I bought this Cks990 through Aliexpress for 32USD.Official Amazon price at USD130++. Has been using it extensively for last 3 weeks with total burn in period of over 100 hours. Are they original Audio-technica product. I don't know. I does look and feel like an expensive earphone. Does it sound good? no. Because it sounds excellent 
. I only have one brand new in box {BNIB} Audio-technica product which is the IM50. I bought it at full price of USD60, just for comparison purpose when I bought earphone from AliExpress. So far it has done it job excellently as my benchmark for 60USD earphone.
Cks990 with my current source, Samsung Galaxy S Advance {2012) and Topping NX2 DAC/amplifier. S Advance is currently the best sounding and loudest smartphone that I currently have. Unfortunately it is and ancient smartphone which tend to freeeze after extended music play. Better than my latest smartphone Ulefone Power and previous smartphone HTC Desire 820s and Nokia Lumia 620. The only smartphone that is superior than all smartphones mentioned here was the late Lenovo s930. Yes late=dead. The L shaped earphone jack is pretty in red with proper strain reliver. Cable is dual channel design just like my Audio-technica IM50. It is tough and has moderate resistant to tangle. It has almost no memory effect and can be straightened almost immediately after coiled inside round semi hard case. The unsual fact about this design? While listening to Amber Rubarth binaural album, somehow the left-right sound has reversed. In the recording one side {left if not mistaken} has female voice and on right has male only. But all my other earphone has totally reverse sound (right-female, left-male). Not that it affect the overall sound quality. Just it feels weird.
One of the most good looking earphone that I ever have. With original black core tip which is both comfortable and secure in ear. As usual it follow CKS line design with 2 chambers. One for the 13mm Dual Magnetic Field Driver - for whatever it is. And another one as a reverberation chamber. I suppose it act to widen the soundstage and the airiness of sound( hope I give correct definition here).
Make no mistake, cks990 is a huge earphone by any standard. It may looks like normal size but I have fairly big ear. That is why I am using the largest size ear tip that come with the earphone. The design is semi in ear, so only the nozzle and silicone tip will be inside ear canal. The reverberation chamber is protruding out significantly and obviously it cannot be used while sleeping on the side. Thankfully for clever design and lightweight material used the housing sit really comfortable and secure in ear. Also with the help of long black silicone cable strain reliever. And with usage of big and grippy silicone tip it really help blocking allmost all environmental sound even at low volume.
Sound;
Initial sound out of box{or package in this case } - extremely big and boomy bass with some treble heard. Really big soundstage and airiness of sound.Thanks to the dedicated reverberation chamber. Bigger than CKX9, FXT90 and EX650. Vocal is clear and some details heard. So it sound almost like L shaped. So I just use it for normal music play at medium volume and slowly can detect some noticeable improvement in overall sound. The big/boomy bass has become slightly lower but tighter, faster and more impactful. Even though cks990 is a true Solid Bass earphone, somehow the bass never reached what I believe basshead level. If I have to quantify the bass I will rate the amount at 8/10. Other basshead level earphone like Pioneer se-cl541 and Denon AH-C100 has 9/10 bass amount{according to my own ear}. This is actually a plus quality since the bass didn't overpower the treble and vocal. It mixed nicely with treble {rate at 7/10 in amount} and thus produce a heightened kind of balanced sound. At current burn in period of 100 hours, the treble amount has rise significantly to an acceptable level. It sound almost metallic like {ala Audio-technica ckb50 treble} without any noticeable sibilance. It is definitely not considered as sparking or bright, but for a Solid Bass line it is already considered excellent.
As a Solid Bass earphone Cks990 has unusual amount of details. Not as details as Sony EX650 or LZ-Z03A but very close. The vocals are very clear and I can hear new background backing vocal that I never heard before, especially with sub 20USD earphone like Boarseman CX98, Rock Zircon and UiiSii HM7. So in summary Cks990 has a heightened kind of balanced between bass-treble together with fantastic details and clear vocal. Cks990 has really big soundstage and airiness of sound uncontestable by any of my other current earphones.
