If you have spent any time in a studio, you have seen both kinds of headphones without necessarily knowing why there are two. Some seal tightly around your ears and block out the world. Others have visible grilles on the outside, leak sound everywhere, and let you hear the room around you. It looks like a small design difference. In practice it changes what the headphones are actually good for, and picking the wrong type for the job is one of the most common mistakes in home studios.

Open-back headphones are the ones engineers reach for when they need to make decisions about a mix, and Beyerdynamic has been building some of the most recognised examples in the world for decades. This guide explains what open-back actually means, why it suits mixing and mastering but not recording, and then compares four of Beyerdynamic's open-back models — the DT 990 PRO, DT 990 PRO X, DT 900 PRO X and DT 1990 PRO MKII — so you can work out which belongs on your desk.

The difference is exactly what the names suggest, and it is all in the outer housing of the earcup.

Closed-back headphones have a sealed, solid outer shell. Sound produced by the driver has nowhere to go except into your ear, and outside noise struggles to get in. That seal is the whole point: isolation in both directions.

Open-back headphones have a perforated grille or mesh on the outside of the earcup, so the back of the driver is open to the air. Sound radiates outwards as well as inwards, and the outside world comes through. Anyone sitting near you can hear what you are listening to, and you can hear them.

That single design choice cascades into everything else. A sealed cabinet traps air behind the driver, which affects how the driver moves and often creates a stronger, more contained bass response, but it can also build up internal reflections that colour the sound. Leaving the back open removes that trapped pressure and those internal reflections, which is why open-back designs tend to sound more natural and less "boxed in."

Three characteristics come up again and again with good open-back headphones.

A wider, more natural soundstage. Because sound is not sealed against your head, the stereo image tends to feel more spacious and more like listening to speakers in a room. Instruments feel placed rather than stuck between your ears.

A more honest, less coloured response. Removing the sealed chamber removes a source of resonance and reflection, so open-back designs generally give a cleaner picture of what is actually in the recording.

Less listening fatigue. Open-backs do not create the pressurised, sealed-in sensation that can make long sessions uncomfortable. They breathe, literally and sonically, which matters when you are working for hours.

The trade-offs are equally clear: no isolation at all, meaningful sound leakage, and usually less low-end punch than a comparable closed-back.

Put those characteristics together and you get the ideal tool for making decisions.

When you mix, you are judging balance, placement, depth and detail. A wide, natural soundstage lets you hear where things sit in the stereo field. A more honest response means you are reacting to the actual recording rather than to the headphones' own character. And low fatigue means your ears stay reliable deeper into a session, which is when most of the important decisions get made.

Mastering demands even more of that honesty. You are making small, high-stakes adjustments across the whole mix, and you need to hear problems, not have them smoothed over. Open-back headphones are unforgiving in the way a good reference should be.

The leakage that makes them useless elsewhere simply does not matter here. If you are sitting alone at a desk, who cares that sound escapes?

This is where people get caught out, so it is worth being blunt.

If a singer wears open-back headphones while recording, the backing track leaking out of those earcups will be picked up by the microphone in front of them. That is called bleed, and it ends up permanently baked into your vocal recording. You cannot remove it later. In the worst cases it causes a hollow, phasey quality in the vocal track, or an audible ghost of the click track underneath the performance.

The same applies to recording acoustic guitar, drums with a click, or anything else where a live microphone shares a room with the headphones.

For tracking, use closed-back headphones. Their seal keeps the backing track in and stops the mic hearing it. Beyerdynamic's own DT 770 PRO is the classic example, and many studios keep closed-backs for the live room and open-backs for the mixing desk. If you can only afford one pair and you record vocals regularly, buy closed-back first. If you mostly mix, buy open-back.

Beyerdynamic is one of the oldest names in the business. Founded in Germany in 1924, the company celebrated its 100th anniversary in 2024, and it has been building professional headphones for most of that history. Its products are still developed and manufactured in Heilbronn, Germany, which is a rare thing at this price level.

The DT designation (from Dynamic Telephone) covers the professional studio line that made the brand famous. Models such as the DT 770 PRO (closed) and DT 990 PRO (open) have been fixtures in studios, broadcast facilities and bedrooms for decades, largely because they are comfortable, durable, easily repaired with replaceable parts, and consistent enough that engineers know exactly what they are hearing.

