KRK KNS-6400 Review - Impressive $99 Giant Killer
Jun 29, 2011 at 10:00 PM Thread Starter Post #1 of 235

tdockweiler

Headphoneus Supremus
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This is a review of one of my favorite headphones. I've been using it for quite awhile and love it. KRK seems to have gotten nearly everything right with this headphone. I'd feel really bad if I didn't review such a great (and severely overlooked) headphone. This time around I'm not going to over-analyze everything and these are basically just some impressions and comments. It's a bit all over the place, so feel free to skip down to the "TL ; DR" edition if you don't want to read my rambling.

Late last year I bought the KRK KNS-8400 and posted a positive review of them. I liked them a lot despite them not having my favorite signature. It was one of the very few headphones I didn't immediately like and it needed about three days of burn-in to sound good and to smooth out it's treble. I ended up selling it because I rarely used any closed headphones and  I had so many open headphones at the time. I was so impressed with it when I had it that I even went out and bought another Shure SRH-840 just to compare them! The SRH-840 lost.

I was curious about the KRK KNS-6400 after seeing it's frequency graphs and took a chance at my local Guitar Center. It was a risk because my location didn't accept any returns. They run about $99. I imagined there would be a huge drop in sound quality with the step down. Was I ever wrong!

I got them home and immediately liked them and was quite impressed. They didn't need ANY burn-in AT ALL to sound good! My first KRK KNS-8400 needed about three days.

OK, this may sound silly, but all my music sounds exactly how I always remembered it. Is that a bad thing? There are songs I've listened to hundreds of times and they sound like how they should. These things don't really alter the music much and try to make it better than it really is. Despite this, they're not boring and music is still engaging and fun to listen to on them. Generally some studio monitors can be a snore fest, but not these.

I don't think they're perfectly neutral (but what headphone is? My K601 sure seems like it), but close enough for me. If anything, there may be a VERY slight boost in the mids somewhere. Notice I said SLIGHTLY. I don't really think they should be put into the group of headphones with forward mids like the DJ100, ATH-AD2000 and HD-598. The mids are just quite engaging and even more so than the KRK KNS-8400, or so it seems. I'd have to compare them side by side.

I've been listening to these so much since I got them that I now have a good feeling of how they're supposed to sound. Sometimes they sound like garbage and other times very, very impressive. Why? Well, it all depends on the recording. A few weeks ago I switched from another headphone and put these on and I remember thinking "Not so clear..." I got the wrong impression that it was the headphone, but it's absolutely NOT. It's the recording. Even some of my lossless tracks sound like garbage. The other headphone just wasn't as revealing of how bad the song was. I don't buy a lot of stuff on Itunes, but it's easy to tell which tracks are downloaded from Itunes! I sure wish it was easier to buy on CD some of my favorite ambient music. They're revealing, but not overkill. If you normally hate studio monitors, give these a try.

I haven't compared the two KRK headphones side by side, but the KRK KNS-6400 sounds more natural than the KRK KNS-8400. It should be a better match perhaps for those that just want to enjoy their music and not analyze it 100% of the time. The 8400 is the one that seems to have the more extended treble. The difference between the two is kind of like the difference between the K601 and K702 kind of. The K702 has some similarities to the KRK KNS-8400!

The part I don't get is that when I listened to the KRK KNS-6400 I immediately noticed that it gave me the feeling of more bass than the 8400. The bass had more impact, when I almost never got this impression with the 8400. At times I questioned if my 8400 was a lemon, but everything else was fine. I don't know if KRK made any changes in the models, but it's possible. I always said that the HD-598 had a smooth sounding signature (despite the forward mids!), but this 6400 is even smoother! Nothing jumps out at you and will annoy your ears. To me, it's just an enjoyable studio monitor that won't bore you to death. In my HD-598 review I said that if I were to describe it with one word, it'd be "Smooth". For the KNS-6400, it'd be "Accurate". All my music is exactly how it should be.

I did say that the headphone doesn't change the music. OK, maybe a tad. One thing I've noticed is that on some very brightly recorded and harsh tracks, they're made a little more bearable on the KRK KNS-6400 compared to the 8400. I guess it seems to tame them just very slightly. On the K702, DT-880 and even the KRK KNS-8400 it didn't touch them at all ever. I have no problem with the 6400 doing this very slightly. Some many not agree with what I'm saying. Many people seem to think it's the headphones fault for all the harsh sounding songs, when it's just the recording itself. I have about a dozen songs from a Japanese singer named Hitomi that just about annoy me on nearly any headphone due to how they're recorded. It got so bad I just removed from my collection.