Comparison with CKS55;
Never own this Cks55 but it is widely available in most Audio-technica demo rack. No contest here. Cks55 has a definite L shaped sound. The bass is boomy and not as impactful. The vocal and treble is obscured by the overwhelming bass. Still good but if you have choice and money Cks990 is the way to go.
Comparison with Pioneer se-cl541 ;
Was the king of bass before Cks990. The amout of bass is insane, tight and thumping. Overall better than Cks55 with slightly clearer vocal and moderate amount of treble. Extremely good with EDM/metal just like Cks990. I never use it lately because of imbalance channel{ right side sound slower}.
Comparison with Audio-technica IM50 ;
The reference for the Aliexpress buy. This earphone sounds excellent on its own. But the value come with its excellent construction and cable. When I compare it to cks990 initially IM50 sounds better. After 100 hours burn in, cks990 has managed to outperform IM50 in overal sound quality. The bass amount for IM50 rated at 6/10 and treble at 7/10. The bass is not as impactful and fast as cks990. But treble is better with IM50. Otherwise soundstage, vocals and details all leaned towards cks990. Generally IM50 is one of the most balanced sound earphone in my collection. CKS990 sounds better because of its better mixture of bass-treble along with wider soundstage. Build quality is on par for both. Cks990 is more comfortable and secure even with below ear hearing style vs over ear of IM50.
Conclusion ;
Cks990 has rise to no 4 spot in my own collection ranking/preference. The top 3 are FXT90, EX650 and CKX9. Why I am preferring those 3? Easy because I am more a treble-head than bass head. Most of my music collection are metal, rock with some EDM and pop. They are handled admirably by those 3. In occasion when I decide to listen mostly to metal/EDM Cks990. I will definitely not recommend this Cks990 to everyone, especially with small ear since it can be overwhelmingly big and probably heavy in your ear. Secondly because it is not suitable for all kind of music. If you only want to have just one earphone to listen to every musc genre this is not your answer. Choose it for correct music it will reward you with excellent, engaging and fun sound.
. I only have one brand new in box {BNIB} Audio-technica product which is the IM50. I bought it at full price of USD60, just for comparison purpose when I bought earphone from AliExpress. So far it has done it job excellently as my benchmark for 60USD earphone. 
Cks990 with my current source, Samsung Galaxy S Advance {2012) and Topping NX2 DAC/amplifier. S Advance is currently the best sounding and loudest smartphone that I currently have. Unfortunately it is and ancient smartphone which tend to freeeze after extended music play. Better than my latest smartphone Ulefone Power and previous smartphone HTC Desire 820s and Nokia Lumia 620. The only smartphone that is superior than all smartphones mentioned here was the late Lenovo s930. Yes late=dead. The L shaped earphone jack is pretty in red with proper strain reliver. Cable is dual channel design just like my Audio-technica IM50. It is tough and has moderate resistant to tangle. It has almost no memory effect and can be straightened almost immediately after coiled inside round semi hard case. The unsual fact about this design? While listening to Amber Rubarth binaural album, somehow the left-right sound has reversed. In the recording one side {left if not mistaken} has female voice and on right has male only. But all my other earphone has totally reverse sound (right-female, left-male). Not that it affect the overall sound quality. Just it feels weird.
One of the most good looking earphone that I ever have. With original black core tip which is both comfortable and secure in ear. As usual it follow CKS line design with 2 chambers. One for the 13mm Dual Magnetic Field Driver - for whatever it is. And another one as a reverberation chamber. I suppose it act to widen the soundstage and the airiness of sound( hope I give correct definition here).
