Beyerdynamic DT 700 Pro X & DT 900 Pro X

How do Beyer’s new studio cans compare with the competition?

In his review of the Sennheiser HD 400 Pro headphones back in February (https://sosm.ag/hd-400-pro), Sam Inglis mentioned a direct competitor, in the form of the Beyerdynamic DT 900 Pro X. And as if by magic, I now have a pair of said Beyerdynamic headphones in my review sights, along with their closed‑back sibling the DT 700 Pro X. To complete the circle, I also have Sam’s review pair of Sennheiser HD 400 Pro, as well as a pair of Sennheiser HD 650s, for reference and comparison. It’s in danger of looking more like a headphone party than a review.

The open‑back DT 900 Pro X and closed‑back DT 700 Pro X are very closely related. Not only do they retail at the same price and incorporate the same newly developed 45mm‑diameter ‘Stellar.45’ driver, they share the same mechanical design and much constructional and material detail. And one of the first things that strikes about them is the high quality of those constructional materials and details. There’s something grown‑up and professional about their use of metals rather than plastic, for instance, and where components are plastic, their silky black finish is good to the touch and faultless in appearance. Unusually at the relatively affordable price level, the DT 900 Pro X and DT 700 Pro X are manufactured in Europe rather than the Far East. There’s also a good‑quality feel about the accessories supplied and the entirely recyclable cardboard packaging, too. Those accessories I mentioned include 1.8m and 3m cable options, a drawstring travel bag and a 6.3mm to 3.5mm jack adaptor. The cables, while I’m in the vicinity of that subject, attach to the left earcups using a smart, locking mini‑XLR‑style plug and socket. Beyerdynamic say that almost all of the headphones’ components are replaceable.

The possible downside of heavyweight construction is just that: heavy weight. The DT 900 Pro X and DT 700 Pro X are, respectively, 105g and 110g heavier than the Sennheiser HD 400 Pro, and in the context of a pair of headphones, that is a big difference. Having said that, there’s a lot more to headphone comfort than weight, and I’ll get around to discussing how the DT 900 Pro X and DT 700 Pro X feel on the head a little further down the page. In the meantime there’s some more technical description to cover.

The closed‑back DT 700 Pro X.

Specs

The DT 900 Pro X and DT 700 Pro X are of course simple wired passive devices, and sharing the same driver means they boast the same published technical spec in terms of impedance, sensitivity and frequency response. The ‘Stellar.45’ driver, say Beyerdymanic, incorporates a three‑layer sandwich‑construction diaphragm, the filling of which comprises a damping layer. The diaphragm is driven by a neodymium‑iron‑boron magnet and copper‑clad aluminium voice coil. One of the most important numbers in the DT 900 Pro X and DT 700 Pro X specs is the headphones’ nominal 48Ω impedance, because that partly defines how easy or difficult they will be to drive. Forty‑eight Ohms is on the slightly low side of typical, which suggests good headphone sensitivity; considering that they’re intended for recording and mixing duties where they will most likely be driven from a DAW interface headphone amp, it is a good compromise. Having said that, I’d be slightly wary of using the DT 900 Pro X or DT 700 Pro X with an elderly smartphone or laptop that has limited current delivery and/or a high output impedance.

Diagram 1: The measured impedances of the Beyerdynamic DT 900 Pro X and DT 700 Pro X (purple and red, respectively), and Sennheiser’s HD 400 Pro (blue) and HD 650 (brown).

Speaking of headphone impedance, as with that of passive monitors, it varies significantly across the audio band. This is no great surprise, as the fundamental architecture of a moving‑coil headphone driver is much the same as that of a speaker driver. The specified ‘nominal impedance’ quoted by headphone manufacturers is typically the minimum value. To illustrate this I used a simple piece of audio test gear (a Dayton Audio DATS V3) to measure the impedance curves of the DT 900 Pro X and DT 700 Pro X and the previously mentioned Sennheiser models. The results can be seen in Diagram 1. The purple and red curves are the DT 900 Pro X and DT 700 Pro X respectively, and their measured minimum impedance of 50Ω agrees reasonably well with the specified 48Ω. For comparison, the brown and blue curves are the Sennheiser HD 650 and HD 400 Pro respectively. Again, their minimum measured impedance agrees pretty well with their published specs. It’s noticeable that the Sennheiser models have significantly higher impedances, much higher in the case of the HD 650 — a model clearly not really suited to being driven by smartphones.

Along with measurements illustrating headphone impedance, I’ve also included a set of four FuzzMeasure headphone frequency response measurements in Diagram 2. These measurements were created by pressing a Neumann KU100 ‘dummy head’ into headphone measurement service. The DAW interface was a Focusrite Scarlett 18i20 and the output level was at comfortable monitoring volume. This measurement technique won’t result in definitive headphone frequency response curves, not least because the KU100 is designed for binaural recording, so will imprint a nominal human ear frequency response onto the headphone response (the 8kHz to 9kHz suck‑out in particular is a KU100 artefact). However, the curves are interesting I think for general ‘tyre kicking’ comparative purposes. The red, orange, green and purple traces are the Sennheiser HD 650, Sennheiser HD 400 Pro, Beyerdynamic DT 900 Pro X and DT 700 Pro X respectively. The first characteristic apparent is comparative headphone sensitivity. The Beyerdynamic DT 900 Pro X and DT 700 Pro X are the most sensitive, which, given their lower impedance, isn’t a huge surprise.

Diagram 2: The four headphones’ frequency responses compared. Measurements were taken using a Neumann KU100 binaural dummy head.

