KRK KNS-8400 Professional Monitoring Headphones (Playback 47)

KRK KNS 8400
KRK KNS-8400 Professional Monitoring Headphones (Playback 47)

For many years KRK Systems has been known for its extensive range of near-field monitoring speakers, which are intended for use in both amateur and professional recording applications (visit most any professional music store and you’re likely to see them prominently displayed). More recently, however, KRK has branched out to offer a two-model range of “Professional Monitoring” headphones, with the KNS-8400 ($149.99) serving as the flagship model in the line.

How successful is the KNS-8400 as a monitoring headphone? We’ll come to that point in a moment, but before we do we need look at an even more fundamental question: namely, what exactly is a “monitoring headphone” supposed to do? My practical experience is that almost all manufacturers of monitoring-oriented speakers and headphones will use fairly similar adjectives to describe their products. No matter which monitoring product is being portrayed, you can expect to hear descriptive terms such as “accurate,” “natural,” “faithful,” “revealing,” “honest,” etc. But while the terms used to describe self-proclaimed monitoring products tend to be quite similar, the sound of those products can and does differ, sometimes substantially. How can that be?

The answer, I think, involves the fact that there are (at least) two overlapping but not identical schools of thought regarding what monitors should be and do. One school of thought holds that monitors should be precisely accurate and highly transparent mirrors that exactly reflect the sonic characteristics of recordings—which implies that the products should have, as a minimum, neutral and extremely evenly balanced tonal response.

Another school of thought, however, holds that monitors should ideally make it easy for recording engineers to hear minute variations in textures, timbres, and resolution within recordings. An often unspoken expectation is that monitoring devices will do a particularly good job of exposing sonic variations that fall in frequency bands where problems, if any, would be most noticeable or annoying later on. You can hear some of this emphasis in a KRK positioning statement for the KNS-8400, which states, “After all, hearing what is wrong with your mix is just as important as hearing what is right!”

While these two schools of thought aren’t necessarily mutually incompatible, they do tend to lead listeners to focus on different priorities. My sense is that adherents to the former school of thought place a premium on monitors that, first and foremost, offer dead-neutral tonal balance, though other performance factors are of course also important. In contrast, adherents to the latter school of thought may be willing to accept minor variations and tradeoffs in tonal balance, provided that their monitors meet the primary requirement of helping listeners quickly identify (and then presumably fix) flaws in the recording.

With these background observations in mind, let me offer the initial assessment that KRK’s KNS-8400 is geared more to please those in the “find and fix sonic flaws” camp, and less to please those in the “neutral tonal balance comes first” camp. As you might expect, this is an apparent design choice that has some far-reaching sonic implications, as we’ll discuss in a moment.


  • Closed-back design: The KNS-8400 is a closed-back, circumaural headphone whose ear cups feature special foam pads said to provide “high noise isolation for both noise rejection and (to prevent) leakage.” KRK goes on to state (without supplying much in the way of specific details) that the KNS-8400 features a “newly developed headphone acoustical system bringing a new level of headphone performance for the first time.”
  • Durable, lightweight construction: The KNS-8400 features ear cups made of “durable, impact resistant materials throughout,” and that promise “lightweight construction for use over long sessions.”
  • Driver technology: The KNS-8400 features drivers with relatively large, 40mm diaphragms and that features motor assemblies that incorporate “high-efficiency Neodymium” magnets. KRK ambitiously promises a number of benefits for these drive units, including:
    • “Exceedingly accurate, natural and wide frequency response.”
    • “Large dynamic range with consistent low-distortion detail and clarity.”
    • “Extended low frequency definition.”
    • “Transparent reproduction of high frequencies, resulting in highly accurate imaging."
  • Accessories/Convenience/Ease of Use: The KNS-8400 offers a number of convenience- and/or performance-oriented accessories including:
    • A user replaceable, single-sided, straight signal cable featuring oxygen-free copper conductors. The clever plug mechanism through which the cable attached to the headphone is extremely easy to use and appears quite durable.
    • User replaceable headband and ear cup pads.
    • An adapter cable that incorporates an inline, slider-type volume control.
    • A soft carrying case.
    • Anti microbial/bacterial cleaning cloth.
    • Gold-plated ¼” jack plug that unscrews to reveal a 1/8” mini-jack plug. 
    • Ear cups that swivel, adjust, and can be folded flat for transport.


In terms of sonic character we found the KNS-8400 to be a mixed bag. On the plus side of the ledger, the headphone offers admirable and impressive levels of clarity and detail for its price. It also offers bass that is quite deeply extended and very well defined. On the downside of the ledger, there is the fact that the tonal balance of the headphone seems skewed in a midrange-forward direction with particular energy in what some might call the “presence” region; that is, the upper midrange band where mids transition into highs.

Another potential way of looking at this balancing scheme is to say that bass (and perhaps the lowest of lower midrange frequencies) are quite good sounding in their own right, but shelved downward in level relative to the broad middle of the midrange that the KNS-8400 provides. Either way you look at things, either as the KNS-8400 having forward-sounding mids or somewhat recessed bass, there are several practical implications of this balancing scheme.

