable releases, which is to be expected by “mid-summer 2024,” per Sennheiser. Additionally, folks who bought a balanced cable for any headphone they’ve had in the HD5** series won’t need to shell out any extra cash for another balanced cable as they accommodate the same connector type, meaning balanced cables are already in supply if you can’t wait any longer for that balanced connection. Sennheiser HD 620S has a functionally sound unboxing experience that gives you all the essentials needed to get you ready to enjoy your tunes.
Sound
Balanced, spacious, and engaging. Just a few words that come to mind when going over the broad spectrum of sound that the HD 620S portrays in its sonic profile.
For sources used, I bounced around quite a few options, though the convenience of powering the HD 620S off a DAP made my DX180 almost irresistible in my listening sessions, with the majority of my hours logged with this pairing. Of course my Questyle M15 got some love as well, powering the HD 620S easily, and also providing a more thoughtful and referenced listen in comparison to the DX180. And just to really demonstrate how flexible these headphones are, even my Apple dongle got in on the action for some on the move listening. So while a full fledged desktop system will get the absolute most out of this headphone, don’t think the HD 620S can’t join you on a plane or public transportation with a portable source of your choosing.
In the lowend, HD 620S doesn’t entice you with a large delivery of bass, rather a more focused bass response that prioritizes extension, impact, and detail. The intimacy of bass guitars, and the lowest frequencies of the subbass having such prominence is largely in part due to the HD 620S’ closed back design, but bass guitars’ well separated sound becomes rather distinct and demonstrated with excellent clarity, most notably on a track such as “Natural Mystic” by Bob Marley and the Wailers. In combination with the rich and thumping bass guitar, the bass drum has excellent character and resolution to it as well. Those looking for a tsunami of bass with bone crushing dynamics may not find solace in the HD 620S, but those who like proper extension and a more detail oriented bass response will certainly find satisfaction in this bass response.
Sennheiser was able to keep both lower mids, and the entirety of the midrange for that matter, well separated from the bass response, which is a testament to the overall tonal balance of HD 620S’ sound signature. Instruments have great character to them, and the overall midrange tonality is quite soothing and sweet. The general timbre of HD 620S is mostly natural, and there isn’t an obvious sense of warmth, but the midrange doesn’t feel cold or lifeless. Rather, the upper midrange in particular has excellent presence, with vocals carrying serious weight and body to them. A track like “L’Amour De Ma Vie” from Billie Eillish showcases the HD 620S’ not too forward, not too shallow, but just right vocal placement that captures a very complete and cohesive midrange.
The treble is where I’m most critical of Sennheiser HD 620S’ sound signature. At times, I can find it to be quite peaky, with occasional dips that can portray songs in a somewhat dark, dull way. But on the other hand, it can also give solid resolution and decent extension as well, making for a contrasting, and rather inconsistent listen. While HD 620S’ treble began to grow on me the more and more I listened, I do believe this will be listeners biggest point of contention as it occasionally hits the mark just right, or is a soft let down in what is a very refined and structured sound signature otherwise. A song that is usually very energetic in the top end, such as George Michael's “Soul Free,” can come off flat and too smooth to really engage me in all that it has to offer. While this does make some treble intense tracks slightly more digestible, some more air, extension, and shimmer would’ve gone a long way in delivering a sound signature that often performs above its price tag.
As for technical details, Sennheiser seems to have really dialed in the spaciousness that they capture so well in their open backs, here in the HD 620S. “Foxy Lady” by Jimi Hendrix showcases HD 620S’ ability in giving instruments proper spacing, while also having excellent layering that gives a spotlight to whatever instrument you’d like to hone in on within the mix. Whether it's Billy Cox on bass, “Mitch” Mitchell on drums, or the highlight of the show, Jimi Hendrix on guitar and vocals, HD 620S gives a well articulated stage that puts you in the front seat at the show. Its vertical imaging isn’t anything to scoff at either, but HD 620S certainly has more width than it does height.
Final Thoughts
Although HD 620S may not be the first or last closed back you’ll own, it does a lot of things right at a very justifiable cost. And yes, a more resolving treble, rather than the more relaxed and smooth sound of the top end frequencies would’ve been welcomed with open arms. But at its core, HD 620S is a good headphone. After longing for a closed back that meets my needs for quite some time, HD 620S checks all of my desired boxes; comfortable ergonomics, solid all around sound, and the ability to go portable. If this is what you’ve been looking for in a closed back as well, there should be no hesitation in considering the HD 620S as a proper mid-fi closed back purchase.
