[C.C.S.]

About two weeks before Christmas, I had the pleasure of receiving a pair of KRK KNS-8400 studio headphones and a Fiio E11 portable amp. I've spent about an hour to three hours almost every day since then, listening to these headphones and I feel like I know them relatively well now. So, on to the review...
 
Construction Quality: These headphones are built very well. They are built mostly in plastic but also feature metal in their construction. Overall, it feels very solid. A soft carrying pouch is included, and unless you were trying to carry these with a bowling ball in the same bag, I would not even waste a second thought on them. They could take a fairly decent amount of stress without succumbing to failure.
 
Comfort: These headphones are extremely comfortable due to their memory foam padding and their just-right clamping force. The only issue here is with the space between the two pads on the headband. After slightly extensive listening periods, these will create a small point of discomfort on the top of your head. However, this can be fixed by simply shifting the headband a little bit forward or backward into a new resting position. They do not get very hot, though they are warm enough to double as ear-muffs in winter cold. Anybody who walks in winter weather will experience extra comfort with these on.
 
Sound Quality
 
Bass: Down low, the KRK headphones do a lot of things right. There is a decent amount of bass impact. They will not slam your head around but most listeners should feel just fine with bass impact. They extend quite low, down to even the shaky, rumbling bass that some hip-hop songs love to parade. But, again, these sounds are not a dominant force. They can be heard and they can be felt, but so can everything else. Mid bass can be a little bit too quiet sometimes on bass-light songs. When the bass guitar is used as a background instrument, it sometimes almost feels lost in the mix. But, it's there. The clarity of the bass on these headphones is worthy of praise and it's detailed all the way down to texture. Bass strings that are plucked or slapped sound obviously different from ones that are lightly picked or strummed. But, in addition, they feel different. Ones that are slapped feel percussive like they should. And when strummed, there is very little feeling to them unless they are very low, in which case you can feel the strings vibrate. This results in a very cool experience.
 
Mids: The middle frequencies can best be described as being balanced. They are reproduced effortlessly. Everything that should be heard is played in the exact same way as it should be and the headphones never sound strained. The same texture qualities described in the bass are also present in the mids. When listening to a singer that uses a lot of air, you can feel the air push through your ears, almost like a light wind. A wind instrument possesses the same quality. You can both hear and feel the air move around you. This also makes the soundstage feel fairly large for a closed back headphone. It is certainly not huge, but there is noticeable space between performers in small groups and a large symphony will sound like it is coming from a moderate distance in front of you, or from all around you in different directions, depending on the recordings and the concert hall.
 
Treble: Higher frequencies on the KRKs are remarkable. They remind me a lot of my HiFiMan RE-Zeros except in a full-size headphone. They extend a great deal, rarely exhibit sibilance, and are very neutral. There is a good deal of space in the upper register and that same airiness is here as well. Flutes and upper register strings sound incredible on these headphones. When I close my eyes, the strings have me under the illusion that I'm sitting in Cordiner Hall listening to a live symphony. Cymbals of all kinds are also exceptional on the KRKs. There is honestly very little fault to be found in the treble except that it is definitely not meant to be played loud. The bass and the mids would probably be listenable at higher volumes, but any treble that is played sharply in the recording (usually cymbals) will sound very piercing when listening at louder volumes. I made the mistake once of listening a bit too loud and a cymbal almost cut my ear. At normal to just a bit above normal volume, these will sound wonderful, but if you crank them up, you will not be pleased.
 
Note: I wanted to point out that the timbre and tone of these headphones is something special. Especially in wind instruments and percussion. Listening to any wind symphony is an absolute joy with the KRKs. Also, these things present tons of detail. They rival my RE-Zeros on detail retrieval, and though they don't best them, that's still mighty impressive to my ears.
 
Conclusion: These headphones are a new favorite of mine. I'm sure there's equipment out there that sounds even better, but for now, I'm more than happy with these. At about $120 from most online retailers, these are a great deal. I feel that they could easily take on most of the $200-$250 price range and stand their ground. In addition, they feature user replaceable cables and are very sturdy, so there's no need to worry about these headphones failing. I feel like these headphones were made with everybody in mind. They've got superb sound quality at a more than reasonable price. They're built to last. And despite their moderate sensitivity and low impedance, they still benefit a bit from having the extra power from an amp behind them. So, I give these a 5/5. Not for being 100% totally perfect (I feel like that midbass could come up just a little bit), but for being close enough for me and from keeping me from really wanting that next big upgrade.

 

[tdockweiler]

Very nice review! I read every single word and there is not much there I don't agree with. I'm so glad you mentioned that the treble can only be a problem when the volume is cranked loud due to specific recordings. These are definitely not even remotely forgiving of source IMO.
 
