Наушники — Sennheiser HD 660 S2

The HD 660 S2 is an open-back dynamic headphone from Sennheiser, introduced in early 2023 as the successor to the HD 660S. The main change is the transducer impedance, which rose from 150 ohms on the original to 300 ohms on the S2, together with revised airflow around the driver. It is made in Ireland and lists at USD 679.95 with a two-year warranty. Cosmetic changes include bronze instead of silver lettering on the cups.

Key specs that matter

A 38 mm transducer with an ultra-light aluminium voice coil sits in each earcup. The frequency response is quoted as 8 Hz to 41,500 Hz, one hertz lower at the bottom than the 9 Hz of the HD 660S. The sound pressure level is 104 dB at 1 kHz and 1 Vrms, and total harmonic distortion stays below 0.04% at 1 kHz and 100 dB. The headphone weighs 260 g, and the magnetic field is listed at 4.5 mT. Two 1.8 m cables are supplied - one with a 6.3 mm plug and one with a balanced 4.4 mm plug - plus a 6.3 mm to 3.5 mm adapter and a soft carry pouch, which replaces the hard case of the earlier model.

Engineering and use context

Sennheiser fits what it calls a vented magnet system, designed to reduce distortion by letting air escape from behind the voice coil instead of building up pressure. The surround holding the diaphragm was made more compliant for the S2, dropping the resonant frequency of the driver to 70 Hz, which extends its output in the lowest octaves. Engineers also worked on the airflow around the whole transducer assembly, and this raised sensitivity compared with the HD 660S. The aluminium voice coil keeps moving mass low. The cables supplied with the S2 are significantly shorter than those of its predecessor, which suits desk use. Velour earpads enclose the ear, and the open back means the headphone leaks noise to people nearby.

Pairing

With its high impedance and sensitivity the HD 660 S2 draws little current but needs a reasonable voltage swing, so desktop headphone amplifiers and DACs with a proper headphone output are the natural partners. The balanced Pentaconn cable connects directly to balanced portable players and desktop amplifiers that use that socket, while the single-ended cable covers single-ended amplifiers and integrated amplifiers with a front headphone jack.

Alternatives

The Sennheiser HD 650 is the older open-back model in the range, with a 42 mm transducer and a single 3 m cable at USD 579.95.