Sennheiser HD660S2 new for 2023. Open back full size headphone, with improved acoustics added to the great traits of the 600 series - light weight, excellent comfort, long term reliability, replaceable pads and cable, appealing open soundstage and a great balanced clarity across the frequency range. The Sennheiser HD660S2 has subtle but formidable acoustic improvements - Sennheiser has improved the airiness in the top of the treble range and the sub bass response.
These two areas of the sound, the frequency extremes, are the most difficult to achieve alongside a balanced, clear midrange, so hats off to Sennheiser for improving a well loved product with no apparent downside.
The frequency chart shows the sub bass moved up relative to the mids by 4-6 dB - which will be heard as being correctly in balance with the rest of the frequency range, instead of fading as it used to be heard. 4-6 dB equals hearing the sub bass as up to double the strength as the prior 660s version. A very limited range of frequencies has been targeted so there will be no downside here - nice! The similar improvement in the top end of the treble will be heard as a more spacious, light and airy quality with the highest treble notes, bringing one of the most loved qualities of the HD800s down into the Sennheiser HD660S2, with a more delicate, airy treble. See below:
Impedance is up, at 300 ohms but these are still very sensitive and much easier to drive than the HD600. Cables have been shortened to 1.8m and a 4.4mm balanced cable is smartly included.
Sennheiser HD660S2 specs: