An Embarrassment of Riches

In the midst of reviewing the new Acoustic Research AR-H1 I found myself feeling the need to compare it to other open headphones newly relevant to the price point.

*doorbell rings*

Sweet! Sennheiser's new HD 660 S on the stoop. Must measure now! A quick call to Audeze while measuring to ask about availability of the LCD-2 Classic. Woot! Production units are in, Sankar is sending one for Saturday delivery.

Well crap. There goes my AR-H1 post for today...looks like a working weekend. Should be able to post an AR-H1 review on Monday and an LCD-2 Classic by next Friday, and the Sennheiser for the week after. I did check on HiFiMAN's Sundara...still a few more weeks to go on that one, hopefully by Christmas. Gonna be a busy few weeks.

Anyway, by way of apology for not getting a review out today I'll offer up the HD 660 S measurements...without comment.

Click on graphs image to download .pdf for closer inspection.

Have a great weekend!

Ranstedt's picture

any estimate when that review might be ready?

hanshopf's picture

My bet is, that Tyll will find the Clear better than Utopia.

Tyll: try them with Elear pads. With these I find them nearer to ideal than any other headphones I experienced. Strangely the Elear pads did not improve Utopia in my opinion, but very clearly do with the Clear, which has perfect higher treble (contrary to Utopia), but a bit too much presence instead. Not so with Elear pads.

I also find the Clear to be technically better (more controlled) then Utopia, while still offering the same or almost the same very high resolution.

I sold Utopia and "upgraded" to Clear...

metal571's picture

Comparison of all current 6x0 cans now using Sup's bot, with Harman compensation.

Johan B's picture

Those measurements look like an AKG K240.

Johan B's picture

Probably sounds less neutral. And not good at bass?

detlev24's picture

Indeed, it differs a lot from what is considered a natural frequency response as of today [HARMAN target] and the bass-region you mentioned would be a big concern to me in this specific example:

With such a high base THD+N, I would not even bother to EQ the headphone, as it would create an even higher amount of audible distortion!

Maybe's picture

"high base THD+N"
Are you sure about that? 1% (-40dB overtone) at 40Hz at 90dB isn't too bad and will most likely be overshadowed by PC-fans in the background.

If you usually listen at 80dB max you can definitely EQ the subbass up by 5dB without hitting noteworthy distortion values.
Furthermore, the Senns distortion in the bass is predominantly 2nd Order and above 100Hz THD is rather excellent.

Not saying the 660S is a good buy at the current price of 500USD, I simply find the importance of the THD+Noise measurement to be grossly overrated with people thinking they can detect harmonics below the noise floor.

detlev24's picture


I completely agree that probably nobody will be able to hear 1% of distortion at 40 Hz. Furthermore, I understand that 2nd/3rd harmonic [euphonic] distortion sounds pleasant to many listeners. Nevertheless, I am sure that for my purpose of listening with as much accuracy as possible, this headphone would never find consideration due to the previously mentioned. Let me explain:

Our hearing is least sensitive in the sub-bass region [see ] and some headroom well above 80 dB is essential for peaks; especially when going down to 20 Hz - which is one entire octave below 40 Hz, I would not want to miss!

If we take the 'B&K 1974 optimum Hi-Fi curve' or any recent aberration like the HARMAN target, +5 dB of correction in the sub-bass region would probably not be enough for this headphone to follow the target; although there will be a gentle roll-off most probably before 20 Hz - to not overstress the drivers. Distortion already is at an audible level in certain conditions and it will further raise with EQ. Consequently, headroom at least for peaks will be limited in terms of accurate bass reproduction.

Let me show you an example with an average calibration profile for the Sennheiser HD 650; which has a similar sound signature. [The following frequency response is translated to what loudspeakers measured in an anechoic environment would show.]

BLUE = measured average frequency response (of many samples)
RED = target frequency response [B&K 1974]
GREEN = correction

MAGENTA = corrected/final frequency response

Since the HD 660 S seems not to be a completely new development; even for people who love it, it certainly is not a bargain at $499.95 (or even more in other currencies).


Maybe's picture

Thank you for further explaining your point.
When using aggressive filtering towards a bass boosted target curve and listening to highly dynamic music I understand that the 600 family's bass performance will not suffice.

I think the 600 series main appeal is that they don't need alot of filtering to sound decent. Apart from the underwhelming bass they're probably some of the best in terms of offering a linear, pleasant response which is probably why so many vinyl enthusiats who can't make use of finely adjustable digital filters enjoy it so much.

Certainly, if you know how to use an equalizer or have Sonarworks, frequency response has a low priority when considering a headphone.
What would you choose over the Senn in this price range? K712s and DT880s? Both handle bass quite a bit better than the 6XX.
Of course, STAXes would be ideal.

detlev24's picture

Well, maybe(!) especially elder people prefer a linear frequency response due to the normal loss of hearing in the high frequencies. Although it is true that our brain adapts and therefore a natural frequency response [as by the target(s)] will always be perceived as natural; I understand that some extra energy where hearing loss occurs, might enhance the listening experience for some listeners. [I personally cannot tolerate a linear frequency response with many songs, since to me it sounds too high-pitched and thus creates stress.]

Because of manufacturing variances even amongst the same series of headphones, I would suggest you choose primarily by listening. However, just by looking at Tyll's comprehensive measurements and the averaged profiles by Sonarworks [only the 250-Ohm DT880 available] I would expect to find a more pleasant overall-experience using the AKG K712 Pro. Regarding EQ, I would also consider the HiFiMAN HE-560, which now comes at $499.00 (I cannot recommend its connectors, though^^).

