Dive deeper into legendary sound. Let’s meet the HD 660S2
Feb 7, 2023 at 7:13 PM Thread Starter Post #1 of 181
Feb 10, 2010
Hannover, Germany

Hello Head-Fi!

It sure is hard to keep a secret! We’re here to officially debut the HD 660S2, the latest in our 600 series of audiophile headphones. This dynamic, open-back set of cans brings a new flavor to this award-winning and best-selling family thanks to the feedback from you, the hi-fi community. We listened with a smile so that you could too – the HD 660S2 features a revised tuning that pulls you right into the action with just the right amount of sparkle to extract the best of your favorite tracks. Let’s take a closer look.

We're just getting warmed up

The established house “600 series” sound has stood the test of time, and continues to be a benchmark for not just evaluating music, but other gear too. Make no mistake, the HD 660S2 continues this family’s heritage for smooth and clear instrumentation, accurate spatial placement, and microscope-like detail retrieval…with a voicing supercharged for today’s sonic tastes. Those familiar with the 600 line will notice warmer, deeper bass and effortless treble that retains its silky heritage, bringing the listener closer to the emotion of the music. Those new to the series can expect a confident balance between reference and fun that is neither fatiguing nor passive. Let’s look at the frequency response and compare it to the HD 660S that it replaces:


Dynamic duo

Each transducer is extensively tested and measured, then matched at our Ireland production facility for a stereo pair that sounds identical to other HD 660S2s around the globe, unit after unit. Yes, the transducer is a large part of the story, but not 100% of it. The ventilated magnet design powering it has been proven to keep audio reproduction clean and it makes another appearance here. Airflow has been optimized even further compared to the first generation 660S, reducing the audible artifacts caused by turbulence around the diaphragm.

The voice coil is lighter than before and thus more responsive too, with an impedance of 300 ohms and a 10% weight loss. The result is a black backdrop for the nuances in your music to jump off of, and smoother treble response with noticeable transient clarity. On the opposite end of the frequency spectrum, sub bass response virtually doubles in measurement without sacrificing the definition needed to decipher complex musical passages. Improvements aside, the HD 660S2 pulls the speedy, punchy capabilities of its predecessor into the modern era to offer both presence and profile of thunderous kick drums, rumbling bass lines, and sensational sound effects. Even the transducer surround has been tuned down to a resonant frequency of 70 Hz, creating a complementary environment for bass waves to expand.


Wired up

The HD 660S2 is ready to connect to today’s best desktop hi-fi gear, shipping with two 1.8m (5.9 feet) cables–a 6.3mm (¼-inch) single-ended stereo plug cable and balanced, 4.4mm plug-terminated cable. Each is para-aramid reinforced for durability over the life of your passion for music. A 3.5mm (⅛-inch) adapter with strain relief lead is also included–it all fits inside the cinched storage pouch for safe keeping.

HD 660S2 features:

  • Intimate sound with warm, deep sub-bass reproduction
  • 38mm (diaphragm; 42mm overall) dynamic transducers matched to ultra-tight tolerances
  • 300 Ω impedance and ultra-light voice coil for outstanding detail retrieval
  • Open-back design for rich, detailed imaging and a spacious stereo field
  • Retuned transducer surround (70 Hz) for the ideal balance of impact and clarity
  • Ultra-fine steel acoustic mesh baffle and ventilated magnet negate turbulence around the transducer
  • Plush, velour ear padding and adjustable headband for long listening sessions
  • 8 Hz - 41,500 Hz frequency response
  • Includes two cables; 1.8m single-ended cable with 6.3mm plug, and a 1.8m balanced with 4.4mm plug
  • Includes 6.3mm to 3.5mm stereo plug adapter with strain relief
  • Total Harmonic Distortion: <0.04% (1 kHz at 100 dB)
  • 104 dB SPL sensitivity (@1 kHz / 1 Vrms)
  • Cinched storage pouch for low-profile storage and protection from dust
  • Crafted at our state of the art factory in Ireland

This new earphone will be available for pre-order and ships mid-winter, and will make a public debut at CanJam NYC - be certain to come by the Sennheiser stand and get a demo from @ericpalonen! While this is the official thread, there’s an ongoing discussion here, and a gear page for formal reviews. For more information including pricing visit our website or contact your local Sennheiser dealer. We are so quite excited for you to experience it, and will announce an HD 660S2 tour shortly.

Unofficial thread
Head Gear page
[Reserved for the tour]
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Feb 8, 2023 at 10:04 AM Post #4 of 181
As a happy hd660s owner, (thanks for the graphs) my first thought is "I can achieve that with a bit of EQ". If the rumours on price are correct, I suggest that Sennheiser reflect on the launch of the hd660s a little harder...
Feb 8, 2023 at 10:58 AM Post #6 of 181
This vs Meze 109 Pro would be an interesting comparison.
Feb 8, 2023 at 11:43 AM Post #10 of 181
Ngl half regretting selling my old 660s now just cause these seem harder to drive, the old 660s sounded great from my phone or digital piano, etc… I guess there’s the 560s and 58x but I don’t think they’re as good
Feb 8, 2023 at 12:03 PM Post #13 of 181
So if that graph is to be believed, how did they finally get actual low end into a 6–series headphone?
Feb 8, 2023 at 12:36 PM Post #14 of 181
Wow cool. Same SPL as the 660s so hopefully they’ll be just as easy to drive out of a smartphone.

I bought the 660s specifically because I wanted the ability to leave the desk with them and enjoy music on the couch or wherever I am.
You'll want an amp of some kind. The 660S2 is 300 ohms and to get the full experience it needs proper amplification.
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