Sennheiser HD 660s

The reviewer compares the Sennheiser HD 660s to the Hifiman Sundara and concludes that the Sundara is the better choice due to its superior bass extension, soundstage, and resolution, despite the HD 660s having good build quality and imaging. The HD 660s is seen as overpriced given the existence of the cheaper HD 6xx, and its soundstage is notably narrow. The reviewer recommends the Sundara for most users, though notes the HD 660s may pair better with certain high-end tube amplifiers.

The reviewer finds the HD 660S to be an excellent headphone with superior detail retrieval and a slightly wider soundstage compared to the HD 600/650 line, and notes it is easier to drive. However, he argues that the premium price is hard to justify given the modest performance gain over cheaper alternatives like the HD 580, making it a great but not necessarily cost-effective choice.

The reviewer finds the HD 660s to be his favorite in the HD 600 series, praising its smooth midrange, good resolution, and improved imaging over predecessors. However, he criticizes the lack of sub-bass, a narrow soundstage, and a peak at 5.5 kHz that adds a slightly boxy tone. He ultimately struggles to recommend it at its $499 MSRP due to strong competition from cheaper alternatives like the HD 6XX, suggesting it's only competitive when discounted.

The reviewer praises the HD 660S for its accurate and dynamic bass, lush and precise mids, and non-fatiguing treble, along with a wide soundstage and detailed imaging. They highlight the comfortable build and note that pairing with a tube amplifier can further enhance clarity. The headphones are recommended for studio professionals, gamers, and critical listeners.