Sennheiser HD 660S2 front quarter over white background
Sennheiser HD 660S2 direct front over white background
Sennheiser HD 660S2 profile over white background
Sennheiser HD 660S2 drivers behind grill over white background
Sennheiser HD 660S2 grill with logo over white background
Sennheiser HD 660S2 product packaging over white background

Sennheiser HD 660S2 | Open-Back Dynamic Headphones

Regular price $599.95 Sale price$499.95 Save 17%


Sennheiser official black and white logo

Dive Deeper into Legendary Sound with the Sennheiser HD 660S2 Open-back

  • Open-Back, Dynamic, Over-ear Headphones with High Fidelity sound
  • Ultra-light aluminum voice coil with 300Ω impedance for excellent impulse response
  • Uniquely powerful vented magnet system for minimized distortion
  • Outstanding quality designed in Germany, made in Ireland
  • Intimate and precise yet non-fatiguing sound with great timbre and deep, accurate sub bass
  • Plush ear cushions and open design for maximum comfort

Bloom's Take

Some Sennheiser cans are in stores for decades. But the HD 660S2 follows closely on the heels of the original, offering the same frame with subtle updates to its look and sound.

The HD 660S2 opts for a smaller retail box with no fancy case and still provides 6.3mm and 4.4mm cables, albeit they are welcomingly shorter. Regarding sound, expect detail, clarity, and a natural timbre along with good air, and solid treble extension. Yep, that's largely true of its HD 600 brethren, but the S2 differentiates with deeper, more linear bass extension.

We feel that most of Sennheiser’s recent innovation hasn't come in massive changes but rather in incremental changes with subtle improvements over the predecessor. In the case of HD 660S2, the subtle tweaks to the tuning provide a clear improvement, crowning it the best sounding and performing HD600 series headphone Sennheiser has created thus far.

Read the full review here.

Sennheiser HD 660S2 headphones with Burson amplifier

Dive Deeper into your Music

Enjoy your music on a completely new level. An intimate, relaxed sound signature combines with outstanding precision and exceptional comfort — and now, extended sub bass — for a deeply moving experience. The extremely precise yet non-fatiguing sound of the HD 660S2 delivers even more impact with extended sub bass.

With an optimized surround, transducer airflow, and coil, our engineers doubled the sound pressure at the lowest octaves. You can feel the lowest note on the piano (27.5 Hz) or the kick of the bass drum (45-60 Hz) as if you were there.

The relaxed tone and open-back design make this extremely comfortable headphone great for long sessions. With warm tuning, smooth treble, and strong bass, the standard-setter for extended listening is now the standard-setter for extended bass as well.

Sennheiser HD 660S2 on Omega headphone stand with tube amp

Sub Bass Expands the Entire Sound

In doubling the sound pressure at the lowest frequencies, we’ve retained extraordinary precision and balance throughout the sub-bass, mid-bass, and beyond. Extension on the low-end changes everything by creating more space for the sound. Against a deeper backdrop, highs feel more brilliant, the soundstage deeper, and emotions stronger.

Improvement of a Legend

The revised coil of the HD 660S2 matches the 300Ω impedance of the legendary HD 600 and HD 650. This new coil also provides higher magnetic force and electrical dampening for cleaner impulse response.

The surround is also more compliant, dropping the resonant frequency from 110 Hz to 70Hz. All together, these measurements result in even greater precision, speed, and resolution with double the sound pressure at the lowest frequencies.

Detailed comparison of technical differences between HD 660S2 and HD 660S

Frequency Response Comparison

1. Between 20-200 Hz, the sound pressure level is significantly increased (twice the sound pressure at 20 Hz.) This results in a much better impact of percussion and electronic music, the most common user feedback.

2. Above 5000 Hz, overall, the response is stronger. This results in more perceived clarity.

3. Above 5000 Hz, the response is “smoother” (the difference between the louder peaks and quieter troughs is smaller.) So music reproduction is more natural, and fewer peaks mean less fatigue during long listening sessions.

Frequency sound graph of HD 660S2 compared to HD 660S

They Feel as Great as They Sound

The velour earpads of the HD 660S2 can only be described as a tactile pleasure. With just the right amount of tension for proper acoustic positioning and supple padding, the headband won’t draw attention away from your music. And with open-back design, the HD 660S2 gives your ears an extremely comfortable climate, even for super-long sessions. Low total weight and ergonomic headband rule out potential discomfort .The listening experience is as physically pleasing as the warm, non-fatiguing sound at its heart.


  • Transducer Principle: Dynamic, open
  • Transducer Size: 38mm
  • Frequency Response: 8 Hz - 41,500 Hz
  • Impedance: 300 Ω
  • Sound Pressure Level (SPL): 104 dB (1V)
  • Total Harmonic Distortion (THD): < 0.04% (1 kHz, 100dB)
  • Weight: 9.17 oz (260g)
  • Magnetic field: 2.5 mT
  • Sennheiser 2 Year Warranty

In the Box

  • Sennheiser HD 660S2 wired over-ear headphones
  • 5.9' (1.8m) cable with 6.3mm connector
  • 5.9' (1.8m) Balanced cable with 4.4mm Pentaconn
  • 6.3mm (F) to 3.5mm (M) adapter
  • Carry Pouch
  • User Manual

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Customer Reviews

Based on 1 review
Thomas Davis
I'm really enjoying these!

My introduction to higher end headphones came in late 1998 or early 1999 when I purchased the Sennheiser HD 600. I'm 62 years old now and probably don't hear as I did in my youth but I still love to listen to music. I've never considered myself an audiophile, but rather a music enthusiast who wants to listen on the very best gear that I can reasonably afford to buy. My original 600's wound up in the bottom of the dishwasher one night while I was away at work, entirely my fault as I left them where my nearly one year old son could get his meat hooks on them. I'm guessing they went into the dishwasher while my wife was multi-tasking in the kitchen. It didn't end well! I decided to temporarily replace them with a cheaper pai of headphones and never got around to replacing them until about six or seven years ago when I really kind of shifted to listening to desktop audio and getting more into headphones. My wife is more into the video stuff and my son is autistic and sensitive to noise, so headphones were especially logical. I currently own seventeen pairs of headphones and haven't purchased a Sennheiser in a very long time. So why return to the 600 series? Well, the original intent was to purchase the Audeze MM100, and I did. I had it paid off, but Audeze keeps delaying the release date and I got tired of waiting after three or four months. I saw these as an open box pair on SALE for $449 and jumped on them. I only have a few hours of listening to them but I personally love them. What you get here is the same build quality you know is going to last for decades, an updated aesthetic which I especially like with the copper accents and refined lines. You're getting a more FUN sounding pair of headphones, I think, with it's extended bass and less of that notorious Sennheiser veil. I think the top end is a little brighter than the 600, though not sibilant. The mid-range is still the star of the show and here I think the 660S2 is a bit wider in soundstage than the 600. At this point I have only heard these connected to my laptop using a Fiio BTR7 DAC/Headphone Amp and they sound outstanding. I'm not a guy who puts much stock in "burn-in" time but we'll see. What I'm really looking forward to is hearing them on tubes!

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