Precog's IEM Reviews & Impressions

I had the i3 briefly before returning them and going all in on the i4. Good decision at the time. Although, I didn’t have them at the same time to a/b, the i4 is a step up as far as detail and resolution from memory. They are very impressive compared to LCD5. i4’s are about 70% there, lacking in soundstage size, bass impact/rumble of the cups as expected.

I find myself keeping them just in the off chance I don’t want to mess up my hair, but with the 5’s they are getting no usage nowadays. I might put them up for sale. Not sure though as it’s hard to let them go. They are truly fantastic. I think the series gets a lot of flack because of the fitment/ear hooks. Plus having to use the Cipher cable, they are annoying, but barring subjective comfort, tonality, they are top tier sounding and highly detailed. The Cipher cable is good but not the best setup imo. Paired with my Fiio M15 and using the Autoeq settings sounded better and more resolving to me so they definitely scale and those using just Cipher are missing a better sound skipping it as most reviews are limited by it.


Thanks for the reply, I use the i3 mostly on my couch, I mostly use Roon and EQ settings, and the new hooks design work fine for me, but yes, I can’t help to think about the i4, specially when I see deals on the used market, sometimes is very tempting to make the jump and makes me wonder sound wise if is worth the extra $$.

Sennheiser HD6XX: The Critical Take

Obligatory “not an IEM”, but I’ve received a number of requests asking for more headphone reviews. This is the next installment to my series of critical headphone takes, this time taking a look at a more entry-level audiophile headphone.

The Sennheiser HD6XX was the first headphone that I purchased two years ago, and incidentally, the last one to date. I bought it because I was a newbie, it was r/headphone’s golden child, and I wanted to buy the “correct” headphone. We’ve all been there, right? Unfortunately…I wasn’t a fan. They effectively sat for months at a time in a desk drawer, occasionally being popped out to try on new sources, then promptly being shoved right back in. I can already feel those pitchforks coming out, so I need to disclaim that the reviewer in me completely understands why the HD6XX is the default headphone recommendation for $200. My aim is simply to offer an alternative, more critical perspective as to why I’ve never jived with this legendary headphone.

Bass. I’ve often stated that “the HD6XX has no bass” and - jokes aside - I do believe there is an element of truth to that. While taken as a whole the HD6XX’s bass shelf is what would be considered nearly flat to most listeners, there is a noticeable roll-off once one goes under the ~50Hz frequencies. The HD6XX’s bass neither rumbles nor does it punch then; it’s in that neutral spot with which it’s simply dead boring. It’s fair to note that this is simply a limitation of most open-back headphones; however, the HD6XX’s bass fares no better in the intangible department. Bass texturing is barely passable. Furthermore, there is little sense of “bounciness” - indicative of a transducer scaling gradations in volume, akin to what one hears on a biodynamic headphone like the PhilPhone - to the HD6XX’s bass. In general, I get the impression that one would require a severe aversion to bass in order to deem the HD6XX satisfactory in this department.

Yet, it’s exceedingly rare to find a midrange done justice when it comes to headphones, and the HD6XX’s midrange is exactly that to my ears. I’d go out on a limb and suggest that it’s even better than HiFiMAN’s standard midrange tuning, one of the few headphone midranges that I consider palatable. The HiFiMAN midrange can sound slightly forward and lacking a sense of richness at times due to a subtle recession at around 1-2kHz. By contrast, the HD6XX’s midrange generally hits more neutral-relaxed with the pattern of decay equally close to spot-on, perhaps just a tad too elongated. If you’re going to buy an HD6XX for one reason…in my humble opinion, it should be for this. Of course, it’s still not a perfect midrange. While sibilance is never an issue thanks to a gentle slope off of 3kHz, indeed, I feel that the HD6XX is almost too recessed in the 4-6kHz regions. Instruments like electric guitars and soprano vocalists are lacking that last leg of bite in conjunction with the HD6XX’s limited resolution; mind you, this comes from someone who prefers a more relaxed upper-midrange.

