https://en-us.sennheiser.com/headphones-audiophile-high-end-hd-660-s Price: $499.95 USD Technical Data Impedance - 150 Ω Connector - Stereo jack plug, gold-plated 6.35 mm, unbalanced, 3-pin 4.4 mm, balanced, 5-pin Frequency response - 10 – 41,000 Hz (-10 dB) Sound pressure level (SPL) - 104 dB at 1V 1kHz Ear coupling - Over-ear (circumaural) THD + N, total harmonic distortion and noise - < 0,04% (1 kHz, 100 dB) Transducer principle (headphones) - Dynamic, open Weight w/o cable - Approx. 260 g (without cable) A new audiophile versatility The new HD 660 S lets you enjoy sophisticated audiophile sound in even more listening situations. The successor of the legendary HD 650 excels with the improved performance of its new transducer design. Thanks to its lower impedance, it delivers reference-class sound also when connected to hi-res mobile players, thus offering much greater versatility. The HD 660 S is an elegantly designed piece of high-quality engineering that indulges the demanding listener with aural precision and great wearing comfort. Sound for the passionate music enthusiast Made for the demanding listener, the HD 660 S surpasses the exceptional performance of its predecessor, the legendary HD 650. With a crisp bass, excellent mid-frequency response, and a gentle, pleasantly natural treble, the HD 660 S has an expressiveness that immerses you in every emotion and nuance of music. Still, it always stays exceptionally accurate and transparent. Cutting-edge Sennheiser technology The HD 660 S features a new transducer design developed by Sennheiser. This results in improved control of the diaphragm movements thanks to a specially manufactured precision stainless steel fabric, which is adapted to the contour of the diaphragm. Extremely light aluminum voice coils ensure the highest impulse fidelity. The transducers are carefully selected and paired by hand to ensure consistently narrow (±1 dB) tolerances. Supreme connectivity The HD 660 S has been created to enjoy music in supreme quality and from many different audio sources. Thanks to its low impedance it also offers reference-class fidelity with hi-res mobile players. Naturally, the HD 660 S reveals its full potential when it is connected to the balanced outputs of a dedicated headphone amplifier such as the HDV 820 or to the balanced output of a mobile digital audio player. Accordingly, it comes with a choice of cables for just about any occasion. All cables are made of highly conductive OFC copper, featuring very low handling noise and sturdy para-aramid reinforcement. Designed for high-end comfort Everything about the HD 660 S makes listening a pure pleasure – not least its strong yet lightweight open construction. The elliptical ear cups are shaped to follow the anatomy of the ear, while thick padding on the headband and the replaceable ear cushions guarantee hours and hours of listening in supreme comfort.