The Beyerdynamic DT 900 Pro X and DT 700 Pro X response curves are also quite similar to each other, which again isn’t a surprise, considering they use the same drivers. However, the closed‑back DT 700 Pro X response has a few more lumps and bumps and is the less tidy of the two. Since the drivers are the same, I wonder if these frequency response perturbations in the DT 700 Pro X are a direct result of the closed‑back architecture, which makes it difficult to avoid some of the energy radiated from the back of the driver reflecting back and causing response anomalies. The frequency response of the two open‑back Sennheiser models is similar in terms of general trends to the Beyerdynamics, with the HD 400 Pro showing a particularly linear characteristic though the midrange and the HD 650 showing the falling high‑frequency response that might be expected given its reputation for a warm, natural and un‑hyped subjective balance.

Diagram 3: A waterfall plot of the DT 900 Pro X.

It’s unusual to have open‑back and closed-back versions of essentially the same headphone design to compare, so I’ve included some further FuzzMeasure data to illustrate further how the 900 and 700 differ. Diagram 3 (DT 900 Pro X) and Diagram 4 (DT 700 Pro X) are ‘waterfall’ plots derived from the same KU100 ‘dummy head’ measurements that generated the frequency response curves. Waterfall plots show how the output of the headphones decays from a steady state. Imagine a wide‑bandwidth noise signal is instantly switched off; the waterfall shows how quickly the headphone output decays across the 20Hz to 20kHz audio band. The ‘floor’ of the waterfall in Diagram 3 and Diagram 4 is ‑25dB and the total time period, running from the back to the front, is 20ms. In the case of the open‑back DT 900 Pro X, the output falls almost instantaneously across most of the band except for the region around the driver’s fundamental resonance (which also corresponds to the peak in the impedance curve). The DT 700 Pro X behaves in similar fashion above 1kHz and around its fundamental resonance, but shows an additional region of slower energy decay, from around 100Hz to 500Hz. Again, this region of slower decay is I think likely to be the result of the closed‑back architecture.

Diagram 4: A waterfall plot of the DT 700 Pro X.

Listening In

Measuring is one thing, but actually using the headphones is a different game entirely. To begin with, I should mention comfort. In spite of their extra weight compared to the Sennheiser HD 400 Pro, I found both the Beyerdynamic models perfectly comfortable. The weight is noticeable, but for my money it’s by no means a deal‑breaker, or even a problem. The sturdy build, generous earcup diameter and soft velour feel of the DT 900 Pro X and DT 700 X also endows them with a cosy, cosseting feel, but without too strong a head‑clamping force. Furthermore, as a wearer of reading glasses when I’m at my DAW screen, I’ve found myself struggling in the past with headphones, like the Sennheiser HD 400 Pro, which have elongated, elliptical earcups and higher head‑clamping force. They tend to clamp the arms of my glasses frame against the side of my head which, after a while, results in discomfort. I had no such trouble with the DT 900 Pro X and DT 700 Pro X.

So the DT 900 Pro X and DT 700 Pro X are comfortable on the head and ears, but what of their sound? Cutting to the chase, they’re both really excellent. First, however, it was interesting to compare and contrast the open‑back DT 900 Pro X with its Sennheiser HD 400 Pro competition. I’d call the result a dead heat. They are both fine headphones that produce the kind of naturally balanced, open sound, free of quirks and colorations, that’s vital if they’re to be used for serious audio production work. The DT 900 Pro X is noticeably more sensitive than the Sennheiser HD 400 Pro X and to my ears is balanced very slightly warmer (comparing their measured frequency response curves would suggest so too), but it is a relatively minor difference and, with their levels equalised, I was actually struck more by their similarities than their differences. I spent a few enjoyable and interesting hours comparing the DT 900 Pro X and HD 400 Pro by surfing through Apple Spatial material on Apple Music and could genuinely not choose a preference between them. Listening to the Apple Spatial material became far more interesting than trying to work out which was the better headphone!

They are both fine headphones that produce the kind of naturally balanced open sound, free of quirks and colorations, that’s vital if they’re to be used for serious audio production work.

Moving from the open‑back DT 900 Pro X to the closed‑back DT 700 Pro X is a similarly enlightening experience. The DT 700 Pro X is also undoubtedly a very capable headphone. It displays fundamentally a similar set of characteristics and level of performance to the DT 900 Pro X, but it does reveal its closed‑back nature through a marginally less expansive and natural tonal balance than the DT 900 Pro X. To my ears it has a slight bloom in the low midrange that’s not present on the DT 900 Pro X. In a recording or mix context this might make subjective judgement of tonal character marginally more tricky, as it throws a little doubt into the equation over what’s inherent to the material and what’s a headphone artefact. But of course, on the other hand, the DT 700 Pro X comes with the acoustic isolation and lack of leakage that the DT 900 Pro X fundamentally can’t offer. In the end, all I’m really doing is describing the fundamental trade‑off between two very good open‑back and closed‑back headphones.

When I first opened the DT 900 Pro X and DT 700 Pro X packaging and realised that they are so much heavier than the Sennheiser HD 400 Pro, I was concerned that they might be struggling to compete. I needn’t have worried. In the end, the extra weight really didn’t bother me, and in fact I came to appreciate the Beyer models’ more sturdy and somehow less plasticky construction. I also came to appreciate the sound of both models enormously — they are both impressively capable. If I were mixing or mastering using headphones and had a choice of either the Sennheiser HD 400 Pro or the Beyerdynamic DT 900 Pro X, I’d consider myself very much sorted on the headphone front. And if I were tracking and needed a really capable pair of closed‑back headphones, I’d be similarly delighted and confident if I could reach for a pair of Beyerdynamic DT 700 Pro X. Both the DT 900 Pro X and DT 700 Pro X are really excellent headphones.