The general recession leading into the lower-treble also partially begets the infamous Sennheiser “veil”. Percussive hits and finger snaps come across lacking an initial sense of crack and generally sound quite dull. This lack of zest mostly applies to the mid-treble too. But your mileage will vary regarding the upper-treble of the HD6XX, as it is dependent upon the wear of the headphone’s pads. Older, more worn pads will mitigate extension and lend to a smoother top-end. This is what I hear with my unit, as treble takes a nosedive after around 13-14kHz. In any case, the HD6XX’s treble can be summarized as “inoffensive” if only by virtue of it having very little to begin with.

Power memes, source memes, and scalability memes aside, technical performance on the HD6XX is generally middling to my ears. It’s fine for $200. But there’s a noticeable gap between the HD6XX and $500 forerunners such as the HiFiMAN Sundara. This is most apparent, first, when it comes to resolution. The mostly non-existent treble of the HD6XX neuters perceived detail up-top, and there’s a rather noticeable blunting to transients in the bass and midrange.

This blunting seemingly neuters the HD6XX’s perception of micro-dynamic contrast. Individual instrument lines generally sound smeared and, as I alluded to earlier, slightly too elongated to the way they taper off. For macro-dynamic contrast, too, the HD6XX noticeably lacks a sense of punch and incisiveness when a track explodes in volume. Some might argue that this is attributable to the lack of sub-bass and lower-treble; however, I’d counter that this is beside the point. Perceptively it is not there, and the HD6XX sounds about as flat and flabby in terms of dynamics as it does frequency response. I have never found my head bobbing to music ( fine , outside of maybe the first few times I listened to it), nor do I ever find myself messing with the volume knob.

If I had a dime for every comment I’ve read from bright-eyed Redditors raving about how instruments sound oh-so-precise and distinct on their HD6XX, I’d be a rich man. And coming from IEMs, I must admit that the HD6XX sounded rather “open” to me on first listen too! Unfortunately, further listening experience evidenced that its imaging chops are within the realm of mediocre. You hear the term “three blob imaging” thrown around quite often with IEMs (rightfully so), and the HD6XX is basically the epitome of it in the headphone world. Instruments panned to the corners of center stage come across closer to 0 and 180 degrees, mushing into instruments that should be in the side channels. And do we even need to talk about center imaging? Center stage comes somewhere from the back of my head, distinct from the sides. I find my eyes crossed inwards trying to pinpoint vocalists in center stage. It follows, of course, that the HD6XX is fairly closed-in for staging, especially for an open-back headphone.

So who is the HD6XX for? Clearly, if you’re after bass, treble, or imaging chops, you should be prepared to look elsewhere. But while I wouldn’t be caught dead listening to it for pure enjoyment - for me at least - it’s still the benchmark for which anything in its price range is automatically held to. For other listeners, I wouldn’t bat an eye at it being even more than that. Especially for listeners indexing for an inoffensive listening experience and midrange tonality, the HD6XX presents an ideal first choice of headphone.


Hilariously, I just ordered an HD6XX a couple of hours ago! Your description sounds a lot like what I remember from the HD600, and could actually be applied to many basic 2 channel speaker systems as well. The reason I ordered an HD6XX is that sometimes, that’s what I want. These systems, and these types of headphones, may sound boring, but they never sound wrong, and especially for background or casual listening, that can be just what’s needed to keep me from getting distracted.

P.S. you’re using the wrong amp, I’m sure of it :stuck_out_tongue_winking_eye:


I get it, but @Precogvision, what was your chain? It would good to know just to see where you’re coming from.

This isn’t intended as a challenge as I share your take on the HD 6XX. But amps really do make a difference when it comes to technicalities like resolution, macrodynamics, inciviseness, and impact. The veil goes away - or is at least mitigated, for me, to the point where it doesn’t bother me much - with the right kind of amplification. I recently got a Schiit Mjolnir 1, a solid state amp (the prevailing wisdom is that the HD 6XX pairs best with tube amps), and the headphones were almost unrecognizable to me on first listen.

