Superlux HD660 Pro

Reduction to the essentials

The Superlux HD660 Pro package is straightforward. In addition to the headphones themselves, all that’s included is a gold-plated screw adapter that allows the mini-jack plug cable to be used on 6.35mm jack sockets.

OK, let’s be honest: The name HD660 Pro will be familiar to many headphone fans. But Superlux don’t stop with just the HD660 Pro’s almost identical name. The design of these headphones is reminiscent of those other circumaural, closed classics in terms of the ear cushions, the ear cup arms, the exposed cables, the headband design and the single-sided, permanently-installed supply line. At first glance, the design of the Superlux headphones seems familiar to the observer, and this need not be a bad thing.

Ultra-wide frequency response

The HD660 Pro use dynamically driven drivers with powerful neodymium magnets, which according to the manufacturer cover an audio transmission range from 10 Hz to 30 kHz. This frequency range is wider than the audio range typically audible to humans. It will therefore be exciting to hear to what extent these headphones can reproduce ultra-deep bass easily and how open their sound image comes across in the trebles. The average impedance we measured was just under 137 Ohms, making these headphones particularly suitable for professional and hi-fi preamps. On the other hand, weaker preamplifiers such as those used in mobile devices lose some of their playback volume. In general, the maximum sound pressure level of the headphones is not too high at 95.4 dB SPL.

Wide, soft and warm

The Superlux headphones have a fixed, non-removable cable with a comfortable length of 2.3 metres. This makes the headphones suitable for a variety of studio situations. Whether the HD660 Pro is used by an instrumentalist for monitoring during recording, or the sound mixer is set up in the studio and rolling back and forth with an executive chair … the cable length provides freedom of movement to the headphone preamp.

Together with the cable, the headphones weigh 322 grams, with the headphones themselves weighing 287 grams. For a pair of headphones of this size they are therefore a relatively light model. Accordingly, the contact pressure does not have to be as great to keep these cans on your ears. And this is exactly what happens. The fit of the headphones is excellent. The size adjustment of the headband is ratched so that the headphones retain their setting even after they are taken off. The ear cushions are made of velour and to a certain extent, they are breathable. Minimal sweating cannot be avoided, especially if the room temperature is warm. In any case, the surface is soft and feels good on the skin. The headband padding is surrounded by an artificial leather that also tends to sweat a little under the conditions already mentioned. However, this padding is also soft and cushions the headband well.

Audio smoothie

The first thing I noticed about these headphones was that the sound of was brilliant and detailed. The sound is present and open in the trebles up to the super high frequency range. This benefits not only the subjective signal resolution but also the stereo impression and the depth staggering. At the same time, the trebles are not obtrusive. In the sibilants, however, a certain sharpness here and there cannot be ignored. These headphones are also powerful at the other end of the spectrum. Basses are reproduced right down to the low bass range without being exuberant. I didn’t find any disturbing resonances, which can occur with some closed headphones. The mids are surprisingly soft and complement the frequency ends in a velvety fashion. You can even listen to guitar-heavy music at a permanently loud volume with this device.

Superlux describe the sound of the HD660 Pro as natural and well balanced, and my test confirmed this. Due to their wide frequency response, the HD660 Pro are attractive as mixing headphones. In addition, the acoustic insulation to the outside is OK and the damping of outside noise is OK, too. This also makes the Superlux HD660 Pro suitable for recording and monitoring use in the studio. The reproduced dynamics are also good. Transients in particular are reproduced with punch. Very low playback volume has no negative effect on the listening impression. These Superlux headphones, with their frequency distribution and closed design, did not appear significantly quieter than other test candidates.