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Brand New Sennheiser HD660S2 300hm Headphones

Today, we will look at the brand-newSennheiser 660S2 headphones. This article will primarily discuss the headphones in terms of build quality, comfort, design, and sound quality, with some comparisons to my original 660S headphones. 

First, let’s talk about why Sennheiser is making these changes to what many users already felt was a very enjoyable set of headphones. Sennheiser took lots of feedback from their users of the 660S in making some changes to the 660S2.

Some of the feedback from users was directly related to the bass signature of the 660S and how it didn’t reach low enough in the FR. Many users also preferred the 300-ohm impedance of Sennheiser’s other headphones and desired a bit more detail retrieval.

Sennheiser listened and made some changes based on this feedback. The HD660S2 uses 42mm transducers with 38mm diaphragms capable of 8 Hz-41 kHz, an improvement over the HD660s in the low end. The 660S2 is now a 300-ohm headphone with a 104 dB efficiency compared to the 150-ohm 106 dB original 660S.

The THD of the 660S2 remains the same as the original 660S at .04%, along with the weight of the headphones, weighing 260 grams without the cable. In addition to these changes, Sennheiser reduced the coil weight by roughly 10%, which according to Sennheiser, increases the high-frequency amplitude and helps to improve detail retrieval.

Build and Design Quality

HD 660S2Some other key features, according to Sennheiser, of the 660S2, which is designed in Germany and manufactured in Ireland, is a powerful vented magnet system for minimized distortion, plush ear cushions, and open design for better comfort.

The revised coil of the HD660S2 matches the 300-ohm impedance of the legendary HD 600 and 650, now providing higher magnetic force and electrical dampening for cleaner impulse response.

Sennheiser states they significantly increased the compliance of the surround by dropping the resonance frequency from 110 Hz to 70 Hz. Ultimately sound pressure has doubled at the lowest octaves.

They also optimized airflow around the transducer by decreasing air leakage between the front and back of the transducer, which helps to better maintain pressure for low frequencies.

According to the measurements provided by Sennheiser, between 20-200 Hz, the sound pressure level is significantly increased, which according to Sennheiser, results in a much better impact of percussion instruments and electronic music, based on user feedback. I will discuss this more during the sound impressions portion of the article and how they compare to my pair of HD660S.

Above 5000 Hz overall, the response is stronger, which according to Sennheiser, was to improve the perceived clarity of the headphones while also smoothing the response between the louder peaks and quieter troughs, creating a more natural, less fatiguing sound.

Making some of these changes especially moving to the 300-ohm impedance, which decreased the voltage sensitivity of the headphones from the original 660S, which means that for the end user, a more capable amplifier for the best sound quality is highly recommended, just as it is with the 600 and 650 headphones.

The new 660S2 headphones include a 6.3mm cable, and a 4.4mm balanced pentacon cable, both 1.8 meters in length, a 6.3mm to 3.5mm adapter, and a soft carry pouch selling for $599.95. With many new technical changes covered, let me give you my subjective thoughts on the build quality differences before going into my sound impressions. For comfort, the clamping force has been reduced on the 660S2, and the headband also feels a little softer on the top of my head than the original 660S, two very welcome changes.

I also like the copper accents on the HD660S2 headphones vs. the silver found on the original HD660S. The more low-key branding on the 660S2’s headband is also a plus. I am pleased with the changes from a build quality perspective and feel the new headphones are better for my overall user experience.

Sound Impressions

 Now for my favorite part of the article, how does the 660S2 sound, especially when compared to the original 660S? 

For my sound impressions, I primarily listened with myChord Hugo TT2 for a reference premium solid-state headphone amplifier and DAC.

I also listened briefly out of the headphone outs on my Marantz 40n integrated and Michi X3 integrated. For tube amps, I listened to the McIntosh MHA200 and my Bottle Head Crack with Speedball fed by the Chord Hugo TT2 as the DAC to formulate my impressions.

I listened to music across several genres from several of my Tidal and Qobuz playlists and will share a few notes from my music-based impressions about the 660S2 and how it compares to the original 660S.