I have a few very badly recorded and harsh sounding tracks and it doesn't touch them and still sound bad. If I want something to tame them a tiny bit I can use my HD-598 for that.
 
I usually prefer open headphones due to the larger soundstage, but these make the pass from me because it's still quite large (not huge and depends on the recording of course) and very accurate.
 
There's not much bass impact on my pair also. A tiny bit. The KNS-6400 has a bit more mid-bass, but less sub-bass it seems. The treble on the KNS-6400 seems a bit less sharp and it's like comparing the treble of the K601 to the K702 I guess. Maybe even the SRH-840 to the SRH-940.
 
My only complaint is that they're kind of loose if you've got a small head. If I move my head all around or say listen to these in bed, they'd fall off. Not a big deal. I have found a way to make them have more clamping force for me, but it's a very, very huge risk and could crack them. Somehow they handled the challenge. They're a bit too awkward to wear in public. Seriously these things could fit King Kong! If you expand them, it's like they could fit anyone!
 
I also noticed that with both models they comfort isn't at it's best on the first day. It seems like after a week the comfort really improves. It's almost like the pads break in or expand a bit. It's kind of hard to believe, but I noticed this with both types of pads. I also like to stretch them out a tiny bit and maybe that helped.
 
For competitive gaming, they're also a hidden gem. More people need to try these for gaming when a closed headphone is required!
 
I don't quite think they're quite good for everyone. People who love LOTS of bass should look elsewhere. I think fans of the Q701 might like them.
 
I consider them comparable in sound almost to my Q701. I couldn't go without the Q701, but I'd be perfectly happy if I just had to use the 8400 as my primary headphone. I think these are a steal at $120. One of the reasons I haven't felt like buying the overpriced SRH-940. I'd have probably bought those if these didn't exist. SRH-940 is nice, but the 8400 I felt was better and much cheaper. I can see how some may prefer the SRH-940 though.
 
I don't think these are super hard to drive but it took me awhile to realize that some portable devices doesn't give them enough volume. What's funny is that on my HD-598 I can't max the Sansa Clip or it's too loud. With the 8400 I HAVE to. These really even benefit from a good DAC. They love my HRT Music Streamer. Based on the E11's sound signature, that should be a perfect match too as an amp. I bet a fairly warm amp would make these sound even better.
 
 

 

[Marximus]

I had issues with the headband as well, and it wasn't really the gap between the cushions that bothered me, but rather the material inside, which is a dense foam (not enough compression, which made it feel hard).  I've had the 8400s on two different occasions, and both times I've modified the headband.  The first time I ripped the whole thing out except the headband frame and put what amounted to a cushion in its place. I cut up a t-shirt and sealed it into a cushion after filling it with polyester fibers which feel similar to down.  The second time I kept the original forms, but cut carefully and removed the foam, then refilled the cavities with poly fibers and sealed them back up with super glue.  Either way, it really adds to the comfort and makes an already-good pair of headphones into great headphones all around.

 

[C.C.S.]

I actually find that they have a decent amount of bass impact. The problem is with background bass parts. Like, if you have one bass guitar with the amp turned to 50, just to quantify the volume, and then you have three electric guitars at 75-100 and a drum kit on top of that, it can be difficult to locate the bass guitar. The bass guitar's higher notes, where it creeps into the mid frequencies are still pretty noticeable but the upper and middle bass registers, where the bass guitar is usually at, wants to hide just a little. It's still there, but you've gotta listen for it a little bit. Other than that, I have no issues with the bass level on these.
 
The only time I notice any sharpness in treble is when the volume is up. Even particularly offensive recordings never get way too bad unless you add just a little more volume to them, at least in my experience. Maybe you have some even harsher recordings than I do. Who knows?
 
And while it's not necessary, I do think that amping these provides enough benefit to justify. I never play these direct from the iPod Classic's HP-out. The bass is a little weird on the iPod and the treble seems like it peaks just a little more often. Might have something to do with output impedance cause the iPod has plenty of power to back these up. I need around three quarters to get these to a strong volume on the iPod. They just don't sound quite as good that way. Even direct from the iPod, though, I'd say these are a tremendous value for the $120-$150 range and I'd still wager that they could rival significantly pricier headphones. They're just that nice. J-Pop, jazz and orchestral, especially, are a treat. The upper mids are absolutely beautiful and make everything come together. And all the detail that you can find in those genres may have you listening to the same album two or three times in a row to try to hear more of the mix.

 

[3wheeledmotion]

The headband comfort issue has me returning them. It really is piercing.

 

[C.C.S.]

Well, that certainly is unfortunate. The headband doesn't bug me all that much as I can make a very slight shift and entirely relieve the pressure. I do that once every hour or two while listening during a long session. During short periods, I don't have to at all. I'm sorry to hear these didn't work out for you. I hope you find something more to your liking.