Another very strange thing I noticed is that the KRK KNS-6400 has a very impressive soundstage for a closed headphone! I felt that my Koss Pro DJ 100 had one of the best (under $200 closed), but this may have that beat! At times I'm even fooled into thinking I have an open headphone! I don't EVER recall this with my KRK KNS-8400 and originally I complained that the 8400 had just an OK soundstage. One thing that could help is that the KRK KNS-6400 drivers seem to be angled!! Nice going KRK! Of course it all depends on the recording. Some CDs with nothing but nature sounds feel as if I'm actually caught in a real life thunderstorm with the rain all around me. Speaking of that, these things are so nice for ambient music such as Helios. With movies I sometimes forget I have a closed headphone on my head.

On the first day I found them fairly uncomfortable. It seems that they need some time to adjust to your ears. I stretched out the pads slightly and the problem went away. By the time the problem was fixed I had already ordered the 8400's memory foam pads. The KNS-8400 memory foam pads fit on the 6400!

I'll just come out and say it that the 8400 and 6400 (with memory foam pads) are some of the most comfortable headphones ever made. The only negative for me is that my on my head, the headband seems to extend 1 1/2 inches on each side. They look a big goofy on my head. I tried and failed to use these during weight lifting (at home!). That's too bad. They're secure on my head, but using them during the bench press is probably asking too much! People with bigger heads will love the fit I think. I could probably wear these  all day without any pain.

I always said that the KRK KNS-8400 was one of the clearest sounding headphones I've ever heard. You'd think that since the 6400 costs $50 less there would be a massive drop in sound clarity or overall sound. Not really. I don't really feel like the sound clarity drops much. Still crystal clear. I think on the KNS-8400 there is more treble extension. I'm not sure what else. I'd have to compare them side by side again. I most definitely prefer the mids on the KNS-6400.

Other than the soundstage and sound clarity, the next best thing about the KNS-6400 is the detail! I could call this thing a detail monster with no problem. It has more detail than the K601, K702, DJ100, MDR-V6, Sextett, K240 Studio and basically many others I've tried. I've done numerous side by side comparisons. There is this song I often use for reference that has 5 metallic sounds on the left that are very, very faint. On the HD-650 I had I could only hear about 3 of them, but only if I EQ down the bass. Yes, really. On the KRK KNS-6400 I hear 5 or 6 clear as a bell. Quite impressive. Basically if you want to hear everything that's in a recording for cheap, this will do the trick. I always thought maybe that the more you spend, the more detail you'd be able to hear, but price doesn't seem to mean much when it comes to this. Sometimes. The KRK KNS-8400 already beat out my Shure SRH-840 in nearly every area, so I guess now I'll need to compare the KRK headphones to the Shure SRH-940. I bet they can hold up fairly well! Maybe not.

For probably a year I was always looking for a headphone that could dethrone my DJ100 as my favorite "fun" headphone. This just might be it. The DJ100 is still addicting and needs an amp and this doesn't. It sounds perfectly OK straight out of my Ipod Touch.

You know what? I hate the dozens of PERFECT reviews where people are afraid of pointing out negatives of their favorite headphones. I hate it, but as it is right now and with weeks of listening, the KRK KNS-6400 is about as perfect as you can get. It's one negative is that I still hate it's cable. It seems to be very durable, but still yet seems to tangle up so easily and you can hear it move around when the headphones are not in use, but over your ears. It's too bad it would be nearly impossible to recable these. I may just buy the coiled cable. I'm sure the wiring inside is something high quality, but it's really one of the most annoying cables there is. You could also wrap it around something and when unraveled it'll probably retain that shape for a day. I bet I could run over it with my car and it'll still be working though.

One nice thing about this headphone also, is that it may be the perfect closed competitive gaming headphone! It has some great imaging, a good soundstage, tons of detail and isn't super bass heavy. Not bass light or even close. I don't like closed headphones for gaming, but if I did need one, this would be it.

