Headphones

Monitors / Monitoring > Headphones

Published January 2025

The DT 1990 PRO MkII and DT 1770 PRO MkII are essentially open‑ and closed‑back versions of the same design.

The new MkII editions of beyerdynamic’s flagship headphones are outwardly identical to the previous versions. Internally, however, it’s a very different story!

As befits a manufacturer celebrating their centenary, beyerdynamic products tend to stand the test of time. The company’s very first headphones, the DT 48s, were in continuous production from 1937 to 2012, while the still‑current M 160 and M 130 ribbon microphones date back to the 1950s, and the iconic, rectangular DT 100s have been a recording‑studio staple since their introduction in 1965. Any new model that enters the beyerdynamic line‑up has a lot to live up to — and recent headphone launches have done a pretty good job of it.

At the top end of the market, headphone development at beyerdynamic has focused on two proprietary driver technologies called STELLAR and TESLA. In a moving‑coil loudspeaker or headphone driver, a coil of wire is attached to the back of the diaphragm, with a permanent magnet positioned inside it. When the amplified audio signal is passed through the wire, electromagnetic induction does its thing and the diaphragm is pushed and pulled at a frequency determined by the signal.

In the original version of the TESLA driver, the usual geometry was reversed, and instead of locating the magnet inside the wire coil, beyerdynamic used a ring‑shaped magnet that sat outside the coil. This generated a particularly powerful magnetic flux density, with concomitant benefits in terms of sensitivity and low distortion. The TESLA driver was first used in high‑end headphones for the consumer hi‑fi market, but soon found its way into two studio products: the closed‑back DT 1770 PRO and the open‑back DT 1990 PRO. These were introduced in 2016, and have proved very popular despite — or, perhaps, because of? — the fact that they were never reviewed in this magazine.

To celebrate their anniversary, beyerdynamic have introduced upgraded or special edition versions of quite a few products, and their flagship studio headphones are no exception. Both the DT 1770 PRO and DT 1990 PRO are now at MkII, with an updated version of the TESLA driver that is said to improve performance still further.

The new driver, dubbed the TESLA.45, actually reverts to a more conventional structure with the magnet inside the voice coil, but still achieves a flux density in excess of 1T. It also incorporates many of the improvements made in the STELLAR.45 driver used in the DT 700 and 900 PRO X models, while one of the biggest steps forward has been the development of a new diaphragm geometry. In the new TESLA.45 driver, the voice coil is not wound directly onto the back of the diaphragm, but onto a lightweight collar that protrudes outwards. This design ensures that the voice coil remains entirely within the magnet gap even at relatively high excursion levels, delivering greater linearity and lower distortion.

An exploded view of one side of the DT 1990 PRO MkII, showing the new TESLA.45 driver.

Open & Shut Case

The 1770 and 1990 are, respectively, closed‑back and open‑back versions of a design that is otherwise identical. They are manufactured at beyerdynamic’s Heilbronn headquarters in central Germany, and their construction is pleasingly businesslike and serious‑looking, with a ‘none more black’ aesthetic that seems fitting for a professional studio tool. The two models ship in the same lightweight, zip‑up, semi‑rigid case, which is also entirely black and has no identifying features, so if you’re lucky enough to own both models you’ll open the wrong case approximately 50 percent of the time. It would benefit from having a handle, but most importantly, it offers a decent level of protection whilst being much lighter than typical hard‑shell cases.

Within the case, a pouch houses the detachable cables, offering the traditional choice of straight or curly. The former is 3m long and the latter will stretch to 5m. These attach to the base of the left earcup using a mini‑XLR, and to your audio device through the equally time‑honoured mini‑jack with optional 6.5mm screw‑on adaptor. As well as the headphones themselves, both models also come with a second set of earpads. The stock earpads are velour‑covered: in the case of the DT 1990 PRO MkII, they are designated the Producing version, and introduce a small bass boost. The second set supplied with the 1770 have an imitation leather cover and offer greater isolation from external sound, while the alternative Mixing & Mastering earpads for the 1990 are also velour and are intended to flatten the response. (The headband cushion is also replaceable.)

However, swapping earpads isn’t something I’d want to attempt on a regular basis. On paper, or in PDF manual, the process is simple: you snag the elastic band that lines the back of the earpad on a notch in the rim of the earcup, and twist through 360 degrees. If that works first time, it takes a few seconds. But if it doesn’t, the band becomes increasingly stretched and non‑compliant, and it quickly gets frustrating. Having swapped the first one with no fuss at all, it took me nearly an hour to do my second earpad. It doesn’t help that the two sets of earpads for the 1990 are indistinguishable once attached to the earcups.

The physical design of both models is largely conventional, which is understandable since beyerdynamic probably created those conventions in the first place!