I bought my pair of HD 6XX four years ago and, for the most part, it stays in the box. I prefer the tuning HD 600: the HD 6XX is overly warm, for me, and I really dislike the mid-bass hump. The HD 6XX does indeed roll off in the treble too much for me, and the warmth, combined with the veil, sometimes makes it a bit too muffled or congested. I keep thinking I should sell my pair. But every time I get a new amp, I give the HD 6XX another listen, and I end up second-guessing myself. The Senn keeps getting a reprieve. If it were on death row, it’d be running out of appeals. I’m hanging on to it for the day when I have the right amp to do it justice, and I’m looking into getting a Starlett, which means that that day may not be too far in the distant future. Perhaps the HD 6XX will get a pardon and be spared a walk along the gangplank of a “for sale” posting.

I also keep coming back to these headphones for their mids, as you note. And I keep wondering about modding them - the mass-loading mods, I understand, help with the bass. But then again, I have a pair of Focal Clear, and they provide that extension at both ends that I find missing with the HD 6XX. I thought the Clear would replace the HD 6XX. But then the mids aren’t as rich on the Clear, and so I hold on to the HD 6XX again…

It was great to read your take on the HD 6XX, thanks!


This makes me want to buy a 6xx and Sundara just to compare against a semi older 650…

I did exactly that in early 2019, although the pads on the 650 were worn, while the 6XX was brand new; the small differences in sound between the two can be attributed to the pads exclusively in my opinion. In short, the Sundara (seemingly the original version) had better technical performance and bass extension, but the Senns had better midrange resolution and timbre. Fast forward to today, and all headphones have been returned or sold. With that said, gun to my head, I could probably be happy with the new revision of the Sundara if I had to pick only one of them as my forever headphone. Both absolutely need an amp to get the most out of them, though.


I think on the right chain for both, the 650 would probably scale better. Not sure I’ve seen the Sundara’s scalability mentioned when talking about better source gear. Again, it may, I’ve just never listened to it or heard others mention it.

When you compared both, what did you happen to use? I could see the Sundara capping out with a midfi dap or amp and sounding fairly good. I could see the 650 coming off as decent as well, until you threw it on a better tube amp and chain.

I only say this because I don’t see many Sundaras sitting alongside totl headphones and amps like some of the HD6X0s.

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I don’t want to go too far off-topic in this thread, but to answer your question, we decided to stick with source components under $500; this is because the transducer makes the biggest change in sound, and so driving a $220 or $500 headphone (Sundara was $500 at that time) with a thousand or multi-thousand dollar amp and/or DAC didn’t make sense to us (still doesn’t make sense to me to this day). So, we used a Topping combo from Drop (don’t recall exactly which), a JDS Labs Element and a Drop Hybrid tube amp (CTH) with a Grace DAC if I recall correctly.

I kept the HD 6XX around until recently, and while it does “scale” on the better equipment I’ve tried it with, it never reached the capabilities of something like a Focal Clear or Elex, an LCD-2 or X or an HD 800 or HiFiMan Arya; didn’t matter how nice the tube or solid state amp was. It’s also worth noting that all of those previously mentioned headphones still sounded better than the HD 6XX even when run on bare minimum DACs and amps like the JDS Atom or Schiit Modi. That’s just my experience, so your mileage may vary.


But how nice were those amps? The ones you list are entry-level ones, which isn’t to knock them - I’ve got the MCTH and love it. It doesn’t do the HD 6XX many favors although I’ve heard worse pairings.

My post above was really to point out that any review of the HD 6XX needs to identify the amp paired with it because the amp matters so much. Since the HD 650/6XX is arguably the most famous headphone for its ability to scale, impressions should be of the amp and the headphone together as a single unit, otherwise the frame of reference is absent, which has a significant implication for how we can understand those impressions.


Sorry, I didn’t mean to open a can of worms with my snarky amping comment. The official HD650 thread seems like a good place for further discussion on amp pairing.