Make no mistake, cks990 is a huge earphone by any standard. It may looks like normal size but I have fairly big ear. That is why I am using the largest size ear tip that come with the earphone. The design is semi in ear, so only the nozzle and silicone tip will be inside ear canal. The reverberation chamber is protruding out significantly and obviously it cannot be used while sleeping on the side. Thankfully for clever design and lightweight material used the housing sit really comfortable and secure in ear. Also with the help of long black silicone cable strain reliever. And with usage of big and grippy silicone tip it really help blocking allmost all environmental sound even at low volume.
Sound;
Initial sound out of box{or package in this case } - extremely big and boomy bass with some treble heard. Really big soundstage and airiness of sound.Thanks to the dedicated reverberation chamber. Bigger than CKX9, FXT90 and EX650. Vocal is clear and some details heard. So it sound almost like L shaped. So I just use it for normal music play at medium volume and slowly can detect some noticeable improvement in overall sound. The big/boomy bass has become slightly lower but tighter, faster and more impactful. Even though cks990 is a true Solid Bass earphone, somehow the bass never reached what I believe basshead level. If I have to quantify the bass I will rate the amount at 8/10. Other basshead level earphone like Pioneer se-cl541 and Denon AH-C100 has 9/10 bass amount{according to my own ear}. This is actually a plus quality since the bass didn't overpower the treble and vocal. It mixed nicely with treble {rate at 7/10 in amount} and thus produce a heightened kind of balanced sound. At current burn in period of 100 hours, the treble amount has rise significantly to an acceptable level. It sound almost metallic like {ala Audio-technica ckb50 treble} without any noticeable sibilance. It is definitely not considered as sparking or bright, but for a Solid Bass line it is already considered excellent.
As a Solid Bass earphone Cks990 has unusual amount of details. Not as details as Sony EX650 or LZ-Z03A but very close. The vocals are very clear and I can hear new background backing vocal that I never heard before, especially with sub 20USD earphone like Boarseman CX98, Rock Zircon and UiiSii HM7. So in summary Cks990 has a heightened kind of balanced between bass-treble together with fantastic details and clear vocal. Cks990 has really big soundstage and airiness of sound uncontestable by any of my other current earphones.
Comparison with CKS55;
Never own this Cks55 but it is widely available in most Audio-technica demo rack. No contest here. Cks55 has a definite L shaped sound. The bass is boomy and not as impactful. The vocal and treble is obscured by the overwhelming bass. Still good but if you have choice and money Cks990 is the way to go.
Comparison with Pioneer se-cl541 ;
Was the king of bass before Cks990. The amout of bass is insane, tight and thumping. Overall better than Cks55 with slightly clearer vocal and moderate amount of treble. Extremely good with EDM/metal just like Cks990. I never use it lately because of imbalance channel{ right side sound slower}.
Comparison with Audio-technica IM50 ;
The reference for the Aliexpress buy. This earphone sounds excellent on its own. But the value come with its excellent construction and cable. When I compare it to cks990 initially IM50 sounds better. After 100 hours burn in, cks990 has managed to outperform IM50 in overal sound quality. The bass amount for IM50 rated at 6/10 and treble at 7/10. The bass is not as impactful and fast as cks990. But treble is better with IM50. Otherwise soundstage, vocals and details all leaned towards cks990. Generally IM50 is one of the most balanced sound earphone in my collection. CKS990 sounds better because of its better mixture of bass-treble along with wider soundstage. Build quality is on par for both. Cks990 is more comfortable and secure even with below ear hearing style vs over ear of IM50.
Conclusion ;
Cks990 has rise to no 4 spot in my own collection ranking/preference. The top 3 are FXT90, EX650 and CKX9. Why I am preferring those 3? Easy because I am more a treble-head than bass head. Most of my music collection are metal, rock with some EDM and pop. They are handled admirably by those 3. In occasion when I decide to listen mostly to metal/EDM Cks990. I will definitely not recommend this Cks990 to everyone, especially with small ear since it can be overwhelmingly big and probably heavy in your ear. Secondly because it is not suitable for all kind of music. If you only want to have just one earphone to listen to every musc genre this is not your answer. Choose it for correct music it will reward you with excellent, engaging and fun sound.