Full Strength

The physical design of both models is largely conventional, which is understandable since beyerdynamic probably created those conventions in the first place! The earcups are attached to metal yokes which allow them to pivot through a reasonably wide up/down arc and a rather smaller fore/aft angle. By modern standards, they are on the large side, though still nowhere near as big as something like the Audeze LCD‑X or HEDDphone. Construction feels extremely solid, and at 377 and 376 grammes respectively, the 1770s and 1990s are a little heavier than many rivals, but I found them very comfortable. (In fact, I’ve never experienced any sort of inverse link between weight and comfort in headphones in general.)

It’s always reassuring when manufacturers go beyond what’s expected of them in terms of publishing specifications, and beyerdynamic certainly do so with these two models. In both cases, a frequency response of 5Hz to 40kHz is claimed, though with no tolerances, this isn’t the most helpful figure. But in other respects, the specs are exemplary. Sound pressure levels are quoted both for 1mW and 1V references, and separate THD figures are given for 100Hz, 500Hz and 1kHz signals. These are impressive figures, too: for a 1mW input, both models deliver 0.2% THD at 100Hz and 0.1% or less at the other frequencies. Even the amount of pressure exerted by the headband has been quantified (6 Newtons, if you’re interested), and a meaningful 25dBA measurement for attenuation of external noise is provided for the closed‑back 1770. Both models have a nominal impedance of 30Ω, and the 1770s are, as you’d expect, marginally more sensitive than the open‑backed 1990s, delivering 95dB SPL for a 1mW input at 500Hz to the latter’s 94dB. Both are therefore easy to drive from any source.

Brighten Rock

I have never heard the original version of either model, and in fact my experience of beyerdynamic’s headphones in general is quite limited, so I came to the 1770 and 1990 without any well‑formed expectations. Would they prove ruler‑flat and analytical, or would they offer a more characterful listening experience?

The DT 1990 PRO MkII competes roughly head‑on with the Shure SRH1840, the Neumann NDH‑30 and the Sennheiser HD490 Pro, all of which seem to me to offer plausible if slightly varied interpretations of a subjectively flat frequency response. Out of the box, the beyerdynamic open‑backed model has a gently ‘scooped’ tonality in comparison, with a broad treble boost starting around 5kHz and extending well above 10kHz complemented by a slight bump in the ‘upper bass’ region. As is often the case in open‑backed headphones, genuine sub‑bass is a little subdued in comparison. However, switching from the stock Producing earpads to the alternative Mixing & Mastering ones seemed to me to flatten this lower midrange region appreciably, and I also felt I was less aware of the treble boost with the second set of pads, although it would be impossible to do a proper A/B test without two pairs of 1990s to swap between. On balance I felt that they were still a shade mid‑recessed compared with my personal idea of neutral, but it was a close‑run thing.

The closed‑back DT 1770 PRO MkIIs, meanwhile, have a pleasingly similar overall tonality to the 1990s, but with a slightly more pronounced ‘smile curve’. At the time of writing there are no generic Sonarworks SoundID profiles for either model, and those for the original MkI variants are not a great fit, but I’m sure that inasmuch as they depart from perfect flatness, this will be easily addressed with corrective EQ. Most importantly, there’s something very likeable about the sound of both models just as they are, and although you might expect to find that treble emphasis a little fatiguing, in practice it really isn’t. Music of most types is enjoyable to listen to, with the caveat that super‑deep bass is not really the forte of the 1990, and the open‑back model in particular seems to me a very useful analytical tool for mixing, editing and other studio tasks.

Ask An Acoustician!

The refreshed MkII editions of the DT 1770 PRO and DT 1990 PRO headphones are outwardly identical to the original versions, and their physical design is unchanged. Internally, however, both use a completely new driver dubbed the TESLA.45. This driver was the result of a lengthy development process at beyerdynamic, in which Acoustic Engineer Ante Mihalj was deeply involved. I had the opportunity to quiz Ante about exactly what is involved in creating a new pair of high‑end studio headphones.

The new driver draws on ideas from both the previous TESLA driver, as used in the older 1770 and 1990, and the STELLAR.45 driver developed for the PRO X models. “The original idea was to develop a new driver where we can implement the know‑how we have got during the STELLAR.45 development and from the old TESLA models. The first goal was to make a perfect driver, for the next generation of headphones. We didn´t plan making the driver for the DT 1770 PRO and DT 1990 PRO MkII. At first, we thought we would make a new hi‑fi headphone, but in the end we came to the conclusion that we should do it for our high‑end pro audio headphones.”

One of the distinctive features of the previous TESLA driver was the use of ring magnets with the voice coil located inside them. For the TESLA.45, however, beyerdynamic found a way to achieve the same high magnetic flux density using the conventional arrangement with the magnet inside the voice coil. “We used the same configuration as in the STELLAR.45, but thanks to strong neodymium magnets it was possible to achieve a flux density in the magnetic gap of over one Tesla. So even without a ring magnet we got an extremely efficient driver. It’s much more practical for us this way and it enables us to increase the consistency of the quality even more.

“We are using highly automated and extremely precise production processes with the STELLAR.45 and now with the TESLA.45. It was a big project here at beyerdynamic when we developed the STELLAR.45 and we wanted to benefit from this production process technology with the TESLA.45. Since it is being assembled on the same machines, we had to change the magnet configuration. But in the end, we still get a better performance acoustically and have the possibility to improve the production process and get a much higher‑quality driver at the end.

