Sennheiser HD 660S2 Wired Audiophile Headphones - Natural Open-Back

Our review of the Sennheiser HD 660S2 finds a pair of wired, over-ear headphones aimed squarely at listeners who prioritize natural, high-fidelity sound and extended comfort. The single biggest reason to consider them is the open-back design paired with 42mm transducers and an ultra-light aluminum voice coil, which deliver a spacious soundstage and exceptionally clear highs while still providing deep, controlled sub-bass that makes acoustic and orchestral music feel immediate and alive.

Key Features

• Audiophile open-back sound: The open-back design creates a wide, natural soundstage that helps complex mixes breathe and instruments sit in a realistic space.
• 42mm transducers with aluminum voice coil: These drivers provide detailed highs and rich mids while keeping distortion low at moderate listening levels.
• Deep controlled sub-bass: Frequency response reaching down to 27.5 Hz gives weight and clarity to low piano notes and bass drums without becoming boomy.
• Comfort for long sessions: Breathable, plush ear cushions and an over-the-head fit reduce fatigue during extended listening or monitoring sessions.
• Detachable wired cable: Removable long cables add convenience for desktop systems and audio interfaces while keeping the headphones simple and reliable.
• Premium construction: Build quality from Germany and Ireland focuses on durable materials and an understated, elegant finish.

Who It's For

The HD 660S2 is best for audiophiles, home listeners, and music professionals who want an open, natural presentation for critical listening, mixing, and desktop enjoyment. Its clear mids and precise highs suit acoustic, classical, and vocal-forward material particularly well.

Those who need noise isolation, a closed-back profile for portable use, or wireless convenience should look elsewhere, since the open-back wired design prioritizes soundstage and air over isolation and on-the-go practicality.

Pros & Cons

Pros

• Exceptional clarity and natural presentation that reveal fine musical detail.
• Comfortable plush ear cushions that support long listening sessions without fatigue.
• Powerful yet controlled low-end reach that handles notes down to 27.5 Hz with precision.
• Detachable cable and solid construction for longevity and flexible use at a desk or with audio equipment.

Cons

• Open-back design offers little isolation and is unsuitable for noisy environments or portable use.
• Some buyers may find the value proposition mixed compared with other models in the same price area.

Specifications

Design	Open-back, over-ear
Transducers	42 mm with ultra-light aluminum voice coil
Low frequency response	Down to 27.5 Hz
High frequency response	Up to 4560 Hz
Cable	Detachable wired cable(s)
Comfort	Breathable plush ear cushions
Manufacturing	Crafted in Germany and Ireland

Our Verdict

The Sennheiser HD 660S2 is a refined wired headphone for listeners who value an open, natural soundstage, detailed highs, and a controlled low end. Its comfort and build quality make it a strong choice for home audiophiles and professionals working at a desk, and it represents good value for anyone prioritizing clarity and musicality over isolation or wireless features.

Frequently Asked Questions

Are these headphones closed or open-back?
They are open-back, designed to deliver a spacious soundstage rather than isolate from outside noise.

Can I use these with a phone or portable player?
Yes, but they are wired and perform best with a quality source or headphone amplifier; they do not provide passive isolation for noisy environments.

Are they comfortable for long sessions?
Yes, the breathable plush ear cushions and over-head fit are intended for fatigueless listening during extended sessions.