Two driver technologies matter for this comparison. Tesla drivers are Beyerdynamic's high-end designs, named for the magnetic flux density they achieve, and they sit in the premium DT 1770 and DT 1990 families. STELLAR.45 is the newer 45mm driver developed for the PRO X series, built with a three-layer diaphragm with an integrated damping layer, and deliberately given a low impedance so the headphones perform well from laptops and interfaces without a dedicated amplifier. In 2024 Beyerdynamic introduced the further-developed TESLA.45 driver for the MKII generation of its premium models.

Beyerdynamic DT 990 PRO is the long-standing classic, and probably the most recognisable open-back studio headphone in the world. It is best known in its 250-ohm version, an open, circumaural design with soft velour pads and Beyerdynamic's familiar build. Its sound signature is famously spacious with a lift in the treble and a lift in the bass, which makes detail and air jump out. That brightness is exactly why some engineers love it — flaws, sibilance and harshness have nowhere to hide — and why others find it fatiguing. The one practical catch: at 250 ohms it is a high-impedance headphone, so it really wants a proper headphone amplifier or interface output to reach its potential. Plugged into a phone or a weak laptop jack, it will sound thin and quiet.

Beyerdynamic DT 990 PRO X is the modern reinterpretation of that classic. It uses the STELLAR.45 driver and drops the impedance to 48 ohms, meaning it is easy to drive from just about anything, including a laptop or a modest interface. It keeps the DT 990 character — brighter presentation, wide stereo stage, that revealing quality that exposes problems in a production — while adding contemporary conveniences such as a detachable miniXLR cable (a genuine upgrade, since cable failure is the most common way headphones die). Frequency range is quoted at 5 Hz to 40 kHz. Choose this if you want the classic 990 flavour without the amplifier requirement.

Beyerdynamic DT 900 PRO X shares the same STELLAR.45 driver and the same 48-ohm impedance as the DT 990 PRO X, so on paper they look almost identical. The difference is the tuning, and it is the single most important distinction in this whole article. According to Beyerdynamic, the DT 900 PRO X is voiced more neutrally and linearly across the frequency spectrum, with smoother, tamer treble, specifically so you can mix, master and edit for long stretches without fatigue. The DT 990 PRO X, by contrast, is the brighter, more analytical, more "exciting" of the pair. Same hardware, different intent.

Beyerdynamic DT 1990 PRO MKII is the flagship open-back, launched in October 2024 as part of the new MKII generation. It uses the newly developed TESLA.45 driver, with a structurally optimised diaphragm that improves distortion and impulse behaviour over the original DT 1990 PRO. Impedance is 30 ohms, making this premium headphone remarkably flexible across playback devices — a notable change from the high-impedance tradition. It targets the highest resolution, lowest distortion and best transient response in the range, aimed squarely at professional mixing, mastering and editing. If your work justifies the investment, this is the reference-grade option.

Tuning descriptions follow Beyerdynamic's own positioning; your perception will also depend on source, material and personal preference.

Choose the DT 990 PRO if you want the studio classic at the most accessible price and you already have an interface or headphone amp that can drive 250 ohms properly. It is a proven, revealing reference that has earned its reputation.

Choose the DT 990 PRO X if you love that bright, spacious DT 990 character but want it to work properly straight out of a laptop or interface, with a detachable cable for longevity. Its brighter presentation is genuinely useful for spotting flaws, editing, and detailed work.

Choose the DT 900 PRO X if your main job is mixing and mastering and you want the most neutral, least fatiguing option of the pair. If you routinely work long sessions, this is the smarter buy of the two PRO X models.

Choose the DT 1990 PRO MKII if you are working professionally and want the highest-resolution reference Beyerdynamic offers in an open-back, with the newest driver technology and an impedance that works anywhere.

And remember the one rule that overrides all of this: whichever you choose, keep a closed-back pair for tracking. These are mixing tools, not recording tools.

Open-back headphones are not better than closed-back headphones; they are built for a different part of the process. They give you space, honesty and comfort when you need to make decisions, and they leak like a sieve when you need isolation. Understanding that distinction will improve your recordings more than almost any other purchase.