KRK Systems KNS-8400 Closed Back Over-Ear Studio Monitor Headphones Long-Term Review @
By: Michael Phrakaysone

For nine-years that ModSynergy has been on the Internet, our audio review segment has grown from  babyhood to adulthood.  We've reviewed and seen many different items throughout the years, starting back to when the MP3 player was starting to take off.  Just looking back at some of the early reviews that were done, and to see the progression that was made, perspectives change on thoughts that were once held.  Some of the stuff that were thought to be good back in the day, isn't exactly the case in present mid 2012. Audio products and audio preference is like that.  Audio is like a fine wine because with age, it gets better, and with age our taste begins to change.

I’ve been fortunate enough that I’ve had my fair share of audio reviews on this website and I’ve learned much about the evolution of finding true audio excellence.  When it comes down to it, the most basic way I can explain what it means to experience true high-quality sound is this. Any music or movie that is being presented to you should be given to you the way they were originally intended to be, without any type of modification of the sound.  What this means is that one needs to find a solution that is balanced and fair between the frequency ranges (low, mid and high).  One range cannot be favored over the other. This is a good baseline to seek, and once found, you will not want to go back to anything less.

HD, or high-definition, is a marketing term that is thrown around the industry far too frequently it seems. Some manufactures have taken advantage of the slogan and regrettably have tarnished what it means in the process.  Some manufactures have used this slogan on their audio gear and customers are instantaneously drawn to it thinking its excellent.  What I advocate is investing in two things.  Invest in your source; audio will only be as good as where and what it’s coming from.  Invest in your speakers or headphones; picking right the first time will prevent you from needing anything else in the future.  Once you have established an audio source, the speakers or headphones you opt for will perform to its fullest potential.

KRK Systems is a renowned and premier player in the audio industry and was founded in 1986, by Keith Klawitter. He had been an engineer for years working on such films as "Brainstorm" and "The Doors". Frustrated by the fact he couldn't find a monitor that gave him clarity and accuracy, he began building his own monitors. Other engineers and producers began to take notice of Keith's high-end studio monitors, a groundswell began and a company was born. They also began commissioning him to build custom main systems as well. We attribute this remarkable beginning to Keith's affinity for electronics, his passion for music, and his originality and insight.

KRK Systems is a company that caters to musicians and audio professionals through such items as the Studio Monitor, Subwoofers, Headphones, and Enhanced Room Geometry Optimization system.  I’ve been lucky to have reviewed the M-Audio AV40’s and it was the one that introduced me to a out of the ordinary breed of speakers, in this case called ‘monitors’.  If you haven’t read the review of these little wonders, please check it out.

Something different that ModSynergy pays attention to is long term reviews.  In a normal review, one would have only a few days or few weeks to spend with a particular item meaning it won't be used on a regular basis.  Most things can pass initial quality but reviewing something long-term is different.  It allows the reviewer to monitor how the item will hold up to everyday usage, if any troubles arise over time that a normal review cannot reveal.  For example, let's say one reviews a speaker system and its fine initially, but what happens if 6-months down the road a thump sound starts to form once powering down the unit that you’ve never heard before?  This could be a sign of a problem.

Today I will be providing a long-term review on a different beast.  We've already looked at studio monitors, but those are stationary and cannot be lugged around.  What about if you want a portable solution to studio monitors when you're on the go?  Today you will be reading the review of KRK's flagship headphone offering with their KNS-8400 Closed Back Studio Monitor Headphones.  Read on to see how this reference quality 40mm driver closed-back headphones perform and holds up.  Are they really like having studio monitors on your head?  Will this be your next investment?

About KRK Systems

Great sound doesn't start with the studio, the microphone or the latest wiz-bang sampling device. It starts in the heart, and it starts with the truth...the very essence of the KRK design philosophy. This is why we come to work every day. To deliver products that are true to the legacy that KRK was founded on.

When we design a studio monitor we always start with the question "what does the customer really want from their monitor?" The usual terms get thrown around like accuracy, reliability, precision, and many more marketing buzzwords. Important words about what the product should be...but not necessarily speaking to what users really need. A product they can trust! Engineers and Artists need products they can put their faith in. Ones that deliver a true acoustic interpretation of the mix. Sounds Simple...but it isn't so simple when it comes to these complex designs.

At KRK we take design and performance very seriously. If it's not won't go to market...period! That is the kind dedication we pour into every product. And we do that because we know our customers have come to trust us for that. We know they are dedicated to their music and the products they use deserve the same design dedication. This "design first" mentality is what the company was founded on and has helped KRK become an industry leader in this highly specialized market.

