Beyerdynamic DT 990 PRO

When my friend Charles asked me to digitise his record collection for him — the remaining pieces he had salvaged from the flooding in his basement — I needed a pair of headphones to oversee the process with. My last use of headphones had been so long ago that I could not remember who I had lent my Sennheiser HD580s to. Nor could I be sure that I still had them, considering they were from 1995. (I had originally written 2008, but this was not true.)

I contacted Jens, who is a composer and producer of music himself and usually quite knowledgeable about what is available on the professional studio market, to ask him for advice concerning reasonable headphones for my task. He mentioned that he was quite happy with his AKG K271 MK2 headphones. Jens referred to them as being “honest and revealing”. If I wanted even more honesty, he suggested, I might also consider the open K702. I thanked him for his prompt and knowledgeable support and bought the Beyerdynamic DT 990 PRO instead.

Do you have such moments, in which you know that you are getting excellent advice and then end up doing the exact opposite? In retrospect, I think it was the AKG headphone’s bulky look that put me off purchasing them. The two solid steel rods connecting the two ear pieces that remained fixed while only the head strap was lowered. This part was designed so much more elegantly on the Beyerdynamics and made me blind to some obvious disadvantages that should have got me thinking, especially with my prior knowledge in audiophile matters.

For one thing, the Beyerdynamic DT 990 PRO only had one single, non-detachable signal cord. A single cord had some disadvantages, when it came to signal integrity, because the two channels ran in very close proximity to each other over a longer distance. This could potentially cause inductivity that negatively affected the signal. The cable being curled like an old telephone cord only contributed to this phenomenon. In HiFi, cables touching cables was generally not a good idea and to be avoided.

I also could not help but wonder, if the two channels had cables of the exact same length, as one of them needed to be run over to the other side of the headphone to reach the other driver. The relatively poor center image of the 990 PRO, especially in comparison with the T1 of the same company, made me doubt that this was the case. One could argue that this should not have mattered on a short cable run such as this. But, if this had been the case, why did Beyerdynamic not simply use the same unequal cable design on their flagship T1 headphones? The answer was simple: Because in HiFi everything mattered.

The fact that the cable was not detachable could be seen in two ways: On the positive side, a soldered connection did not inject as much mass into the signal path as a plug would have done. But on the negative side, it meant that I was stuck with the cable it came with, even though I did not like it much. No upgrade was possible in this case, unless I was prepared to take out my soldering iron and get busy soldering new connections.

The DT 990 PRO were of light weight and did not press too firmly on the temples. I could see that wearing them for many hours would not present a problem. I did find that they could get warm with time and would not recommend them in areas of high humidity or temperature. However, all this I could have easily lived with, if they had offered greater tonal balance. This was the most obvious weak point of the DT 990 PRO headphones and made them rather undesirable for audiophile listeners. It was sometimes said that they were non-linear or ‘HiFi’-sounding — whatever that meant — but I do feel this to be an understatement.

Some frequencies of the mid-band strangely seemed suppressed, either by the driver or cabinet design, or by the thick acoustic foam-padding over the drivers, as to make voices sound thinner and sharper. I tested this with three different kinds of output: my computer sound card (only when digitizing records), our Denon CD player’s internal headphone amp (for comparison), and our Douk Audio T-3 Plus tube headphone amp (during an audition). The loss in frequencies remained similar, and this, although the treble was the harshest on our T-3. Since the latter had no difficulties driving high-resistance headphones and worked very well with the Beyerdynamic T1, I assumed that the effect of a recessed mid-band was built into the headphones themselves.

Given my narrow range of amplifier equipment, it was well possible that the DT 990 PRO would have performed better in combination with other devices. However, especially having the T1 as benchmark, I find it hard to believe that any differences in source design could paste over the general tendency of the DT 990 PRO to sound unbalanced, especially on vocals.

Specifications:

• Driver Type:  single, dynamic
• Design:  over-ear, open
• Frequency range:  5 - 35.000 Hz
• Nominal impedance:  250 Ohms
• Sensitivity:  96 dB (1 mWatt, 500 Hz)
• Harmonic distortion:  0,2% (1 mWatt, 500 Hz)
• Power rating:  100 mWatts, max.
• Cable:  Single (spiralled), fixed
• Plugs: 3.5mm + 6.3mm jack
• Place of manufacture:  Germany
• Year:  2021

View full-size image