Build Quality & Comfort
Like its brothers, the new Sennheiser HD660 S is also made in Ireland. Looking at the limited differences in design, that’s only a normal decision as well. Quality wise, Sennheiser did make one very important improvement however. As you probably know the “old” HD600 and H650 headbands suffer from paint chipping away when they’re heavily used (see pic). With the new color scheme and paint job, this no longer is or will be the case. In fact it’s not new as Sennheiser already addressed this in their Massdrop HD6XX headphone.
According to Sennheiser the robust yet lightweight construction makes listening supremely comfortable. The elliptical ear cups are shaped to follow the anatomy of the ear, while thick padding on the headband and the replaceable ear cushions provides a relaxing and luxurious experience that places the enjoyment of music at center stage. We already know this from the HD600 and HD650 of course and with only 290g, the HD660 S simply is one of the best fitting and most comfortable headphones on the market. You can wear it for hours and it won’t bug you for a minute, I love it. If you have a really big head however, you might find the clamping force of the HD660 S to be a bit much. But just like with the other Senns that can easily be addressed by stretching out the headband by putting a couple of books between them. It’s nothing to worry about.
Everything about the HD 660 S makes listening a pure pleasure – not least its strong yet lightweight open construction. The elliptical ear cups are shaped to follow the anatomy of the ear, while thick padding on the headband and the replaceable ear cushions guarantee hours and hours of listening in supreme comfort.
The former HD6XX models always came with a single long copper based cable, finished with a 6.3mm plug. The 300Ohm headphones need an amp to sound best so this was only a normal choice. Back in the days the audiophiles weren’t as occupied with balanced connections as they are now, so there was no real need for balanced headphone cables cables either.
On top of that Sennheiser only recently officially confirmed to adopt the Sony 4.4mm Pentaconn balanced connector and this connector now also is incorporated in their new HDV 820 DAC/amplifier unit. That in combination with the fact that the new HD660 S with its 150Ohm impedance is a lot easier to drive, made Sennheiser supply a 4.4mm finished cable as well. We’ll get into detail about this later but the Sony NW-WM1Z and HD660 S combo in balanced mode really is something special sound-wise.
Because of the HD660 S being easier to drive (Senn is even promoting the HD660 S in combination with DAPs), Sennheiser also includes the typical 3.5mm Grado adaptor in the box. So in the end you have 3 full-fledged cables to use with your new HD660 S. Well done Sennheiser!
Actually, it turns out I never officially reviewed the HD600 and HD6650 myself, Dave did that for us. That might come as a surprise as I’m always saying good things about them and because I use them in almost every single review. To me the HD650 still is “The King” and of the 6-series I now own the HD600, HD650, HD6XX and HD660 S.
“The headphones deliver an exceptionally accurate and transparent sound that also has an expressiveness that immerses you in every emotion and nuance of music.”
Before going in to the HD660 S even more, let’s quickly recap what the HD600 and HD650 sound like. The HD600 is the fastest of the three, and it is a headphone that is loved by many rock fans for its pace. The HD600 has great clarity and has a more neutral tuning, but always with a musical approach. I actually started my Sennheiser journey with the HD600 and I loved it. That was until I also bought the HD650 and it quickly won me over with is slower, warmer and smoother tuning. Some say the HD650 sound veiled and dark and while I see what they mean, I would put it that way. And fact is that your source is very important in this story, as it will alter the end result.
Made for the demanding listener, the HD 660 S surpasses the exceptional performance of its predecessor, the legendary HD 650. With a crisp bass, excellent mid-frequency response, and a gentle, pleasantly natural treble, the HD 660 S has an expressiveness that immerses you in every emotion and nuance of music. Still, it always stays exceptionally accurate and transparent
So basically there are three groups of people: those who like both headphones, those who prefer the HD600 and those wo like the HD650 most. Going on how the HD660 S sounds, it to me is clear that Sennheiser designed this headphone to (try to) please both groups of people. The HD660 S has the speed, transparency and clarity of the HD600, combined with the bass, naturalness and musicality of the HD650. It’s like the perfect headphone if you can’t decide which of the “old ones” you like most. Those not liking the “veiled’ nature of the HD650 will love the more clear HD660 S and those who find the HD600 too sterile, will love the more natural HD660 S. How can it not be a great headphone?
More Sound + HD600 & HD650
The Sennheiser HD660 S of course is a fully open headphone and you get a really nice wide and deep sound stage with a very natural sense of air and spaciousness. The overall pace of the HD660 S is more like that of the HD600 but it is not exactly the same to my ears either. It definitely is quicker than the HD650, there’s no doubt about that. The mids are very much like those in the HD650 on the other hand, and you get a natural, somewhat smoother delivery with a very high musicality factor and exceptionally good voices. The HD650’s bass isn’t as tight as the HD600’s or HD660’s bass and the HF660 S’ bass is tighter and faster than that of the HD650. If you Google for the FR curves you’ll be surprised to see these 3 headphones, up to the treble part, actually are very close together. This however doesn’t translate identically when you’re listening to them. The bass, mids and treble in all 3 headphones are different. And it might even be the treble section in which they’re most different, the HD660 S is very particular in that area.
The blackness of the background still is typical of Sennheiser but what I really want to talk some more about it how using the balanced cable changes the sound signature. Actually it’s not only by changing to balanced that the sound changes, the source used also impacts the HD660 S’ performance quite a lot, but more on that in a bit. When taking the Sony NW-WM1Z as source it is quite easy to switch between the single ended and balanced output. With the SE output you get a more neutral and fast presentation, with (again) a neutral amount of bass and treble which is more to the forward and slightly brighter side. Switch to the 4.4 balanced cable and you’ll get bass with bigger impact, more musical and slightly thicker mids and softer, yet still energetic treble. Especially the bass presence using the balanced output is impressive, but it really affects the mids, voices and treble as well. It makes the HD660 S sound more like the HD650 where the single ended cable makes it tilt more to the HD600 side.
Even more on SOUND on Page THREE of this review, after the click!