Sennheiser HiRes Audiophile Headphone (HD 660 S)

Product Information

I did some pad rolling with Dekoni’s selection of Elite pads for the HD600 series, and can offer a strong recommendation for hybrid pads for those looking to fill out the bass a little bit.

On the flip side, I found the 660s to be slightly – and I emphasize slightly – more forgiving with entry-level gear than either 6XX or DT880. The original Sennheiser HD600 was released in 1997, and much of what the brand has done since has been a refinement and improvement of that monumental flagship headphone. The neutral presentation of vocals, guitars, and drums prove that the HD 660S2 is still a recording-studio-worthy headphone.

The planar magnetic HiFiMan Sundara 2018 are better critical listening headphones than the Sennheiser HD 660 S. Silly, I know, but I think a stealth black look helps put the focus on where it belongs: sound quality, not looks. Right away I will say that these are my favorite headphones in Sennheiser’s line-up, and for the music that I listen to the most (classic rock), I really, really enjoy them.

I personally found them to have plenty of volume on most devices I tested, like my MacBook Air and Nintendo Switch.On its product page, Sennheiser claims 104dB/Volt for the HD 660 S; in its manual, Sennheiser say the HD 650 has 103dB/Volt sensitivity. Mid-bass, responsible for the body of bass guitars and punch of kick drums, follows well our neutral target. There’s enough clarity to separate the rolling waves of guitar distortion and clattering drums, and even the brash, overdriven drum and bass of Current Value’s Bigger Picture manages to bounce along excitedly without ever veering too far into harshness.

The HD 660S was launched with a special video and unlike you’d expect it doesn’t feature the typical marketing talk. The GD graph also shows that the entire group delay response is below the audibility threshold and the spikes under 20Hz won’t be audible. Although I have yet to try a pair of open-back Sennheiser ‘phones I’ve heard nothing but good things about them. We also see a change in impedance: the HD 660S2 comes in at 300 ohms, while the impedance of the S1 is 150 ohms. The timbre on this headphone’s mids is–again, like the other headphones in the series–spot on and very natural sounding.

The midbass delivers enough punch to prevent HD660S from feeling “bass lite,” but hip-hop and electronic music in particular will feel a little empty without the low end extension. However, the carrying pouch ultimately seems a little more appropriate for a headphone like the 660; as I’ve already mentioned, the 660S/S2 are closer to being a high quality everyday-use pair of headphones than an ultra-premium pair to be locked away in a protective case.