GNagus's picture

Is the HD650 to be discontinued? In fact, as i look at these measurements, I don't see why Sennheiser can't simply sell these, lower their price by $100, and discontinue the HD600/650 headphones.

tony's picture

Lovely prose.

I still love the HD580,600 that I purchased in 2011. ( hafta get the HD660 too )

Sennheiser anchors the entire headphone world. god bless em!

Tony in Michigan

ps. headphones aren't any good unless they can out-perform Sennheisers

zobel's picture

...Still a lousy bottom end. I don't listen to my HD600 at all any more due to its poor frequency response, which makes it play second bass (pun intended) to my other cans. I kind of liked it, though for the past 19 years....but.... yawn....they have no real dynamics, and put me to sleep. The AKG K7XX is better, the Amperior is superior...

cspirou's picture

Any interest in reviewing the Shinola Canfield headphones? While they are definitely fashion 'phones and you are paying a premium for looks, I think they are promising since Alex from Audeze is involved in manufacturing. Plus these are the only closed metal headphones since Sennheiser discontinued the Amperior.

potterpastor's picture

I enjoy your well prepared and well researched reviews and we are really looking forward to an analysis of these new open back headphones.

I purchased the Sennheiser HD 579 for 99 bucks on Cyber Monday. I’ve been enjoying them for the past few days. They sound almost identical to the HD 598, but less warm in the upper bass. My wife and I have switched back and forth between the two, and she can’t tell them apart. They sound more forward and exciting with the Oppo HA2SE.

They also sound similar to the Hifiman HE400s, they are both a bit light in the sub bass. But I have the VModa Crossfade 2 on the wire when I need me some bass, So these are a very good counterpart to something more bassy.

amartignano's picture

It's really amusing to see people judjing as terrible a set of measurements like this. To me it seems one of the most balanced behaviour seen in the last times. Very good impulse response, smartly voiced frequency response (a tad descending with frequency but with a touch if sparkle, end very smooth overall, no important peaks or valleys), good THD with normal "warming" increase in the bass. I love my Hd800S, but the HD660S measures good and plays even better than the measurements.

GNagus's picture

There is so much more to headphones (and speakers for that matter) than measurements. This family of headphones (HD580/600/650/660s) wear comfortably and offer relaxed sound. I own the HD580 and while I haven't heard the 600, 650, or this new 660, I am certain I would like them and find them familiar.

Certainly the bass doesn't extend as deeply as other headphones do; they are open headphones. Open headphones don't generally reproduce 30Hz and below if that is what you need your headphones to do.

The Grado SR325 (all versions) are not very comfortable and have a frequency response that look like the Himalyas. Yet, they offer a certain sound that none of the competitors offer and that many people seem to like.

I've never tried the HD700, the HD380, or the new Grado RS1e. The RS1e's measurements look bad, the HD700 looks hideous and its FR has a peak in the treble, and the HD380 has a FR that I like with good isolation, but Tyll said he preferred the HD280 instead. So, I'll need to listen to these headphone to know if I would like any of them and if I decide on measurments only, I may be disappointed or miss out on something i like.

amartignano's picture

Agree: as an example, I see the strange HD700 measurements, nevertheless it's an headphone that often I love to listen, especially with symphonic orchestras.

elwappo99's picture

I think the general consensus is the Grado and HD700 sound pretty much like their graphs. Most people find them bright and difficult to listen to.

amartignano's picture

For me the Hd700 sounds way more balanced than bowls-padded Grados (while comfie-padded Grados seem also balanced to me), nevertheless I understand that the 6 kHz pick/ringing/whatever can bother many. It doesn't bother me especially in classical where my brain pay more attention to the soundstage effect of the hd700's response.

Johan B's picture

I am glad you are amused. I shall stick to my more amusing Hifiman H400S.

amartignano's picture

You're entitled to :)

inmytaxi's picture

So I ordered a set of headphones from Audeze's site on Tuesday am and have heard NOTHING yet you have something coming in for saturday delivery?

I see where Audeze has it's priorities.

halcyon's picture

What a disappointment.
This is what Sennheiser is able to come up with after 20 years of driver, materials, engineering, measurements and psychoacoustics development.
Really sad.

amartignano's picture

Oh my god, also here it's judjing without listening headphones moda. Sennheiser has done a lot in terms of resesearch, we have the Hd800s. This is an hd6** series headphone, and surprise! appears and sounds alike. Just (for me) correctly improved. Maybe I would have dared a bit with slightly angled drivers in a very similar structure and slighly different pads, but... they were very conservative with the hd660s, but they've done imho a very good headphone.

GNagus's picture

Virtually identical measurements to the HD650 while being easier to drive.

amartignano's picture

It's very similar (obvious given the same enclosure), but the Hd660S seems to me more even from mid up. It's indeed astonishingly similar to the frequency response of the Hifiman he400s.

GimmeCans's picture

Might I suggest the Beyer Amiron as another contender at (well, near, anyway) this price point?Just took delivery of mine and, so far, finding it a significant improvement over my trusty 650's. Significantly higher resolving, almost planar-fast, 'unveiled', and better comfort. Listening to Joey deFrancesco's 'Wonderful, Wonderful' right now & the sound is VERY smile-inducing.) Unless the 660S steps up the 6** series game pretty significantly (it doesn't seem to measure all that differently judging from the measurements), I think they may have a problem with this model at a modest $100 more. Consider this a review request please, and keep up the good work.

GimmeCans's picture

It would be great to be able to edit one's post. Just a suggestion.