Sennheiser HiRes Audiophile Headphone (HD 660 S)

Product Information

If you carefully listen to fast electronic music on the HD 650 or HD 600, you can hear a micro-echo, like an unpleasant resonance, maybe and effect of the over-damping behind the diaphragm (again just a guess). This effect damages the delimitation of notes and each individual sound end up not being sufficiently well defined. The mid-bass clearly stands out and always attracts attention on itself, continuously screaming “look a me!”. As expected from an HD 600-series Sennheiser, the mids on the HD 660S are simply spectacular. In terms of frequency response, they are simply perfect to my taste. The upper midrange on the HD 6XX and HD 58X came across as a little forward or shouty, as they had a little extra energy at around 3k-3.5k, but this was not the case at all for me on the HD 660S; I found its upper midrange to be very smooth. The timbre on this headphone’s mids is–again, like the other headphones in the series–spot on and very natural sounding. For detail retrieval and resolution in the midrange, I thought that these performed great as well. From my listening, I personally found them to be an upgrade over its predecessors as well as a little more resolving than the LCD-1, Sundara and DT 1990 Pro in the mids.

The HD 660 S features a new transducer design developed by Sennheiser. This results in improved control of the diaphragm movements thanks to a specially manufactured precision stainless steel fabric, which is adapted to the contour of the diaphragm. Extremely light aluminum voice coils ensure the highest impulse fidelity. While both previous iterations of theHD 660 are regarded as modern classics amongst Hi-Fi heads, the need for a tweaked version of what many feel was aural perfection shows what a discerning bunch audiophiles are. The only problems with them is that the clamping force on the head is a little too strong, and they can sound a little "veiled" or distant in the lower presence region around 800Hz to 1500Hz—the HD 650 a bit more so than the HD600. Some will say the HD 650 has more mid-bass bloom, which it does, but it amounts to the same thing relatively speaking. So again I’ll state that the “handshake” given to me from Sennheiser was firm and filled with confidence, which is exactly what I’ve come to expect from Sennheiser.

Sennheiser revives a classic design and this is one of those rare moments where some people will prefer the remake to the original

How close is the guitar with the 660S! It's exciting but there's less sense of distance of the stage. Nevertheless, the timbre of the strings are exciting, albeit slightly resonant on the lower end, while the 600 has a more "acid" sound. The reverb of the recording venue is more evident in the 660s. The comfortable soundstage and detailed imaging hasn’t changed much. This was kinda difficult to determine because the forwardness of the mids and upper bass makes the soundstage sound a bit closer than the original HD650 did but when playing normal classical/instrumental music, at least me personally, I can’t hear a notable difference between the two in the soundstage and detail side of things.

The way the HD 606S2 handle the midrange and voices is a real highlight. Vocals sound super-smooth and ooze refinement. Play A-Ha’s MTV Unplugged version of Take On Me at 24-bit/94kHz and the Sennheisers paint a beautifully intimate picture. Morten Harket’s smooth tone is both captivating yet gentle with it. The accompanying instruments such as the guitar and piano are extra ingredients that add to this soothing rendition. Like I told you, the HD 660 S is only 2dB more sensitive than the HD 650 and HD 600, so the halved impedance has very little impact on this.Sennheiser HD660S + Burson Play - Burson Play is a great little device created by Burson, a rather loved and well-known company. Play is most an Audiophile-Grade, modular, integrable DAC/AMP for desktop, and especially for desktop PCs. Its power is quite fit for HD660S, and it is a good way to prove that HD660S can sound pretty sweet on a proper desktop-class setup. The beauty of Burson Play comes from the fact that you can integrate it in your PC setup, so you can plug HD660S, or any other audiophile-grade headphone, directly in your battle station, and just enjoy audiophile-grade sound without having more devices on your desk or table. The sonic performance is quite variable with Burson Play, as it allows the user to change its OP-AMPs, but the most basic configuration offers a warm and smooth sound, with a pretty good soundstage, which pairs well with HD660S. For the HD660 S2, Sennheiser revised the coil of the S2, and it now matches the 300-ohm impedance of the legendary HD 600 & HD 650. This new coil also provides higher magnetic force and electrical dampening for cleaner impulse response. The surround – according to Sennheiser – is now more compliant too, dropping the resonant frequency to 70 Hz . Considerable effort also went into optimizing the airflow around the transducer. There’s more sensitivity over the entire frequency spectrum because the magnet´s air gap works more efficiently now. Taken together, these measures result in even greater precision, speed, and resolution — with double the sound pressure at the lowest frequencies.