KRK Systems KNS-8400 Product Overview

KRK Headphones provide a precise listening experience that takes you from personal studio to commercial studio to on-the-go track evaluations -- and they allow you to accurately enjoy your music with the consistent voicing philosophy and honest reproduction top producers, studio musicians, performers and engineers have come to trust. KRK headphones provide incredibly natural frequency response that gives you a reference standard unaffected by your location. Day or night. Studio or home. Without disturbing others. Without compromising your tracks. Passionate about music and interested in experiencing the artist's vision as it was intended to be heard? Then experience KRK.

Headphones for Educated Ears.
Looking for a pair of headphones that are specifically designed to replicate music as it should be heard with the ability to satisfy experienced ears? Get your head around this: KRK has always been focused solely on accurate monitoring. The KNS 8400 -- with their ability to reveal exactly what you have on the tracks is an ideal choice for critical listening. Being able to discern the most subtle differences in pitch, timbre and tone helps you to get it right every mix, every take, every performance. Isolating memory foam in the ear cushions delivers improved low end response and because they gently conform to your unique head shape you'll be comfortable wearing them all day.



  • Accurate, natural and wide frequency response
  • Class leading KRK sound clarity, very low-distortion
  • Precise Imaging and extended LF response
  • High isolation for both noise rejection and leakage


  • Detachable and replaceable locking cable
  • Rotating ear cups for travel and storage
  • Durable, impact resistant materials throughout
  • Replaceable ear and head cushions


  • Lightweight construction for use over long sessions
  • Adjustable low-pressure headband system
  • Ear and head cushions utilize advanced memory foam
  • Self-aligning yoke system ensures the best possible fit

KRK Systems KNS-8400 Product Features

  • Voiced to remain true to the character of KRK's class leading studio monitors, developed with 25 years of years of experience in studio sound.
  • The latest reference quality frequency response for closed-back, circum-aural dynamic headphones.
  • Newly developed headphone acoustical system bringing a new level of headphone performance for the first time.
  • Utilizing the latest in acoustic foam technology ensures class leading performance in both reproduction and isolation.
  • A new standard in headphone comfort, even over extended periods of use, designed to avoid feeling uncomfortable during long sessions. The special foam conforms to the ear to help ensure an improved fit.
  • Exceedingly accurate, natural and wide frequency response.
  • Large dynamic range with extremely consistent low-distortion detail and clarity.
  • Extended low frequency definition, ensures the bass component of your music is accurately reproduced, and is not lost.
  • Transparent reproduction of high-frequencies, resulting in highly accurate imaging.
  • High-efficiency Neodymium 40mm driver.
  • High durability 2.5m single-sided straight cable with oxygen-free copper wires.
  • Adjustable, foldable driver enclosures provide comfort and portability.
  • Replaceable cable, head, and ear cushions to ensure long product life.
  • Soft carrying case embossed with the KRK logo for travelling engineers, or storage when not in use.
  • 1/4" jack plug can be unscrewed to reveal a 1/8" plug for laptops and portable media players.

KRK Systems KNS-8400 Product Specifications

  • Configuration: Closed back, circumaural
  • System type: Monitor Headphones
  • Cable: 2.5 m, (8.2 ft.), 99.99% OFC detachable
  • Ear Cushion type: Acoustic memory foam [KNS-8400]
  • Headpad Finish: Premium leatherette [KNS-8400]
  • Nominal Headband Pressure: 4 N (based on average head size)
  • Ambient Noise Isolation: up to 30 dBA [KNS-8400]
  • Transducer: 40mm, neodymium
  • Power Handling Full Range: 1000mW
  • Nominal Impedance: 36 ohms
  • Frequency Response: 5Hz to 23 kHz
  • Sensitivity (1mW): 97 dB SPL
  • Calculated Max SPL: 124 dB SPL
  • Connector: Gold-plated stereo 1/8" (3.5 mm)
  • Volume Control: in cord, detachable
  • Finish: Black impact resistant plastic
  • Dimensions: 3.7" (94mm) x 10.5" (267mm) x 9.6" (244mm)
  • Weight: 0.5 Lbs. (0.23Kg)

First Impressions

KRK Systems

The KRK Systems KNS-8400 that I am reviewing today was ordered directly from KRK Systems themselves and represents the retail look you would be able to locate in stores.  A plastic tab is slotted on top of the box to have it easily hang on store shelves.

The KNS-8400 comes packaged in a very stylish corrugated box.  I love the color scheme KRK decided to choose for their headphone (it resembles the colors chosen for ModSynergy), the black and yellow color just pop out on the smooth feeling package.  The whole design of the package and the way its laid out is classy and professional.  Kudos to the folks who contributed to the package, I think they have done a great job.

