The CKS99s are, without a doubt, a consumer-oriented headphone in its sound signature. However, despite the prominently advertised bass and the definite emphasis toward that end, the very well-controlled lows rarely step out of place.
 
First off the design and build.  Like other members of the CKS lineup, the CKS99s are a half in-ear design. The shells are larger and stick out a bit when wearing them. They are made of metal, but also high quality soft plastics where it comes in contact with your outer ear.  The cable is thick and slightly rubbery and generally very nice and terminates to a compact L-plug. Overall I think it is quite well built.
 
I found the design to be quite comfortable. Like other half-ear designs, the shell nests in your outer ear.  They were quite comfortable for me, though people with smaller ears may have some difficulty.
 
Given the half-in-ear design, the isolation is quite good.  It comes with four pairs of silicon tips, and I use the second largest. They isolate almost, but not quite as well as my more traditionally designed earphones, such as the Hifiman RE-400s. That said, I've never been a fan of double flanges, so I am generally satisfied with a decent single-flange seal.  Those who prefer deeper seals may have problems getting them due to the design. Cable noise is also not too prominent, given the half-ear design.
 
The package also comes with a nice leatherette case.  Of all my earphones, this is my favorite case because it uses a very convenient magnetic button rather than a zipper.
 
I've owned these for about six months now, so they are well burned in from use. The CKS99s advertise its solid-bass feature and delivers on that front.  However, I would emphasize that the bass is very high quality and the "solid" description is quite accurate.  I don't consider the bass to be very boomy or splashy, but rather very well controlled.  In fact, there does not appear to be a lot of sub-bass emphasis. Instead, there seems to be a bit of an upper-bass hump, which makes the music sound more substantial (or thicker for those who don't like that sound).  I use these for a variety of genres, from indie-pop and indie-rock to mainstream pop and hip-hop, along with some more acoustically inclined songs and instrumentals. They are definitely great for hip-hop and mainstream pop, but even for my other genres, I don't feel like the bass gets in the way.
 
The rest of the sound is quite good as well.  The mids are slightly recessed, but does not sound veiled and is still quite detailed.  The presence of the upper-bass helps to prevent it from sounding hollow. The highs are a bit more prominent than the mids, and surprisingly detailed with good separation. Even when I'm listening to music with little or no bass, the level of detail and instrument separation is quite impressive. The details and crispness is retained even though I would not categorize these phones as bright. I am somewhat sensitive to brightness and fatigue, so I appreciate that I can wear these for hours, though admittedly, I recall them being a tad bright before burn-in.
 
Overall, these are probably my favorite earphones in my possession.  They have a definite consumer-oriented v-shaped sound with bass (the low end is more emphasized than the high end), so they're not going to be analytical, but they're definitely fun and have some very good qualities than just good bass. For the price, I think they're a good value, though this price range has many good options.
 
Quick comparison to other IEMs in my possession.
 
Hifiman RE-400s: The RE-400s are a completely different type of IEM, though the price range is somewhat similar. The Hifimans are very neutral and analytical compared to many IEMs in the price range. While I praised the CKS99s for their detail and separation, I think the Hifimans are even better in this regard.  The Hifimans are also quite fast and nimble, though the CKS99s are not slow by any stretch of the imagination. The bass in the CKS99s are obviously more prominent.
 
AKG K374: Also in a similar price range.  Like the CKS99s, the AKGs are consumer oriented with a bass emphasis. In terms of bass quantity the AKGs and the CKS99s are close, but the CKS99s are much better controlled.  The AKGs are less mid-recessed so in that sense it's flatter and they sound less dark, but they are definitely not neutral by any stretch of the imagination.  The AKGs also trail the CKS99s a bit in terms of detail and separation, but the AKGs are not bad at all in this regard.
 
Klipsch S4: The Klipsch are mainstream favorites, but I would recommend either the AKGs or the CKS99s to a mainstream user before the Klipschs.  The Klipsch can be appear quite detailed, but it's more of a function of brightness. They are also quite fatiguing. The highs and mids on the S4s are harsh compared to the CKS99s.  The bass is also much looser in the S4s than the CKS99s.

Introduction

First off, I’d like to thank the folks at Audio-Technica for providing a review sample of the CKS99. Up for review is the mid-range entry into the Solid Bass line of in ear monitors from Audio-Technica, the CKS99. So, without further ado, let’s get right to it, shall we?
 
Accessories: The CKS99 comes with four pairs of silicone eartips, a set of manuals and a leather carrying case.
 
Design and Build Quality: The housings of the CKS99 are plastic and similar to the CKS77 but feature a few nicer accents to differentiate it from the lower end model. Overall, the earphones seem nicely built with sturdy cables and black plastic housings with a soft touch feel to them around the edges where the housings come into contact with your outer ear.
 
Comfort: Like the CKS77, the fit of the CKS99 could be a point of contention for some but I was once again very pleased with the fit of the CKS99 as it was quite comfortable for me over long periods. The driver sat in my outer ear nicely without exerting any unpleasant pressure.
 
Isolation: These isolate very well for a vented dynamic IEM.
 
Microphonics: A tad unpleasant at times but nothing excessive.
 

Sound Quality

Burn in: The CKS99 was given 50+ hours of burn in time prior to review and no significant changes were detected.
 
Like the CKS77, the CKS99 features prominent bass, a clear but recessed midrange and prominent treble. To go into further detail on the sound signature and the ways in which it improves over its sibling, let’s start at the bottom.
 
The bass is big and full with slightly more emphasis on the midbass than sub bass and merely okay extension. If there’s a lot of midbass emphasis on a track, the midbass hump will become incredibly obvious and distracting. Mid bass has a tendency to step up on the lower midrange which can end up sounding rather “thick” as a result.
 
The midrange retains some of the “hollow” character from the CKS77 but is surprisingly forward in presentation. Instruments sometimes sound a bit recessed but vocals are front and center. The midrange as a whole is actually rather smooth and detailed. Claritiy is good and the presentation is reasonably linear. In terms of pure detail, the CKS99 is ahead of its sibling but not quite on the level of the RE-400.
 
Treble is a bit less even and the lower treble is occasionally prone to sibilance but on the whole, the airiness of the treble combined with its good presence and great extension make it rather pleasant on the whole.
 
Presentation wise, the CKS99 eschews a bit of the claustrophobic spaciousness that I noticed on the CKS77 and sounds just as open but even more intimate, with vocals being very forward in the presentation. This sounds rather odd, considering the slightly recessed nature of the midrange but there it is. Along with the big bass, vocals do a great job of standing out and being heard.
 

Conclusion

Now this is where things get interesting. The CKS99 retails for $150 while the CKS77 retails for $120. On Amazon, however, I’ve found the CKS99 for $93 and the CKS77 for $99. If you’re in the market for either one, the CKS99 is easily the better pick.
 
Like the CKS77, however, the CKS99 also comes with some qualifiers. If you’re looking for big bass and have the large-ish outer ear canals to fit them, the CKS99 is a pretty good choice for the price, even the higher than $99 retail price. . If you’re looking for a more rounded experience, that’s what the RE-400 is for. The strength of the low end and the strong midbass emphasis may be a turn off for some audiophiles but the sound signature is more or less in line with Audio-Technica’s “house sound” and is warm and pleasant across a number of genres and I found them surprisingly enjoyable for Jazz. On the whole, if you’re looking for an earphone with big bass between $100 and $150, the CKS99 is a very solid choice.
 
Re-Posted from my site, Musical Musings