The £430 over-ear, open-back design build on their HD 650 predecessors with a new transducer and lower impedance.

The HD 660 S don’t look a million miles away from the HD 650s - despite wearing a new matt-black finish, they still feature their predecessor’s elliptical ear cups, thickly cushioned headband and replaceable ear pads. But Sennheiser has worked on the innards in the attempt to take performance to the next level.

According to Sennheiser, the new transducer offers improved control of diaphragm movements, with the improved acoustic design aiming to minimise distortion.

With 150-ohm impedance, the HD 660 S are also determined to be just as easily used with smartphones and portable music players as with hi-fi components (although we aren’t sure the open-back design lends itself to the former in any case).

Whether they’ll take the fight to the Shure SRH1540s (£430) – Award-winners at this sort of price – is yet to be established. But a mid-October release date means we should be able to find out very soon.


More after the break

Sennheiser IE 800 S are latest version of What Hi-Fi? Award-winners

12 of the best over-ear headphones

14 brilliant pairs of headphones comprise What Hi-Fi? Awards 2017 winners

11 of the world's most expensive headphones

Over-ear (yet in-ear) Nuraphones promise tailored listening 

Libratone launches Google-certified USB-C and wireless headphones