It is worth repeating that the MH755s etc you see online are most likely copies. I have reason to believe that my IER-H500A and EX255AP are copies as well. The fact is that I bought Sony fakes: EX255AP and H500A both have a somewhat uncertain weak cable (difficult to distinguish from the real version), both have earpieces without the dots to signify size differences, and both the pouch and the cable adjuster have Sony logos that seem to be a different typeface. Other than these differences, the sound may also be different, but for the unacquainted listener, they are quite 'good quality fakes'. It would be very costly to copy it all, and scrimp on sound quality – they sound superb by the way! To make a forgery at this level would not have been easy. It is easily a very good thing they have done because they have replicated the original to a high degree but only charge a fraction of the original cost (but it is difficult to say that its cost performance is good as this is a deception). The shiny Sony authenticity sticker is also missing. Sony fakes have been around since EX90SL second hands floating around in Japan. Subsequently I also looked into a TRN MT1 with 2 for just $14 AUD. It’s just a 10 mm DD and nothing fancy but people are happy with it which is what matters.
IEM comparisons are very easy and highly subjective. The differences are large and preferences divide in a similar way for most people - those who value details and dislike EX255, and those who like bass or just need to hear voice and so are fine with EX255.
Result: EPH52 is best, EX150 and H500A also quite detailed.
EX255 is deeper, so one needs to turn down the volume, and details are simply overborne by low frequencies! It emphasises deep sounds a bit too much and not in a pleasant way either. I simply cannot stand EX255 after using EPH52, EX150 and H500A.
Fake H500A is similar to EX150 in terms of hearing details but seems to not be as good as EPH52 … but acceptable for the price.
TCM125 is more 'squeaky' for strings (no air, not open), a somewhat different (unrealistic) piano tone. Only the barest audience sound, so not detailed. Possible to EQ however.
Earbuds like MH410c have a duller, boomy sound that blurs the sound of piano. It was the opposite effect for string instruments where IEMs sounded squeaky and untrue but earbuds were perfect. No inkling of audience or details at all! E706, CASIO EX Word earbuds slightly less boomy but still same kind of sound. No audience sounds. My random $3 IEM is a flawed design, sound comes from far away, dull, sounds like a musical box, dreamy sound. Hurts ears if turned higher. Seems very easy to drive. Alcatel earbuds sound like a bad EQ. missing frequencies or sth. Like sound emanating from poor speakers in a box with you inside it and yes, dull, boomy sound with added unnatural EQ. EPH52’s strings are probably truer to the source than the earbuds. Piano definitely sounds better on 3 IEMs.
Earphones are great because headphones make my neck tired. When I first listened to EX255, I thought, "It sounds like a phase shift when I apply extreme EQ". The impression of the sound is a sense of pressure in the low frequency range. The mid-range is cut down and there is less of a component around the base note, so the rawness of the instruments is lost to some extent. I mentioned that there are few components around the base note, but if there are too many base notes for the overtones, the sound will be sharp and painful to the ear. The fit is very good. I think these earphones produce too much bass, depending on the recording conditions. Bass is a kind of vibration or wind pressure that you feel with your whole body, not with your ears. The earphones are designed to reproduce the sound you hear in your ears, so it's hard to ask for more than that. Piano sounds unbalanced. The call function is excellent. You can hear the person you're talking to very clearly and close, and there's no noise, so it's easy to talk to them. However, for music it is a pain for me personally, so I can't stand using it. The only thing that is confusing about this review is the lack of specifics as to what kind of music you are listening to and how you rate it accordingly. I usually listen only to classical music, so I want to have a range of sound. The sound balance of this product is very unbalanced compared to the EX150 that I have used so far. The balance of sound is very unbalanced. I have to turn up the volume to hear details. Of course, if I did that, my ears would break and I would have to remove the earphones. As for the bass, it is adequate, so there is no problem to listen to a low frequency solo, for example, a solo piece of cello, or a piece of piano without much high frequency. However, it is not suitable for classical music, especially symphonies, as the sound is delivered in a balance of bass, midrange and treble. My friend uses the XB55, which is a bass-oriented model of the same series, so I borrowed the XB55 and listened to classical music and found it difficult to find a balance between the bass and the treble. In conclusion, I think the EX150 is better balanced for me personally. EX255AP doesn’t sound natural. It’s got a distinct flavour and this could be because it’s a fake. EX255 clearly sounds like craggy squeaking ragged paper for strings compared to earbuds which sound open and natural, while the fake sony is narrow and squeaking. The Real EX150AP is pretty much the same so it’s not a forgery issue. EPH52 also … like a different atmosphere but still narrow and squeaking compared to earbuds. Conclusion is that if you don’t care or compare you won’t notice that what you are hearing is very low-fi! At some point one can no longer distinguish between preferred sound and bad quality sound.
As a side note, ZX110 does have an older sibling ZX300 series just like EX150 has the EX250 series, and for some reason the more expensive sibling has a tendency to perform badly in listener’s subjective tests. The subjective tests are so unreliable though. It is always done differently, on a whim. Today the sound might be bright, the next, dull; if you only listen to a bad loudspeaker it can be difficult to remember what a good performing speaker sounded like, or should sound like. But if multiple subjective tests point to the same overbearing bass then it probably is the case.