EDIT: 7/7/16
I am redoing this review I posted in 2015 because it was too short. For this review of the HD650, I will be going into much more detail about the sound, pros and cons, certain tracks that make these headphones shine, and how DSP plugins can make this headphone (or pretty much any headphone) come alive.
First, let's go over the build quality and comfort.
The HD650s are completely plastic on the outside, except for the metal grills and metal adjustment band. For the 2 years I have had them so far, there have been no paint chips or places where the paint has rubbed off from use. Keep in mind, I have taken extremely good care of them, and made sure to never place them on hard or rough surfaces. If you do that you will find the paint will come off eventually as others have said in their reviews. I really like the gray color all around, and personally like it better than the HD600 and HD580 design and color.
These are the second most comfortable headphones I have owned, right behind the Beyerdynamic DT800/T1. The clamping force is tight at first, but over time it loses that tightness and stays comfortable. I have a narrower and taller head than many, so I need to click the headband adjustment down 9 clicks in order for it to fit over my ears. These also weigh very little, and there have been times where I've worn them for 4+ hours and forgot they were on my head. I used the original pads for about a year before I replaced them, and then recently replaced them again a few month ago, but they have compressed quicker than the other 2 pads for some reason. I suggest before you buy replacement pads for these, make sure they aren't fake and are from an authorized Sennheiser seller or from Sennheiser themselves, because I may have gotten fake ones since they got flat in less than 5 months. Flat and compressed pads really affect the sound negatively and caused my pair to have more bass in one cup than the other.
For reference, I am using the JDS Labs ODAC with the Objective 2 amp. Yeah, many people on this site will criticize me for using such a “lowly” source and amp, but they sound good and are neutral and flat, as they should be. The O2 powers my HD650 very well. Also, I do not believe in cables making a difference in sound, so I am using the stock cable, which is plenty durable enough for years of use. Let's just say I'm a bit objective when it comes to audio tech.
If I were to describe the HD650s sound in one word, it would be natural. Very natural, smooth, and non-fatiguing. I remember first listening to these, and saying to myself, "FINALLY! A headphone I can LISTEN to!" These have no exaggerated lows, mids, or highs. I keep telling people that these remind me very much of high quality speakers. In general I like the way speakers portray music more than headphones, but I am starting to rethink that as the HD650s immerse you even more than speakers in my opinion.
Starting with the lows, these have a somewhat relaxed bass tone. The sub bass is definitely there, but is not emphasized, and may be very slightly rolled off. Compared to planar magnetics, these lose the sub bass battle, but I am ok with that. I have experimented with EQ in the 25-50 Hz range, and found if I raise this area by about 4 decibels, the sub bass is more present and not distorted at all. The mid bass and low mids are raised ever so slightly, giving the headphones that lush and warm feel I love so much. Yet, it does not affect the rest of the frequencies, and makes recordings with little information in this range sound smoother and and less analytical.
The mids are where this headphone beats pretty much every headphone I have tried ever. The mids are incredibly realistic and natural, and makes instruments sound like the instrument they are supposed to be. Compared to other headphones such as the Hifiman HE-400i, Beyerdynamic DT800, and even the T1, the mids outclass them all because of how natural they sound. I feel with those other headphones, the mids are overshadowed by the higher treble response giving the impression of the mids being sucked out. They have more of a V and U shape response as opposed to the HD650s flatter response. Yes, many will say the mids in the HD650s are emphasized and too lush, but the very reason I have fallen in love with their sound signature is because of the smooth mids and treble. Many headphones just sound too analytical and sharp in the mid to treble region. Not so with the HD650s.
