Sennheiser HD 620S Closed Back Headphones Review.

In fact, way back in my college days I worked at a commercial classical station, and it was my first introduction to the unique Sennheiser sound, in this case, the revered HD414 headphones that were popular with broadcasters. It was my first exposure to an open-back headphone, and I was smitten.

Now, I’ve been able to spend some time with the new Sennheiser HD 620S headphones, a rare closed-back design for the company, and I was anxious to see how the company does with a different, but popular design in the wider market. It also gave me a chance to compare these phones with other Sennheiser headphones I have on hand and some of the other closed-back headphones I have around the house.

The HD 620S is what I would call a mid-fi design and price, retailing for $349.95. They have easily accomplished one of their design goals, and that’s to sound like many of the Sennheiser open-back designs, which is no easy task. They are pretty comfortable, nicely constructed mainly of plastics, and don’t cause fatigue easily.

I’ve lost count of how many headphones Sennheiser has created over the years. Most have been highly rated. The company was founded in 1945 by Fritz Sennheiser, starting in a farmhouse near Hanover, Germany. Early work by the company included microphone design, and its early products were acclaimed. Some of their microphone designs from the 60s are still sold today.

The HD414, which I used during my broadcasting days, was for a long time, the best-selling headphone of all time. Sennheiser has a lot of experience in designing transducers, and you can hear that experience when you listen to their products.

The HD 620S is an attempt to offer a closed-back headphone that sounds open. They wanted a headphone that lets you listen distraction-free, without sound leaking in from your listening environment. With an open baffle and angled transducers, the goal was to replicate the experience of listening to speakers, while keeping the sound inside the headphones, and not leaking into the room.

Toward that end, Sennheiser says it offers “Reference-grade 42 mm angled transducers with 38 mm diaphragm delivers speaker-like imaging with natural detail retrieval and expansive soundstage.”

Sennheiser touts the original design of this headphone, including the angled drivers. Per Sennheiser, the HD 620S features an ultra-light 150-ohm aluminum voice coil for enhanced clarity and accuracy in audio reproduction, along with a lightweight chassis with steel-reinforced headband sliders and artificial leather ear pads with internal venting for long-term durability and all-day comfort.

There’s a lot of plastic on the phones, but they still seem to be sturdy and well-built in use. The ear cup housings and headband sliders are made of reinforced steel and look like they will take a beating. The rest of the headphones are black plastic, but they also seem sturdy. There’s just one cord that connects to the left earpiece, which I think is an improvement over having a split cord. There’s less to get tangled.

Unfortunately, the cord is not a typical plug used in the industry and is not a simple plug-in. You must twist the cord counterclockwise to remove it, and clockwise to put it back in. I wonder how many new owners damage the plug or the phones trying to just pull it out.

The ear cups are synthetic leather, which gives a good seal and are comfortable to wear for extended listening sessions. The headband itself is padded, with what appears to be memory foam.

The cable comes with a 3.5mm jack and an adaptor for people who have equipment that wants the 6.5mm variant.

The cable is light in weight, and as mentioned, having a single cable drive both ear cups can save you some snags. There is an option for a 4.4mm balanced cable, shipping mid-summer 2024.

The Sennheiser HD 620S comes in a cardboard box: inside are the headphones, cord, plug adapter, a quick start guide (comprehensive but small print), and a bag with a drawstring for travel. It’s not going to offer much protection, and I’d prefer all headphones come with a sturdy case, but that’s not what Sennheiser offers with the 620S.

There is no setup really. Decide what plug to use, put them on, and get lost in your music.

I wasn’t sure what to expect. I have a long history with Sennheiser products, and I expected these to sound competitive. But Sennheiser, well known for open-back headphones, was now competing with closed-back designs. At the same time, Sennheiser says these HD 620S headphones emulate open-back sound but provide isolation.

I thought a good comparison would be one of my reference headphones, the Focal Clear Mg headphones. They are an open-back design, and I think are excellent for all types of music, with deep but not over-emphasized bass, and very smooth highs and midrange fidelity.

When I put the Sennheiser HD 620S on I was surprised by a couple of things. For mid-priced headphones, they sounded very good. No obvious defects in frequency range or voicing. While the headphones isolated me from room noise, including an air conditioning unit and a ceiling fan, they provided a wide soundstage, more like what I would expect from an open-back design.

Compared to the Focal Clear Mg, I found the width of the soundstage comparable. Vocalists were well centered on both pairs of headphones when they were recorded to be center stage.

Separation was good, and I found the two headphones very close overall, even though the Focal Clear Mg retails at around $1500.

After extended listening and listening to some sample music on HIFIMAN headphones, older Sennheisers, and a Beyerdynamic headphone, I have to say the HD 620S was roughly competitive, even with more expensive headphones. Still, it’s a solid mid-fi, not a high-end product, and I’ll talk about those details in my specific listening tests and my conclusions.

Here’s some of the music I listened to and my specific evaluations:

At the price point of $349.95, these are excellent headphones and very musical. I haven’t heard anything at the price that will beat them.

To a degree headphones are a matter of taste. Wired, wireless, open back, closed back. Sennheiser is trying to split the difference here, giving what it claims is open sounding headphones, in a closed-back design that gives you privacy and deadens noise from your environment.

I think they’ve largely succeeded in their goal of bringing an open sound to a closed design. Comparing these headphones to other open-back designs, and some earlier Sennheiser open designs, I didn’t think the HD 620S was giving anything up to what an open-back design brings.

Imaging was good, and even playing massed choral works or jazz presented a believable soundstage with no hole-in-the-middle effect. The HD 620S headphones don’t give the ‘orchestra playing inside your head’ effect that many headphones do. The music seemed forward of my head and presented a realistic left-to-right image. In summary, Sennheiser was able to pull off an ‘open headphone sound with a closed design by carefully designing the ear cups and transducers.

Still, in my observation of more expensive headphones, these are mid-fi phones, that don’t compete in frequency response at the extreme ends of the musical spectrum with other, more expensive, headphones from Sennheiser, or my Focals, HIFIMAN, Meze, and others.