Sennheiser HD 620S Closed Back Headphones Review.

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.