Knowledge Zenith, otherwise known as KZ, is as the title says � an enigma. That�s because we don�t really have that much information about them, and also because they�ve never bothered to release any of that. All we know is that they�re a Chinese manufacturer that makes a crap ton of ultra-cheap IEMs that they sell through online marketplaces like Aliexpress. That, and they have a massive cult following on Head-Fi that practically worship the brand with every post they make on the Asian brand thread or their official appreciation thread.

But I�m gonna get straight to the point. I don�t like KZ. I�m not gonna lie about that. I don�t like their lack of presence as a company. I don�t like their lack of ways to contact them. But I couldn�t ignore the cultish hype. It had me curious as to if they really were worth the continuously-spreading hype. And just a few weeks ago, the opportunity presented itself. And so here I am, reviewing one of the many IEMs from the brand I love to hate. Will they stand up to my expectations? Find out after the jump.

The ED9 comes in a plastic shield-shaped case devoid of marketing buzzwords and text, save for a list of specifications on the back of the case. It�s no Pistons 3.0, but at least it isn�t a shameless cardboard box. Inside is the ED9 itself, along with its surprising accessories package of three extra eartips and � get this � a pair of extra tuning filters.

Yes, tuning filters. I know, I couldn�t believe it myself. You really don�t get to see tuning filters � a feature more commonly found in IEMs priced $100 or above � in an IEM priced below 20 dollars. There is nothing on the package that explains what either of them is, but from here on out I�ll just call them the bass filter and the balanced filter. Build-wise, they don�t disappoint either, with rather weighty full metal housings and a surprisingly robust cable. The strain reliefs are built pretty well, and its right-angled connector is pretty solid, although I feel the diminutive Y-split might become a point of failure for the IEMs in the future. As much as I hate to admit it, I�ll say I�m impressed at how much KZ is able to pack into this sub-$20 package.

But no audio gear is without its faults, and the ED9 does have its fair share of failures, mostly in the build. Once you go past the first glances, full metal housings don�t really matter anymore when the drivers themselves have a channel imbalance issue straight out of the box. The robust cable doesn�t seem as much of a good thing anymore when it�s practically a partially-uncoiled spring that�s almost impossible to completely straighten out. And worse yet, the audio started to cut out the very first time I plugged it in. (I�m not exaggerating anything � that really did happen the first time I took it out.) But let�s face it � KZ is your typical Chinese manufacturer of cheap products. Knowing this, there�s really no surprise that they have little (if any) quality standards when it comes to mass-producing their products. But if it�s this praised throughout the budget Head-Fi community, this is an issue that becomes all the more important.

The ED9 actually doesn�t fit too badly, staying snug and secure in my ears whether you wear it straight down or loop the cable around the ear (that is, if you can � the cable is incredibly stubborn and literally jumps out of my ears when I try to loop it around the back). However, the ED9 seems to have a sealing or damping issue, as the IEMs do not isolate equally (one side isolates less than the other). I don�t know how exactly this happened, but it has already been like this straight out of the box, so there�s not much else to blame other than poor quality control on KZ�s part. Again.

The source equipment used in this review is a fifth-generation iPod Touch and an iPad 3 directly running the KZ ED9, and a PC running iTunes 12 and Foobar2k powering the Jive through a Schiit Fulla DAC/Amp. The EQ apps used in their respective test is TuneShell on iOS and Electri-Q on the PC. The eartips used on the S3 are the included medium size eartips. The list of the test tracks I listen to while reviewing the Jive can be found here, although I will include links to specific songs in the review for a more direct point of reference.

The ED9 was burned-in for around 50 hours prior to writing this review. I noted no changes over this period, so I doubt there would be any more over time. In any case, let�s talk about how they sound.

Bass Filter:

The ED9�s sound is honestly really hard for me to assess as the channel imbalance is practically splitting the IEM into two different sound signatures, each channel having its own twist on the sound. And I�ll be honest, I literally have no idea which is supposedly the �correct� sound of the ED9. The right channel is just a bass monster, with massive bass whatever you listen to. Its extension and sub-bass presence is phenomenal, easily taking the �Most Sub-Bass in an IEM Award� in my entire collection. It�s so massive that it tends to overwhelm the rest of the signature with all its slightly-distorted glory (Daft Punk � Motherboard). It�s so massive that I can practically feel the bass in Condukta�s Virtual Oasis. But the strange thing is, they manage to fall back and make way for the midrange when the song doesn�t explicitly have a heavy low-end (Yiruma � Fairy Tale). Its soundstage is also pretty good, with an airy space that reminds me of the Pistons 3.0.