One of the first things I noticed about the new 660S2 is a tighter, punchier, more dynamic sound than the OG 660S, with better separation from the bass regions to the mid-range. This allows for better instrument separation, layering, and better-defined vocal presentation.

The overall signature sounds more balanced and effortless in presenting music. The bass sounds better extended and more defined than the 660S. In addition, the soundstage imaging and spacing are improved.

The soundstage is still intimate sounding with mostly a left-to-right presentation; however, it is an improvement over the original 660S, and when comparing the two headphones on

Friend of the Devil from the Grateful Dead, the original 660 sounds a bit congested between all the vocals and instruments compared to the new 660S2.

There sounds to be a bit more energy in the treble from the 660S2 allowing for a good balance between the upper midrange, treble, and bass.

This additional treble energy gives more air on the stage, a better presence, and sizzle to high hats, with more sparkle and splash to cymbals when listening to Lingus from Snarky Puppy. The brass instruments also have a better-defined character to their sound without sounding shrill.

Listening to Deportation from the Babel Soundtrack, the strings sound more detailed and textured from the new 660S2. The string plucks give a more realistic sense of being played from the 660S2 compared to the original 660S. The strings also have a touch more warmth and fullness to their sound when listening to the new model headphones.

The changes are subtle sounding in the midrange, and both headphones are very impressive. If you enjoy how Sennheiser presented the midrange on the 660S, you will likely enjoy the new 660S2 midrange presentation.

Listening to Why so Serious by Hans Zimmer from the Dark Knight soundtrack around the 3:20 mark, the 660S2 dips lower into the sub-bass regions with a tighter quality to their sub-bass.

Listening next to Mountains also from Hans Zimmer from the Interstellar Soundtrack, I wanted to see how the Organ presentation differs from the two headphones.

The 660S2, between the 2-minute and 3:30 mark, presents the organ more powerfully, and the bottom end blasts with more fullness and definition, creating a more realistic presentation of what the instrument can display in this song.

Listening to the 660S2 and Thunderstruck from AC/DC, the high hat on the opening has more sizzle, and the electric guitar’s fullness and presence are also more exciting to listen to. When the kick drum comes in, it is better separated from the rest of the production on the track and hits with greater authority. Again, the sound stage of the original 660S sounds more congested compared to the 660S2.

Listening to Shine on You Crazy Diamond from Pink Floyd’s The Later Years album, around the 2:10 to 3:45 mark when the Electric Guitar drops in the 660S2 sounds smoother than the original 660S.

Final Thoughts

 So should you upgrade if you already own the 660S to the new 660S2? For my preferences, I would say yes. I enjoy the lift in the bass regions and the treble presence region to balance the increase in the bass.

The midrange is pretty similar; however, the slight decrease in the upper mids also pleased me on the new headphones giving a smoother sound in the upper mids and throughout the treble region.

This is a worthy upgrade if you are a Sennheiser headphone lover with better timbre, better separation of instruments on the stage, more depth to the low end, and less peaky-sounding treble. Now being a 300-ohm headphone, it will likely pair better with the preferences of many of us tube amp lovers.

It also presents an opportunity for those wanting an easier-to-drive Sennheiser headphone to pick up a used pair of the original 660S, which are still, in my opinion, very enjoyable to listen to even though they are now a step behind technically the new 660S2, at least for my preferences.

So as always, it will come down to your preferences. I encourage you to listen to both headphones side by side with the amplifier and source components you plan on having in your system to formulate your impressions, as we all hear a bit differently and differ on what we value or prefer in sound quality.

We have these fantastic headphones and numerous amplifiers and DACS in our headphone bar, so if you are in SoCal, stop by and hang out with us and have a headphone listening party. If you can’t make it, we have the new660S2 available for sale now on our website.

If you are interested in trading up your old headphones or other gently used audio gear for a new set of headphones, check out ourtrade-up program.We will price-match, other authorized dealers!

As always, let the music be your guide!

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