The front of the box contains an image of the headphone along with two key features mentioning the volume control that is included with the package and that the KNS-8400 can offer listeners up to 30 decibels of noise isolation from ambient noise. 

The rear of the box contains the overview and product features of the KNS-8400, while the side contains a list of specifications regarding the headphones and contents that are included.

What's Included

  • KRK Systems KNS-8400 headphones
  • Connection cable, with screw-in adaptor (fitted)
  • Protective soft bag
  • Anti-Microbial/Bacterial cleaning cloth
  • Detachable/Replaceable sleek profile in-line high quality volume control
  • User Manual
  • Luxury grade leatherette ear and head cushions
  • High grade aluminum dampening plate and logo on earcups

Purchasing the KRK Systems KNS-8400 headphones, you get a very nice bundle for around $150CDN.  Aside from the headphones, you are given a screw-on gold plated 1/8" to 1/4" stereo adapter that has been fitted onto the detachable/replaceable connection cable, you get cleaning cloth (looks the same ones you get with monitors, looks microfiber), a nice looking protective soft bag embossed with the KRK logo that will protect the KNS-8400 from dust and the elements while travelling or when not in use, and a user manual.

What type of applications will the KRK Systems KNS-8400 be used for?

The KNS series headphones are designed for critical listening and monitoring in the following situations:

  • Engineer/Artist Recording Studio: Mixing/Monitoring/Recording
  • Engineer/Artist Broadcast Studio: Mixing/Monitoring/Recording
  • Musician/Artist Studio: Monitoring/Composition/Recording
  • Musician/Artist Live/Stage, Monitoring
  • Technician Monitoring at any location
  • General Personal music listening

As of this written piece, the KRK Systems KNS-8400 can be found for $150 Canadian and $135.79 American through, which makes it an attractive and affordable solution for portable headgear. 

Replaceable Parts

The differentiating factor with the KNS-8400 is that it has many parts that can be replaced over its lifetime.  Items such as the detachable cord, in-line volume control, head, and ear cushions can be replaced.  What this means is that because parts are replaceable, the KNS-8400 can have a longer product life than normal headphones, so in like 5 years if a cord goes bad, you can just replace it with a new one instead of going out and having buy new pair of headphones.

Visual Overview

The KRK Systems KNS-8400 is touted as portable studio monitors for your ears and is capable of folding 90-degrees assisting with its portability.  They are full size headphones that completely surround the ear.  The headphone is also adjustable for comfort on all sizes and shapes of heads they will be on because comfort is taken care of on the KNS-8400 with its utilization of acoustic memory foam cushions for your ears and for the headband. 

The KNS-8400 comes exclusively in black matte, no other color choices are available.  The KNS-8400 doesn't choose to be a standout like the 'hyped' Beats by Dre branded products, but it feels natural in its own skin.  The headphones are surprisingly lightweight coming in at 0.5 Lbs and doesn't give much added weight to your head.

The KRK Systems KNS-8400 comes in closed back form meaning sound isn't able to leak out from the acoustic memory foam earcups and have others around you be annoyed.  With this configuration it is possible to have up to 30 dbA of ambient noise blocked once you've put the KNS-8400 on.  Generally speaking, closed back headphones that are sealed like the KNS-8400 usually gives you the impression of the sound coming from within the head and may have a smaller soundstage compared to their open-back counterparts.  A good position that closed-back headphones provide is that they bring you closer to your music, since they are being reflected back into your ears. 

We'll see how KRK decided to put present you reference quality sound meant for mixing and recording.  But we've already heard about their design philosophy being engineered and tuned to offer a sound that is flat as possible so that what you hear represents the true nature of the audio material without coloration or enhancement.

The KNS-8400 is constructed mostly out of hard plastic but it feels solid in all the right areas.  Hidden in the headband area is an adjustable sprung steel skeleton that allows you to adjust the headphone to the size of your head.  Headband pressure is rated at 4 N based on the average sized head.  I don't have a particularly big head, probably about average or smaller than average, so for me the clamping force doesn't feel like a problem for my ears nor my head, the force isn't super tight, but it could be a little tighter.  The fact that I feel there should be more clamping force means they are large headphones.  There is some compromise to be a one size fits all headphone and for me, the KNS-8400 is comfortable for the most part, but there are times when the headband shifts forward or backward if I cock my head back and forth with the music. 