The left channel, however, has a much more subdued low-end, sounding quite like the Pistons 3.0. The bass doesn�t overwhelm at all, instead sounding very controlled and refined. Again, I really have no idea which is supposed to be the �correct� sound here, but as the right channel seems to actually seal properly, I�m pretty sure the bass monster should be how the bass filter sounds.

Balanced Filter:

A visual comparison of the filters. Bass filter on the left, balanced filter on the right.

The balanced filters, in my opinion, really bring out the �true� sound of the ED9. The reason why I call it its �true� sound is because the balanced filters, well, don�t have any actual filters � it�s little more than a brass tube to hold the eartips. (In contrast, the bass filters have a black mesh that dampens a treble spike as seen in the image to the right.) The ED9 sans damping filter is more bass-light, bringing out more clarity and focus to the midrange and treble. The bass is still there, but it�s taken a few steps back, really bringing out the rest of the music to life. Guitars sound great (Sungha Jung � Coming Home). Pianos sound great (Yiruma � Indigo). Pretty much everything sounds great (Daft Punk � Give Life Back to Music). Can�t really say much more than that.

Summary:

Substandard quality control aside, I�ll admit, the ED9 sounds pretty great (how many times have I said that already?). It doesn�t have the straight-up versatility of, say, the Pistons 3.0, but its two pairs of filters do an equally effective job providing two different flavours of a similarly refined sound. So yeah, I�m gonna say it � the ED9 sounds pretty darn good.

Okay, now I have a really hard time gauging how well the ED9 does here. Simply put, the channel imbalance really messes up the soundstage enough that I simply can�t use this for gaming properly. Audio cues coming from the left are rather distant and hard to pick out. Movies have the same problem. So no, I cannot give a proper rating of the ED9 in this section in its current condition.

The KZ ED9 was designed from the outset to work with phones and similarly weak sources, so one will have no trouble using it with your phones or iPods or whatever audio device you might have. Pairing it with the Fulla, I didn�t really notice any major differences sound-wise, beyond them sounding cleaner out of the Fulla�s improved DAC chip. Now, about EQ�ing the ED9�I really don�t see any reason why one would bother to tweak the sound through software when you�ve got an excellent hardware �EQ� from the get-go. So I guess I�ll leave it at that � there really isn�t much more to say at this point.

The KZ ED9 can be bought from the official KZ store in Aliexpress, or a bunch of other sellers such as Gearbest for under $20. I would say the KZ ED9 offers incredible value at its price point, with its great build, great package, and innovative tuning filter system that really pinches the profit margins. But as much as I�d like to gush about its merits, all of it is shrouded by the fact that it came in partially broken. Is it really worth getting? To be honest, I can�t really bring myself to say yes, despite all the positives.

Versus MEE Audio M9 Classic ($10):

The MEE Audio (formerly MEElectronics) M9 Classic was an impressive budget IEM, offering an unprecedented level of quality across the board at the rock-bottom price of ten dollars. From a sound standpoint, the ED9 easily blows the M9 out of the water with its refinement, its more balanced sound, and its neat tuning filter features. But when you consider the rest � the rest being the ED9�s iffy QC � the M9 ends up standing out as the winner in this face-off.

Versus Pistons 3.0 ($16):

I don�t think there�s anything to say here that I haven�t already said throughout the review. In the end, pretty much everything else beats out the ED9 by the fact that it�s not half broken. If, however, you manage to not get a dud pair, the ED9 will give you a brighter, more forward, and more aggressive sound compared to the passive-sounding Pistons 3.0.

Earlier in this review I called KZ an enigma. But having studied and reviewed their ED9 I can say I have KZ all figured out. KZ is a manufacturer that designs very promising earphones that look to be worth it for the price, but their apparently horrible quality control leaves me still wondering why they have such a massive cult following � a cult following that bothers to spend over $100 dollars on 10 pairs of IEMs instead of two or three actually well-made pairs. They seem to not care about anything beyond designing the IEMs and stuffing them with neat features and an otherwise excellent sound. Beyond that, no, I don�t think they seem to care about actually making their products properly and consistently.

Whatever the case, as much as I want to like the ED9, I cannot recommend them under these circumstances. I know my complaints will fall on deaf � or rather, non-existent and foreign � ears, but KZ, straighten up your production process.

FIX THE QUALITY CONTROL. I don�t think I�ve pressed a point any harder than that.

I would like to again thank George at Gearbest.com for providing the sample of the KZ ED9 you see in this review. You could check out the rest of the images I took during the shoot here (link unavailable), and you could check out some more of my reviews here.

This has been thatBeatsguy of DB Headphones; thanks for reading!