Sennheiser HD 660S Repair

The Sennheiser HD 660S are over-ear open-back professional headphones, released in 2017, and are the successor to the Sennheiser HD 660.

The HD 660S are balanced headphones, with Sennheiser's detachable two-pin connector, with support for a non-balanced connections. The headphones has 42 mm ventilated drivers, with 150 ohm transducers and aluminum voice coils.

The HD 660S has a studio tuned frequency response, reproducing down to 9 Hz and up to 41.5 kHz. The 660S and are slightly darker tuned compared to its predecessor the Sennheiser HD 660. The 660S has a rolled of sub-bass below 100 Hz, which is normal for open-back headphones, and a slightly under-empathized mid-range.

Model number	Brand name
The model number is printed on the outside of the headband.	The Sennheiser wordmark is printed on left top side of the headband.

Model number: 508826

Release date: 2017

Drivers:

• Size: 42 mm
• Sensitivity: 104 dB SPL/V
• Impedance: 150 ohm
• Frequency: 9 Hz - 41.5 kHz
• Maximum input power: 500 mW

Body:

• Type: Over-ear
• Enclosure: Open
• Weight: 260 g

Interface:

• Socket: 2-pin connector

• Sennheiser: HD 660S Official Product Page (archived 02/2026)