Speaking of treble, these have probably the smoothest treble I have heard from any sound reproduction device, speakers included. There are no peaks in the treble, and that is why these sound so smooth. These are never fatiguing, and are perfectly suitable for even the worst recordings (examples of which I will add to the music section). And with that note, there is something very important I need to address about the HD650s: the dreaded “veil”. Simply put, these have no “veil” and I don't understand why people keep saying they do. The high frequencies are present, and do NOT roll off. The treble extends all the way to 20 Khz, and frequency graphs support this. Perhaps before these headphones got revised in 2007, they had some sort of veil. But this new version has just as much extension as the HD600. So, these have plenty of treble detail and extension, just enough for me to not get fatiguing. Sure, compared to the T1 and Hifiman HE-400i these have less treble quantity, but the quality is exactly the same in my opinion. Even if the treble is less present than many headphones, I find it strikes a perfect balance between natural and realistic.
Now, I will list a number of music examples that I find bring out the HD650s strengths, and maybe a few of it's weaknesses:
This is a very well recorded piece of classical music, a genre I find the HD650 to excel at. In the beginning and in the middle of the piece there is a timpani on the right side and with the right headphones, sounds incredibly realistic. The HD650s make me sometimes believe that the players are in the same room! Just goes to show that with well recorded music, headphones sound their best.
No doubt everyone has heard this electronic piece from the 80s. This is one of the better recorded versions, and really shines with headphones with extended bass. The HD650 doesn't do as well in the sub bass as say planar magnetics, but I find them to be at a realistic level of what the mastering room would have heard the recording. If I want a little more bass, I just EQ the 25-50 hz range up a few decibels. Also, there are subtle treble details in this composition that the HD650s bring out beautifully.
Bet you saw this one coming, an extremely popular song that sounds incredibly good on good headphones. In particular the vocals are without sibilance and the drums are at the perfect level. The HD650s bring so much out of this recording, including the detail in the drums. Why can't music be mastered like this anymore?
I put this one on here because it is a harsher recording. The solo vocals were obviously recorded with a lot of compression and sounds like someone turned the treble all the way up on their big chunky 80s equalizer. On the Hifiman HE-400i and Beyer DT880, this song is almost unbearable. But, the HD650 tones down the harshness just enough, but still is revealing of the harshness.
Yes… I know… It's a Backstreet Boys song, but bear with me here. I chose this song solely for the only reason to show how the HD650 makes harsh recordings sound better. This one, in my opinion, is even harsher than Broken Wings. At the 0:48 mark, there are cymbals and really harsh vocals that have a lot of presence. I've listened to this on the AKG K712s, and it is downright PAINFUL. Thankfully, the HD650s save the day once again, and turn down the harshness just enough without sacrificing detail.
This is an incredibly beautiful rendition of Pachelbel's Canon in D. And, it is spectacularly recorded too. With the HD650, it's easy to get lost in the sea of the ambiance this piece has. The slight mid bass bloom the HD650s have make this piece incredibly immersive and lush. And everything sounds very realistic, especially the strings and plucked instruments.
This is extremely impressive on any headphone, but especially the HD650s. The cello on the left at the beginning is so darn realistic because of the binaural recording that Dr. Chesky did. Really, you can't go wrong with any of the binaural tracks that Dr. Chesky has made, because they are meant for headphones and make you feel like you are really there.
By the way, I didn't purposely pick videos that have the same music album info layout, those were just the best quality I could find on Youtube.
Next, I want to talk about how you can squeeze every ounce of sound quality out of the HD650s: Digital Signal Processing.
Many people are very much against DSP plugins, but if you use them the right way, it can be a transforming experience.
There is a software plugin called Sonarworks Reference 3. Used mostly by recording engineers and music producers, this plugin takes your headphones or speakers and calibrates their frequency response to be reference monitor flat. Basically, the program equalizes the response of your set of headphones, and makes them suitable for mixing and mastering in a studio.
