PerformanceThe performance of the KNS 8400 was judged after they received 100 hours of burn-in on our test rig. For this test we gathered the usual sources and begun our testing. The setups were as follows: Head-Direct HiFiMAN HM-801, Fostex HP-P1, ASUS Xonar Essence One and STX with modified op-amps. The KRK KNS 8400s allow for decent volume straight out of a normal PMP, and iPhone will drive them alright, but in order to unlock their full potential a higher powered source is needed.
MusicThe KNS 8400 headphones are full size circum aural headphones. Their closed back design makes them quite interesting for people on the move who want good sound quality and some noise attenuation. Compared to a set of on-the-ear headphones like the Sennheiser PX 200-IIs which we reviewed a while back the KNS 8400 deliver much more noise attenuation, but it is still nowhere near the attenuation offered by even low end in-ear headphones. Compared to the BeyerDynamic MMX 300s the noise attenuation is similar.
Bass wise the MMX 300s are ahead a little both in terms of power and control at the very lowest octaves, however, the KNS 8400s have a slightly more linear sound to them. Moving up into the midrange and the KNS 8400s begin to show their worth in terms of details. The midrange is very open sounding, however, it does not match the MMX 300's sense of ambience. Positioning is great and the overall detail level is at the same level as the MMX 300. The midrange is more forward in the mix compared to that of the MMX 300. The upper midrange blends into the treble region nicely without any hints of sibilance on well mastered tracks. On poorly mixed pop music they bring out every grueling upper midrange detail and give you the music without toning down any mastering oddities.
Treble performance of the KNS 8400 is very good. It sounds natural and is well extended. Compared to the MMX 300 it is more linear with roughly the same level of extension. Detail wise it is a toss-up between the two, but because of the KNS 8400 having a little more treble it is perceived as being a little more aggressive and perhaps more detailed in the top-end. It is by no means as treble happy as the Head-Direct HiFiMAN HE-300s, nor as bass heavy.
Sound stage wise the KNS 8400 are nothing fantastic compared to Sennheiser HD600 or 650s for that matter, but they can hold their own against a set of headphones like the DT770 and MMX300s from BeyerDynamic. The HiFiMAN HE-300s are ahead on this aspect which I suspect is down to the massively different design of the ear cups and different working principle.
The KRK Systems KNS 8400 leak almost no sound while situated on the head so they can be used on the sub or train without bothering people around you. When compared to the Sennheiser PX 200-IIs the leakage is a somewhat less, sound stage and bass wise the much cheaper Sennheisers do alright, but they lack the layering and the detail of the KNS 8400s.