TL;DR Edition

PLUS:

Accurate Bass, Good Mids, Fairly unforgiving, Tons of detail, Comfort, Sound clarity, Imaging, Very good soundstage for being closed!, Smooth treble and overall sound signature, Good for nearly every genre, Accurate, No excessive clamping force, Great price ($99!), Angled drivers, Non-fatiguing, Amazing for female vocals (especially Jpop/Cantopop)

MINUS:

Cable is annoying. Pads are kind of tricky to replace (maybe I'm doing it wrong).

So far these are the best unamped closed headphones I've heard yet under $200. Ever since getting these I've rarely used my K601 and HD-598. Something about how they sound makes me keep going back to them. The HD-598 is more fun to listen to, but doesn't quite sound as clear sometimes, but is more forgiving. Less detailed for sure.

Now I guess this will be what I'll be using until I find something better. Perhaps the Shure SRH-940? Who knows.

For $99, this headphone is a steal. I think it's safe to say I prefer it to the KRK KNS-8400! Sadly, few people on here seem to want to bother trying headphones that few people have heard. The KRKs and Koss Pro DJ100 are severely under-appreciated headphones. Sometimes all these inexpensive headphones make me wonder why I bother with $300+ headphones. If I had to only use the KRK KNS-6400 as my primary headphone, I'd be perfectly satisfied.
 
 
Jun 30, 2011 at 8:58 PM Post #2 of 235
Thought I'd add a picture of the 6400. People love pics.

 
Jun 30, 2011 at 10:01 PM Post #3 of 235
Very nice write up! I always love reading reviews for headphones that are severely underrated or go completely unnoticed. It's refreshing.
 
Quick question about the headband material between the two, does only the 8400 have a memory foam headband or does the 6400 have it too?
 
Glad to see it uses the same headband design as the HD650. Why don't more companies use this? It's obviously the king of the hill when it comes to comfort.
 
Jun 30, 2011 at 10:13 PM Post #4 of 235


Quote:
Very nice write up! I always love reading reviews for headphones that are severely underrated or go completely unnoticed. It's refreshing.
 
Quick question about the headband material between the two, does only the 8400 have a memory foam headband or does the 6400 have it too?
 
Glad to see it uses the same headband design as the HD650. Why don't more companies use this? It's obviously the king of the hill when it comes to comfort.


Thanks, I was wondering if anyone was ever going to read this "review"
normal_smile%20.gif
. It's kind of a big wall of text!
The KRK KNS-6400 uses a different material for the head band than the 8400. It's a cheaper type of foam and when you press down on it it doesn't take a few seconds to come back, like the 8400's memory foam. The 8400 used memory foam on the pads and on the head band.
 
The head band on the 6400 is comfortable, so I have no problems with it. The good news is that you can actually buy a replacement head band (just the padding) for the 8400 and use it on the 6400. I'm about 98% sure they're the same size. I haven't felt the need to buy the memory foam head band...yet. These have been on my head the most lately. Due to it's soundstage, lately I've had no huge need to use my open headphones all that much for music. Sometime I'd like to try the Shure SRH-940 if they ever come down in price. I don't think they could possibly match the comfort of the KRK headphones.
 
Here's one of the KRK KNS-8400. Very similar design as the 6400, but with memory foam. I love the memory foam pads:
 

 
Here's a frequency graph:
 

 
 
 
 
Jun 30, 2011 at 10:47 PM Post #6 of 235


Quote:
Great review tdockweiler!! How's the isolation on the 6400's? Looks like it could be pretty damn good. 


Isolation is just average for me. The problem with them for me is that I have a smaller head I think, so there isn't a ton of clamping force.
I imagine the isolation would be a lot better for those with a larger/wider head.
 
Here's a chart I found. Sorry, I love charts:
 

 
 
Jun 30, 2011 at 10:52 PM Post #7 of 235
Quote:
The head band on the 6400 is comfortable, so I have no problems with it. The good news is that you can actually buy a replacement head band (just the padding) for the 8400 and use it on the 6400. I'm about 98% sure they're the same size. I haven't felt the need to buy the memory foam head band...yet. These have been on my head the most lately. Due to it's soundstage, lately I've had no huge need to use my open headphones all that much for music. Sometime I'd like to try the Shure SRH-940 if they ever come down in price. I don't think they could possibly match the comfort of the KRK headphones.


Yeah, I guess you really wouldn't need a memory foam headband as much as you would need it for the earpads. As long as it's comfortable as is.
 