As you can see here, the program takes the average frequency response of the HD650 and corrects any deviations from whatever curve you select, whether it be flat, B&K curve, or your own custom curve. The blue line shows the average response of the HD650s, and the green line is the correction curve. It claims to have an accuracy of +- 3 db across the whole range, and it certainly sounds like it to me. They also have an option to send in your headphones to be measured and calibrated, having an accuracy of +- 1 db. This is a very good option for those who want the convenience of headphones, but have the sound of accurate studio monitors. Or, like me, someone who want the most accurate sound possible. I have also tested the AKG K240 Studio with this software, and to my surprise they sound strikingly similar to the HD650 when calibrated, at a significantly lower cost. The correction curve makes the HD650 have great sub-bass response, less mid bass bloom, and even smoother more present treble. Even with the default calibration, this program makes the HD650s sound like speakers, and that is what I've always wanted in headphones.
The fun doesn't stop there! I have been using the ToneBoosters Isone VST plugin for about a year, and it wasn't until I used it with Sonarworks that I was blown away by it. Essentially, this plugin gives you the option to emulate a 2 channel studio environment, complete with room size, reflections, and even an anechoic chamber. I use this plugin mostly for it's crossfeed settings, but with the addition of the Sonarworks software, the results are shockingly convincing. After adjusting the HRTF to meet what I find my head and ear size to be, I could swear there are speakers in front of me producing the sound. This is what I imagine a poor man's Smyth Realiser would be. In fact, I would go so far as to say it sounds
better than a really good 2 channel speaker system, because you have a controlled simulated environment without any room imperfections or resonances. Technology has really come a long way with these plugins, and I wouldn't be surprised if 3D audio became a mainstream thing in the years to come.
Comparisons:
Vs. HD580
I bought the HD580 2 years ago before I had the HD650, but I remember the sound well enough to describe the comparisons between the two. The HD580 did not have enough bass for me, and they seemed to roll off to my ears in the upper treble. The HD650 is more extended at both ends, is warmer, but has pretty much the same midrange. Since the HD580 and HD600 are similar but the 600 is an upgrade, I would assume the HD600 has just as much extension as the 650.
Vs. Hifiman HE-400i
These headphones were amazing when I tried them. I was floored by their flat extended bass all the way down to 20 hz. In the end I returned them because they were too analytical sounding for me. There was enough bass, but the midrange was overshadowed by the treble peaks and made things sound unnatural in the end. However, these do have better treble detail than the HD650, but it is directly a result of higher treble response, not of treble quality. In fact, I have experimented with EQ to raise the HD650s treble higher, and got a very similar result of higher treble detail. So, these beat the HD650 in sub-bass only for me. Also, I would say the HD650s have better soundstage than the 400i.
Vs. Beyerdynamic DT880 + T1
It's been a while since I have had these two headphones, because I have sold pretty much everything since I started using the 650s. Both Beyerdynamics have great treble detail and clear crisp sound. However, I did not like either for long listening sessions, because of the painful treble peaks Beyers are known for. Compared to the 650, both Beyers have less lush mids, more treble, and about the same bass, but both are more extended. These both are on the list of the Sonarworks software, and I have yet to try them with it, as I am sure the software will tame the peak very well.
Vs. AKG K712+K612
Again, it's been a while, but I remember the AKGs excelling in soundstage only. The K712s had slightly more extended bass, but lots of mid and treble peaks that made things sound weird. The K612 had less peaks, but the midrange was a bit unnatural and analytical. Again, the K712 is on the Sonarworks plugin list, so these can be corrected to sound flat and probably maintain that better soundstage.
Final thoughts:
I have gone through at least a dozen headphones in the past 3 or so years I got into the hobby. I have since sold pretty much all of the ones above $200, except for the HD650. That should tell you how good they are, that they even outclass the flagship Beyerdynamic T1 in my opinion, at least when it comes to natural and realistic sound signature. I have yet to try the HD800, but if I were to make a prediction, I probably will still like the HD650 better. If you are into lots of treble detail, these will probably not be for you. But, if you like a smooth sound without peaks across the whole frequency range, these should be on your list to try. Thanks for reading!