The KNS-8400 comes with a super long straight cord that measures 2.5 meters (or 8.2 ft.) and at times it becomes an annoyance because it flops around and tangles.  It's good for studio use when your source is at a distance, like when you are recording, but becomes a little dangly if the source is close by, it's better to wrap them up in this scenario.  An optional coiled cable can be ordered if you prefer it over the straight cord that is included with the bundle.    The cord is replaceable and detachable.  Connecting to the KNS-8400 is simple and is very secure when in place because there is a lock mechanism in place.  Place it into the socket and turn clockwise to secure the cable, and counter-clockwise to release the cable from the headphone.  The in-line volume control module is basic and attaches to the end of the cable cord and offers a simple min/max setting.

The KNS-8400 offers a 40mm neodymium driver.  The enclosure is covered and there is the KRK logo and model number inside of the circular chrome ring.  I like the styling of the KNS-8400.  A color coded label differentiates left and right drivers.  On top of the headband, another KRK logo is embossed to give it more style. 

Enough talk.  How do they sound?

I've had the KRK Systems KNS-8400 for just about over a full year so I have long-term experience with them.  I'm happy to say that the KNS-8400 has had no issues and everything is still intact with the headphones as they were from the first day. Cushions have not fallen off (unlike some cheap headphones I've used in the past), the cord is still good after all the stress they've been through, and the clamping force is still the same.  These fit over the air, so they have some airiness feel to them.

The KNS-8400 are very comfortable headphones.  The memory foam cushions make it easy your on head and over the ears and while they do get a little greasy at times, they wipe off easily with the provided cloth.  The earcups very much help in reducing sound leakage and providing noise isolation, the KNS-8400 does a very good job at this aspect, but not better than in-ears.  The earcups are quite large and make it easy to fit over the ears.

The KNS-8400 really does offer a very flat and natural frequency response and they are definitely a good choice for mixing.  This is my first KRK product that I've tested so I had to get used to the different sound signature.  The clarity is very bright, clear and vibrant.  The brightness takes a bit of getting used to.  The flatness takes getting used to if you've never heard something naturally flat without any enhancement made to the sound.  Soundstage is surprisingly wide and has great depth.  In general the details were given at a high level. 

Music felt engaging and after a couple of hours, my ears did not get tired.  I noticed a difference when I broke-in the KNS-8400 for a couple of days.  Initially the high's were a bit too harsh, but that went away and what you're left with is something that felt crisp, airy, and a hint of directness.  You can hear the little nuances in the music that you never thought was there.  I find these perform well in music without much bass because the bass is a little lacking.  Mids were great and it provided a sound that was clear and more neutral compared to the highs.  There could be more warmth but I guess this is the KRK signature. 

The only complaint I have with the KNS-8400's is that they lack the bottom end, the bass is a bit weaker than I expected, and it shows after you've mixed and heard a something different with the bottom end when played back on your stereo and in the car.  There's not enough of it and you may think you need more bass when laying down some tracks but in actuality you need a bit less because once you play it back on a different system, you find out the bass is a little more than you expected.   I wish there was a bass boost type of setting with the in-line volume control.  That would have been a welcome addition and possible solution.  But with that said, the bass is tight and punchy when you're able to hear it on specific bass heavy songs.  I guess this aspect always comes down to personal preference. Though for mixing, flatness across low, mid, and high are what you are aiming for.  These are not going to be the headphones you slip on if you're watching a movie or playing games, you'd want something that has more character and enhancement.

The KNS-8400 is harder to drive than some other headphones/in-ears because of their higher impedance of 36-ohms.  While they don't really need to be driven with an amplifier, I would recommend it because on some of my devices, the volume isn't loud enough without an amp, but it depends on what you're using.  If using a Smartphone or mobile device, it'll likely be tough to drive these headphones because of the higher impedance. The general rule of thumb is the lower the number of ohms, the easier they are able to be driven, meaning the easier noise is able to travel (louder audio).

Where To Buy

The KRK KNS-8400 has an list price of $199.99USD.  For the time being it is now on sale at for only $145.70 (27% off) with free shipping!  The product is fulfilled by Amazon so you can buy with confidence.  I love Amazon and their service.

If you are thinking of purchasing the KRK KNS-8400 Closed Back Studio Monitor Headphones, please use our Amazon link, it will help us out greatly.


The KRK Systems KNS-8400 represents an attractive value proposition for those who want to hear accurate sound because of the price point.  For around $150 I think the KNS-8400 is very well worth the consideration and I think you would be hard pressed to find a better product for the price. 

The performance coming from the KNS-8400 is something to be heard and is a top contender because of the details across the range. From mid to high, the detail is very good, and even though I feel that the low end is lacking, I think it helps reveal the clarity of the mids and highs.  The KNS-8400 are comfortable for longer periods of time, though you might have to readjust the headband every so often.  The KNS-8400 misses out on our Editor's Choice Award, but it's not too far off. I can easily recommend the KRK Systems KNS-8400.



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