Respectfully, I disagree. The HD 650/6XX does indeed scale, but not so much that it outclasses the headphones I mentioned above, even if they’re paired with entry-level gear. The 650 sounded good on the Feliks Audio Euphoria, but it still had its limits. At that price, it would make more sense to pair the Focal Clear or LCD-X with a Rebel amp, at least for me. I do not believe the 650 drastically changes with every different amp it’s used with, thus I don’t agree that it and the amp should be considered one unit. It’s a great headphone in the $500 and under segment, but it’s still very limited to my ears. If your experience differs, that’s great though! But based on my experience, however, the transducer has always made the biggest change in sound - for better or for worse - so that’s where my money goes. I’ve not heard anything yet to change my mind, but perhaps one day.

Mods, sorry for the off-topic convo. Please move to the HD 650 thread if necessary. Sorry to @Precogvision for the derailment as well.


It’s all good man. I wrote this review using my DX300 on high gain, but my comments are intended to be an aggregate of everything I’ve listened to it off of including the DX160, AK SE180, AK SE200, iFi Micro Black Label, and Burson Conductor 3XP.

I should also note that, ironically, the 3XP probably sounded the worst of these sources to me. Sounded like it had no micro-dynamics and generally just made every HP I tried off of it sound sort of flat.


I can’t say that I disagree with your assessment on the whole: three blobs, limited dynamics, rolled off ends, etc. However, my main take away from the writeup was to see where you are coming from versus where the Redditors who are:

If you were coming up from below it would indeed be relatively wonderful. Benchmark it versus a Skullcandy or a $100 set of Beats. It’s affordable to a younger crowd who has trouble finding a spare $100 for anything.

I concur with @Tchoupitoulas about the subtle draw of 6XX and 600, and still go back to the 600 for easy going background music. It won’t wow you, but that’s not the point. I also concur with @Nuance that amps won’t perform miracles. The 600 family has absolute technical limits, which can be readily found with balanced amps (more value with the 600, less with the 6XX). Those plastic drivers tend to resonate oddly and are very sensitive to noise/harmonics, which helps explain scalability or chain transformations.

The 600 family delivers a chain puzzle for finding different outcomes. If you start cold and focus on the music it’ll keep you happy.


I’m glad you said based on your experience. I think there are others who have had other experiences where source/amplification play a huge role in sound and invest much more in the front end compared to the transducer. I understand that in the beginning of the hobby, most people are recommended to spend the most money they can on the headphones. It’s true that without a resolving headphone, it doesn’t matter what you put in front. However, there is a point where good transducers will get better the better you feed it.

Honestly there’s nothing that will really convince you unless you listen for yourself. Hopefully you’ll get to that point in your journey cause based on my experience, source can present music in very different ways. It’s a little crazy how much source rolling happens when you go beyond the bifrost2/ares ii level.


You realize the conversation was mainly about the HD 6XX right? I never said amps and DACs don’t make differences, but rather that 6XX/650 hits a limit where they cannot further improve it, no matter the cost.

With better transducers, of course you’ll more easily hear the benefits of your higher end source gear. I’ve experience it numerous times and I’ve reached that level on my personal system. Why would you assume I haven’t? Because I said the transducer makes a bigger difference (which it does)? I think we agree more than you initially thought. :slight_smile:

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We realize this, and many people (including myself and I think DB) would disagree with that assessment.


That’s fine - never said mine was the only experience that matters.

For what it’s worth, I think investing more in source gear is a good idea once you find your ideal headphone. But if I only had an HD 650, I wouldn’t sink too much into it. To each their own, though.

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I’m just curious, what was the cost (and gear) that you put your 650 on when you made this decision that you can’t improve it any further?


DACs we’re from Schiit and Mytek; amp was mentioned above (Feliks Audio Euforia). For me, the 650 hits a limit and isn’t worth listening to on gear kilobuck gear; I’d much rather purchase a better headphone and start the gear pairing journey over again. If the 650 doesn’t limit out for you though, cool. Enjoy!