A key advantage of the TESLA.45 driver design is that it can be manufactured using beyerdynamic’s advanced automation systems.

“Our main target for this project was to optimise the membrane behaviour in the low‑frequency range, while considering the overall performance across the whole frequency range. We had quite a lot of iterations where we were making improvements on the THD in the low‑frequency range, but sometimes we had to go a few steps back and compromise the perfect THD performance, to improve the frequency response in the upper frequency range. We went through multiple optimisation loops until we were satisfied with all of the results!”

One desideratum for the new TESLA.45 driver was that it had to work equally well in the closed‑back DT 1770 PRO MKII and the open‑back DT 1990 PRO MKII. There is a certain amount of tension between these two goals, as Ante explains. “For an open‑back headphone, we need a low resonance frequency, whereas a closed‑back headphone would work pretty well with a higher resonance frequency, which comes with some other benefits. The foil material we are using is made from multiple layers, and one of those layers acts as dampening. If you increase the thickness of this dampening material, you get better control of resonances in the high‑frequency range, which is desirable. On the other side, you also get a higher resonance frequency in the low‑frequency range, which doesn’t suit an open‑back headphone. Thanks to the additional bass port, even in combination with a high resonance frequency of the driver, a closed‑back headphone can still achieve a great bass response.”

Low‑frequency performance is also strongly affected by the design of the earpads, which is why both models are supplied with two different sets. “Mostly we are aiming to keep the performance above 500Hz the same with the two earpad variants. The complex nature of the earpads does lead to additional differences in the rest of the frequency response, which are mostly negligible. The balance between bass and the upper frequencies is crucial for the sound signature. So if we just lower the bass a little bit with one of those earpads, we get a different‑sounding headphone.

“You can modify the sound by choosing different foam types or the geometry. Geometry plays a big role in that regard. For example, the DT 1990 PRO MkII earpad with more bass has 20 small holes in the earpad. The earpad with less bass has only four holes in the earpad. It’s completely counterintuitive because you think the bass should be able to escape more easily thanks to more holes, which will result in less bass reproduction, but it’s quite the opposite because we use foam materials with different flow resistances.”

Historically, beyerdynamic have made headphone models with a widely varying range of impedances, to suit different use cases. Like most modern headphones, the DT 1990 PRO and DT 1770 PRO MkII are low‑impedance models, presenting a nominal 30Ω to the source. “We, at least at beyerdynamic, can divide the impedance question into two parts. The first one is the impedance: the resistance of the wire, how many turns in the winding or what kind of diameter we use for the voice coil itself. And this has an impact on the sound, in combination with the amplifier.

“On the other side we have different driver configurations. For example, the older 32Ω, 250Ω and 600Ω drivers from the DT 880 PRO or DT 990 PRO have a three‑piece configuration. The voice coil is attached to a former, and this former is then attached to the membrane. But the STELLAR.45, the 80Ω and the rare 16Ω drivers have a two‑piece configuration, where we glue the voice coil directly onto the membrane. The difference between those two configurations is that with a two‑piece voice coil, part of the voice coil windings are outside of the magnetic gap, while the voice coil of a three‑piece configuration is mostly completely inside the magnetic gap, driving the membrane with a constant force, keeping the THD low. Thanks to less voice coil wire being needed, the moving mass is lowered, resulting in better high‑frequency and transient reproduction.

“With the TESLA.45 we have also extended the magnetic gap height, which increases the maximum excursion of the voice coil, while keeping a constant magnetic field. This way the driver doesn’t generate additional THD and intermodulation distortion, even at high SPLs.

“And for the second part, the impact of headphone impedance in combination with the amplifier, the damping factor of this system is important. We have been thinking about which way to go, and in the end, we realised that a lot of new equipment has a low output impedance. Most headphone amps have an output impedance below 1Ω. And even in combination with a 30Ω driver, that gives you a high damping factor.

“For example, if you compare a tube headphone amplifier, with an output impedance of 50Ω, in combination with a 600Ω headphone, you get a damping factor of 12. But with the 30Ω headphone in combination with an output impedance of 1Ω, you get a factor of 30. And bigger is better in this case, to get less coloration of the frequency response.”

The choice of wire for the voice coil is also an important factor in the design of a headphone driver — which, in an ideal world, would have zero mass. As described above, the three‑piece design of the TESLA.45 reduces the size of the voice coil; in comparison to the original TESLA driver, beyerdynamic achieved further mass reduction by using CCA or copper‑clad aluminium: “The CCA wire comprises an aluminium core with a copper‑clad surface, since copper is a much better conductor than aluminium. We still get a low‑resistance voice coil, but the weight is reduced drastically. The wire we use in the TESLA.45 driver is slightly thicker than in the old TESLA driver, but thanks to an aluminium core, we get a lower‑mass voice coil. This enabled us to decrease the moving mass of the driver even more.”