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Sennheiser HD 400 Pro

Open-backed Headphones By Sam Inglis
Published February 2022

Sennheiser HD 400 Pro

Sennheiser’s new studio headphones offer some serious bang for your buck.

German audio titans Sennheiser operate across multiple markets, and although they manufacture many headphone models that are widely used in studios, not all of these are officially ‘pro audio’ products. In particular, high‑end open‑backed designs such as the HD 600, HD 650 and HD 800 are categorised as ‘audiophile’ headphones, and marketed mainly at hi‑fi enthusiasts. So, although the new HD 400 Pros are by no means Sennheiser’s most expensive open‑backed headphones, and are more affordable than all the aforementioned models, they could nevertheless be seen as the new flagship of the company’s pro audio range.

For open‑backed headphones, in fact, the HD 400 Pros are aggressively priced, undercutting potential rivals such as the Audio‑Technica ATH‑R70x, Austrian Audio Hi‑X65 and Shure SRH1440, and going more or less directly up against the Beyerdynamic DT900 Pro X. It’s fair to say this price‑consciousness is a little apparent in both the packaging and the industrial design of the HD 400s. They don’t come with a carry case or even a bag, and the frames and earcups are made almost entirely from utilitarian black plastic. The earcups themselves are very elongated, as now seems to be common in headphone design, and offer a relatively small degree of movement in both the fore and aft and the up and down planes. The plastic construction makes them very light at 240g, and the cushions are soft, but they nevertheless clamp quite firmly against the sides of the head. Comfort is a very personal thing, but I would rank the HD 400s only so‑so in this respect.

The HD 400s are fed audio through a removable cable which locks securely into the base of the left earcup. Both straight and curly cables are supplied as standard, and the eagle‑eyed will note that the locking connector is a TRRS mini‑jack rather than the cheaper and more widely used TRS. This means that the left and right channels have independent return paths, in theory reducing crosstalk.

The HD 400s use conventional moving‑coil dynamic drivers, with a large moulded grille allowing sound from the back of each driver to escape into free air. The impedance is quoted as 120Ω, which is higher than most consumer headphones but not so high as to make them hard to drive from standard audio‑interface headphone sockets and the like. Sensitivity is specified at a very decent 110dB SPL for a 1V RMS, 1kHz tone, while total harmonic distortion is 0.05 percent for a 1kHz tone at 90dB SPL.

I was able to compare the HD 400s directly with open‑backed phones from other manufacturers, and came away impressed.

HD Audio

One of the reasons that Sennheiser’s HD 650s are so widely used in mixing is that they have a reputation for being ‘unhyped’: they deliver a flat, neutral, uncoloured sound that allows you to listen to music in an analytical way. I didn’t have a pair of 650s on hand for comparison, but I was able to compare the HD 400s directly with open‑backed phones from other manufacturers, and came away impressed. The Shure SRH1840s, for example, are longstanding favourites of mine, and retail at around twice the price of the HD 400s; yet the HD 400s come pretty close to matching them in terms of neutrality, and sound marginally cleaner on some material. A gentle presence boost is audible somewhere around the 5kHz mark, and the bass is perhaps a touch leaner on the HD 400s, but there’s less to choose between them than the price would suggest. Meanwhile, Austrian Audio’s Hi‑X65s sounded positively ‘scooped’ in comparison, with a recessed midrange and very forward bass and treble.

In short, then, the HD 400 Pros are exactly what a ‘pro audio’ product should be. The overriding sense you get from them is that the development and manufacturing budget has been spent not on cosmetics or accessories, but where it matters — on the sound. Try these and you may not feel you need to spend more.


The HD 400s are neither the most comfortable nor the most stylish pair of open‑backed headphones around, but they are very affordable and sound great.


£219 including VAT.

Sennheiser UK +44 (0)333 240 8185