The Sennheiser HD 800 S outperforms the HD 660S2 in soundstage width and treble extension according to Audio Science Review and RTINGS data, but the HD 660S2 provides comparable midrange at roughly half the price. The HD 800 S weighs 70 g more and costs significantly more, making it the choice for dedicated listening rooms. Both share 300 Ω impedance requiring amplification.