First, midrange details in general, and upper midrange details in particular sound remarkably clear and easy to pick out from within the mix. Frankly, I have observed this same general characteristic in some of the monitoring loudspeakers I have heard in recording studio control rooms, so that it seems that KRK is right in making the claim that the KNS-8400 is balanced much like (some) other high quality monitoring devices.

Second, bass, when heard in isolation, sounds taut and, when the music calls for it, quite deeply extended. Low frequency pitch definition is quite good, too, especially in light of the headphone’s modest price. These qualities are all to the good.

The trouble, though, is that the KNS-8400 does not give an entirely accurate view of the overall tonal balance of good recordings (or if it does, then a great many high-end loudspeakers and headphones have got things wrong, which I doubt). Thus, mids and upper mids sound pressed forward, while bass—though capable of great depth—seems lacking, at least relative to the midrange, in weight, power, and punch. These points of emphasis (or de-emphasis, as the case may be) are subtle enough that the KNS-8400 can be and is enjoyable for music listening, assuming its voicing fits your musical tastes. But it also means that—if you are used to listening to familiar recordings through high-end transducers—the general shape and balance of mixes may seem a little bit “off.”

These qualities mean that while the KNS-8400 makes it easy to focus on potential sonic problems in the midrange and upper midrange, which is precisely the area where the most obvious problems in recordings are likely to crop up, it doesn’t really give you a clear picture of how mixes are balanced. In practice, I think this means the KNS-8400 might be more useful for monitoring the recording process—especially when capturing vocal or other midrange-centered tracks, but less reliable for mixing (where you really would want to know exactly how the mix is balanced from top to bottom).


For purposes of illustrating some of my comments above, let me draw two examples from Reference Recordings excellent Jazz Kaleidoscope compilation album. The first is the Mike Garson Quartet’s performance of “Nothin’ To Do Blues.” The track opens with just the sound of a piano, brushes on a snare drum, and Brian Bromberg’s bass. Through the KRK’s, the “swish” of the brushes on the snare sound crystal clear, the piano sounds beautifully articulate and expressive, but the bass sounds out of character, with less weight on mid-bass frequencies than it would normally have, and more emphasis on midrange accents, fingering noises and percussive (string-on-fingerboard) sounds than would usually be the case. Mike Garson’s piano solo sounds lovely, though a bit up-turned in the upper midrange, and thus prone to a slightly “pingy” sound. Later, when Brian Bromberg takes his solo, his bass manages to sound fascinating through the KRK’s, yet not quite right. Bromberg’s flashing fingering techniques and midrange accents are, to a degree, spotlighted by the KNS-8400, but middle and lower register of the bass lack their usual degree of weight and power (though their sheer depth is properly shown). Let me emphasize that there’s no problem with bass extension (it goes plenty deep); instead, the difficulty is that bass is pulled back in the mix relative to mids and upper mids.

Next, let’s listen to “O Vazio” from the Jim Brock Ensemble. The track opens with a delicious mix of low and middle frequency percussion instruments played off against one another. Then, at about 40 seconds in to the track an extremely powerful low bass drum is struck. As I listened to the opening minute or so of the track, the KRK’s strengths and drawbacks were presented in stark contrast. The open percussion notes sounded for the most part terrific—clear, delicate, and articulate with plenty of inner detail. The lower percussion at first sounded good, too, though perhaps a bit down on “oomph.” But when the really big bass drum came along, things went off track. That drum should be almost overpowering when it is first struck, but through the KRK’s a drum that should sound like real thunder instead sounded like, well, comparatively distant thunder. Later, as more midrange instruments join the mix, I was struck by how midrange timbres were pushed forward to a point where they sometimes took on a subtle steely edge that, while increasing perceived clarity in a sense, had the effect of making some instruments sound “overstated” and thus not quite natural.


Consider this headphone if: you want a relatively low-cost headphone that could be useful for monitoring recordings in the making, and that offers a very high degree of articulacy and clarity for the money. Consider this headphone if you favor transducers with a slightly midrange-forward tonal balance.

Look further if: you prize headphones with strictly neutral tonal balance; there are others in or near this price class that do better in this respect.

Ratings (relative to comparably priced headphones):

Tonal Balance: 7
Clarity: 9
Dynamics: 8.5
Comfort/Fit: 8
Sensitivity: 9
Noise Isolation: 9
Value: 8


The KRK KNS-8400 does many things well and offers very high degrees of clarity, detail and definition for the money. One drawback, however, is that the headphone offers a midrange-forward sound, with particular emphasis in the upper midrange region, which can make bass seem as if it is shelved downward somewhat in level, at least by comparison to the midrange.


KRK Systems KNS 8400 Professional Monitoring Headphones
Frequency Response: 5Hz – 23kHz
Drivers: 40mm aperture drivers
Sensitivity: 97dB/1mW
Impedance: 36 Ohms
Weight: 8 oz.
Warranty: Three years, parts and labor
Price: $149.99

KRK Systems, LLC.
(954) 949-9600 Option 1, Sales; Option 3, Support)

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