Sony's flagship again

I have used quite a number of Sony earphones, namely E837, E838, E888, E931and EX90. While EX90 is the most expensive one (HKD$668), I think it is worth the money.

Sound
Crisp and clear with great transient response, plucking and percussive instruments sound extremely clear. Bass are tight, clear and deep but not excessive, for example, bass in male voice does not interfere with instruments with lower bass such as contrabass, bass drum and various kinds of synthetic basses. I tried Shure E2c before, they have plenty of bass but are dull and blur, EX90 never have this problem. Apart from bass, the mids and treble also share the same character -- crisp and clear. To talk about break-in, EX90's initial sound is not terrible (if you have tried E888 you know what I mean) but the mids will become slightly louder as you use it, maybe it is placebo ;-) However because of the outstanding transient performance, some undesirable sounds such as excessive amount of vocal sibilants may also be heard in songs.

Comfort
The only in-ear earphones I used are E2c and EX90 so I can only compare these two. E2c provides three pairs of foam buds and three pairs of rubber buds but all of them are uncomfortable. The rubber buds are too hard and unable to seal well, the foam buds expand in my ear canals and make me feel pain. EX90's earbuds are, on the other hand, very soft and seem fragile. They are much comfortable than E2c. However, because you still need to insert the earbuds into your ear canals, so do not expect they will more comfortable than traditional earphones.

Isolation
Do not expect good isolation from the EX90. It is only slightly better than traditional earphones.