It's nice how we all prefer different sounding headphones and signatures. My opinion also is that for these you just pick what sound signature you prefer. Both are good. I actually now prefer the 6400 for my music. Of course I LOVE forward mids.
My 6400 has quite good bass and my pair actually has more bass impact than the new 8400. Very slight improvement, but the 8400 I have has more extended bass. It's bass impact is almost non-existent. Bass may improve if you have VERY good clamping force.
The clamping force on my pair is like a 7/10. My old HD-650 was like a 9.5
I just wrote up a short comparison of what i'm hearing. Not a full review, but might be useful for some. Have to cut and paste that next. You probably might not agree with much of it, but who knows!
Overall I think IMO the 8400 is worth the upgrade, but the 6400 is not much worse. Just have to figure out which one has the signature that matches your preferences the most.
That is just so incredibly weird. With my two pairs, the 8400 fantastic bass extension like you mentioned, but there is also a pretty nice amount of bass impact as well. Bass impact and extension far surpass my 6400. When I listen to those after hearing the 8400, the thing that strike me first before the enhanced midrange is the absence of bass. Like, I need to compare it to my AD700...
Agree 100% there. These two are different enough, that it wouldn't make all that sense going straight for the 8400 just because it's a higher model. Both have their unique sound, and their own unique strengths. If it's possible to get both and then send one back/sell, do it! If not, I suggest anyone interested gather as much information as possible before deciding on what you think sounds best.
Here are just a few comments after I listened to these headphones nearly all night. I listened to a ton of music. I even took notes since I'm a nerd I guess. It's a short comparison between the 8400 ($150) and the 6400 ($99).
The 6400 seems to have more bass impact than my 8400. The 8400 extends much lower though. My new 8400 has little bass impact, but the bass is all still there. The 6400 still doesn't have a ton of bass impact, but a little more than the 8400. It's not a huge difference. Drums sounds especially pathetic on the 8400. Try "W.M.A" from Pearl Jam on the 8400 to see what I mean. Despite little bass impact on the 8400, the bass on the 8400 sounds a bit better somehow. It's a lot more clear. I think the 6400 does have more mid-bass perhaps. In comparison they make my DJ100 look like an absolute bass monster and they're not even close to that! The bass on the KRKs is just presented a bit different than most headphones.
The 6400 is more engaging to me and just a lot more fun to listen to for my music. This is because the mids are more forward. The mids on the 8400 to me sound somewhat laid back. It's as if KRK wanted them to be less fatiguing for long durations. I prefer vocals on the 6400.
I haven't decided which is more treble happy. On paper the 8400 is and can be somewhat bothersome. On some music the treble is more fatiguing on the 6400 and on others it's the 8400. There may be some treble peak on the 8400 somewhere, so that could be why it varies. I believe the 8400 has more extended treble though overall. Could be there is a frequency on the 8400 that my ears are really sensitive to.
When it comes to detail the 6400 isn't far behind. On some music there is detail that can't be heard easily on the 8400 (I noticed this a TON and I was very surprised) but is there on the 6400. What's confusing is that on the 8400 with some other tracks there is clearly more detail. This is usually the case when the recording has a large soundstage. It varies between songs. On one song with the 8400 I could not hear a specific background detail until I boosted the mids by 3db, but it was so easy to hear on the 6400. It was..wind.
On the dozens of songs I listened to tonight, the biggest difference for me is that the 8400 has a better soundstage somehow. At times all the background details could be heard easier, especially echos in the recording. The size seems the same.
The absolute biggest difference is that the 8400 is a little more clear. On some songs it's impossible to tell the difference and on others it's super easy. It's the easiest to tell the difference on acoustic music with a large soundstage. We're talking like less than 3-5% more clear, if that. Again, on some (even lossless!) recordings you won't hear a difference.
The 6400 seems better for pop music, rock and female vocals. The 8400 seems to do a little better for classical, soundtracks and non bass heavy electronic music such as ambient. For my music, I prefer the 6400. Except for the bass, this comparison reminds me of the K601 vs the K702! The K601 is more like the 6400 and the K702 more like the 8400. As they say, the K702 is "technically" better, just like the 8400 is when compared to the 6400.
Nice write up! Generally agree except the bass section.
I will absolutely agree and confirm that the 8400 has more soundstage. The 6400 almost tends to bring "everything" more up front, so it's more like a wall of music compared the the 8400's more fan-like presentation. Every time I switched to the 6400 I kept thinking "Grado?" in the way it presents it's sound. I dunno, midrange is almost too close for me! I will continue to test.
I think what the 8400 reminds me most is a tamed (yet superior in many ways) DT990. The 6400 is striking me as a Grado sounding SRH940. Either one shouldn't really be compared to anything else though, because they're both special and very unique in their own ways.