Audio Technica ATH-CKM300:
I call this CKM500's little sister. Everything from the build quality, design, comfort, sound isolation and microphone is identical to it. So I'll just focus on sound quality because that is where the two have differences.
 
Sound Quality:
The sound that this earphone delivers is in no way neutral. The sound is more emphasized at midrange and treble, while the upper bass takes everything behind. This kind of delivery brings so much detail and clarity in sound. I'll break down the SQ in each category: bass, midrange, treble and soundstage.
 
Bass:
Bass is very defined. Upper bass and mid bass is tight and controlled. Since the bass here is tight, the lower bass wouldn't create a "boomy" or airy sound. Bass is presented at the back.
 
Midrange:
Midrange is perfectly refined. It delivers the mid with so much clarity. There is absolutely no veil in the mid. It's the classic Audio Technica midrange. Midrange is presented at the front.
 
Treble:
Treble is very detailed and clean with no sibilance. The way it is delivered brings so much excitement in sound. Treble is presented at the sides.
 
Soundstage:
Because of so much details in sound that it delivers, it will sound a bit intimate.

Build:
Build quality is decent. But the J-cord flat cable is a nightmare. It's so bad that I would consider it as a deal-breaker. First of all, I have no problem with J-cords. But for a J-cord with stiff flat cable? It's possibly the worst combination ever. Not to mention that they've placed the remote just beneath the left earpiece. That means the remote will always stick out right beneath your left ear and produce a lot of cable noises. And it's such a hassle to use the remote because of the placement. I would much prefer if it was placed lower. And the cable splitter is a garbage. It was designed in a way that it the left cable won't stick out if you are NOT wearing the the left earphone. But once you wear the left earphone, the cable would just stick out right in front. I find all of these very annoying.
 
Comfort:
For my ears, the flimsy silicone eartips from Sony is very uncomfortable. That type of eartips would just suck my eardrums and me headache. So I've just changed the eartips. Plain simple. What I find very uncomfortable is the cable noise produced by the J-cord. The huge remote and the flat cable would always rub against my neck. I found an easy solution for the right cable by using the clip provided in the package. But the left cable that has the remote is the biggest issue here. And up to now, I found no solution to it.
 
Sound Quality:
 
-Bass: Very exciting. Mid and lower bass is amazing in this earphone. It has some kind of slam to it that makes it sound very rich and thick. However, the upper bass is pretty loose. It lacks tightness which results to a bit muddy sound.
 
-Midrange: Very smooth. Though it will tend to sound a bit hazy whenever the bass hits hard.
 
-Treble: As smooth as the mids. Though this time, it is very underwhelming for me to be honest. The treble in this earphone presents too less details. It makes songs sound very dry and lifeless. Kills all the excitement produced by the bass.
 
-Soundstage: Spacious. But because of the lack of treble, the bass is just everywhere which make it sound a bit unclean and plasticky.