I would really love you to sometime. SRH940 is the 2nd best headphone I've heard, in in tangible language, the best. Bass is lacking, yet still sounds good with mellower music, but I'm always still craving a bit more from the bottom end. Luckily my Sony E354 gives me a little lower end response than my iAudio 7, but still cannot be considered up to my standards. So much good to say about the sound drops off suddenly when we talk about the comfort. You are 100% correct when you say they couldn't possibly match in comfort, because very few headphones I've tried rate lower. Headband lasts about 45 minutes to an hour if I'm lucky, and my ears get irritated anywhere from 20 minutes to half an hour, after being pressed on the inside of the cup. Great, great sound, but much lacking in comfort. (I'm pretty amazingly picky when it comes to comfort, so for many, these would probably be just fine. But the 6400's *definitely* look more comfortable).
 
 
Jul 23, 2011 at 2:07 AM Post #9 of 235
Dunno, kinda curious about these now...
 
And we all know I couldn't decide between them, so I'd just have to buy both.
 
EDIT: In fact, I'm moments away from cancelling my Z1000 to get both of these instead. Hmm. What to do.
 
Jul 23, 2011 at 5:59 PM Post #11 of 235
Still have the 940 to compare them to? Probably not, but it'd be an interesting comparison. The KRKs could probably compete quite well with the 940 in some areas.
I'm very curious if the 6400 has a better soundstage than the Shure SRH-940.
 
As you know, I prefer the KNS-6400 due to it's more natural sound, but the 8400 would be better as a plain studio monitor maybe. My 8400 was VERY treble happy, just like my K702.
For my music preferences the 6400 was a better match. I wonder if KRK made some minor changes (improvements) to the 8400. Mine was an early pair and I got them before most websites had them available.
My 8400 needed 3 days of burn-in to tame the painful treble. The 6400 needed ZERO burn-in and I never had that issue.
 
The 6400 takes about one day to adjust to your ears. I know this sounds weird. I stretched my pads a tad, but I didn't really need to do this. By the time I ordered the 8400 memory foam pads they were already very comfortable.
 
Right now I'm off to try the 6400 more with gaming. I haven't used them much for gaming yet.
 
BTW if you don't have a small head, there will be more clamping pressure and better bass. For me there is not a lot of clamping force, which I like. The bass on these is so different than many other headphones. It's pretty accurate based on the recording. Based on graphs it looks like the KRK KNS-6400 has better bass extension than the SRH-940. Can't trust graphs though.
 
Do you have a "Guitar Center" in your area that accepts returns? That may be one option. They're just as cheap locally as online.
 
Jul 23, 2011 at 6:32 PM Post #12 of 235
Well, about the big head question, yes, I have a reasonably big head. The AT AD series fits me like a dream.
 
But more importantly, a status update. Surprisingly, I "Requested Cancellation" on Amazon for my Z1000, and this is the first time they said they weren't able to. So yes, I will in fact be getting the Z1000. But, I couldn't resist, and also ordered the 6400 and the 8400. Now, if only I still had my SRH940, I could do a 4 way shootout, or at least do a SRH940 vs Z1000 or 6400 vs 6800. Oh well, I hope my memory serves me well, I listened to those quite a bit.
 
Jul 25, 2011 at 8:54 PM Post #13 of 235
I had decided on the Audio Technica M-50 but after  reading this thread I'm thinking about the KNS 6400. I'm now using the AKG 701, and the open phone realy,realy bothers others around me. I also find that the bass is thin on the 701 and they are too analytical and I get listening fatigue using them.  Im using a doge tube headphone amp and using FLAC files through a stand alone   DAC. I also have a momba portable amp for my sanza fuze. So  my question is which closed headphone the Audio Technica M-50 or the KNS 6400 would be most likely to keep me happy (for a while,anyhow)? Is there a different closedphone that would be better?
I listen to electronica,female jazz and some music from the 70's (Pink Floyd ect.)
 
thanks Bri
 
Jul 25, 2011 at 9:58 PM Post #15 of 235
Quote:
The bass on these is so different than many other headphones. It's pretty accurate based on the recording. Based on graphs it looks like the KRK KNS-6400 has better bass extension than the SRH-940. Can't trust graphs though.

For sure, especially with how screwy the 8400s measured.
 
Looks like they got a weird pair of 6400s too or messed up measuring them, look at the channel imbalance:
 

 
@ Katun Awesome!
 

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