Beyerdynamic DT 1770 PRO and Sennheiser HD 660S2 offer different noise cancellation capabilities (NA vs AMBIENT), which can impact how effectively they block external noise. The driver size differs between the two (45 mm vs 38 mm), which can influence sound depth, bass response, and overall audio clarity. The frequency response differs (5 Hz - 40000 Hz vs 8 Hz -41500 Hz), which can influence how well the headphones reproduce lows, mids, and highs. From a usability standpoint, both models provide a reliable and premium headphone experience. If you're comparing Beyerdynamic DT 1770 PRO and Sennheiser HD 660S2, both models offer a strong combination of sound performance, comfort, and modern wireless features. Impedance levels vary (250 Ohms vs 300 ohm), which can affect compatibility and audio output when used with different devices. Both models support modern Bluetooth connectivity, ensuring stable wireless performance with compatible devices. There is a noticeable difference in weight (388 g vs 260 Gm), which may affect comfort during extended use. Both headphones offer solid battery performance, making them suitable for long listening sessions and travel.

Verdict: Both models are competitive, and your decision should be based on your usage needs and preferred features.