From vrnl comparation- EarSonics SM64: the ES IEM has less forward mids and a more V-shape sound than the FA4. The FA4 is always slightly V-shaped, but it´s done so well you don´t really perceive it as such. The mids aren´t sunk in a hole like sometimes with the SM64. SM64 has more bass quantity, but with less quality (it´s a tad loose). Actually the SM64 is a nice bass head IEM, it has an intentionally splashy sound that some will love and others hate. I liked it, but it isn´t exactly neutral. The highs on the SM64 are more rolled off and the soundstage is presented differently. SM64 sounds more like sound is coming from every direction while the FA4 has more forward staging. Detail retrieval is definitely higher on the FA4, I found the SM64 very forgiving of poor recordings. Build quality is no contest, FA4 wins easy. Soundstage is a bit larger on the SM64, but also less precise and directional. The SM64 is an IEM that pushes its own signature sound into all music, FA4 has more genre bandwidth and is technically superior. They are very differently tuned in the end, but the FA4 is simply a more balanced product with more mass market appeal. Some might prefer the SM64 bass, but for me the FA4 strikes a good balance there. SM64´s bass was sometimes too much and more importantly not as controlled as I would like. It really depends on the song though. Mids and highs is where I would give the nod the the FA4, but if you are looking for a more organic (at the expense of detail plus that flavour is pushed into the music regardless of the source material) coloured sound you might prefer the SM64.