Update: It turns out some IEMs are for jamming into your ear holes and some aren't. The M9 and Z1R aren't. I couldn't get any of the tips to fit comfortably in my ears and was using the smallest ones. I just tried the "LL" extra large tips because someone mentioned they fit them and I kept thinking that my ears aren't super small and I should be wearing at least a medium. I then figured out that these are made to sit in the bowl of the ear, not inside the ear canal; and now the M9 and Z1R are much more comfortable for me and I still get a good seal for bass. I am revising my original post and putting it below after more comparison: I just briefly compared my IER-Z1R vs. IER-M9 vs. qdc Neptune: Z1R: Slightly recessed male vocals, slightly better sub-bass (audible down to 26 Hz) than the M9. Slightly wider soundstage than the M9, but everything sounds slightly distant. M9: Sounds slightly clearer than Z1R. Midrange is more forward. Sub-bass audible down to 27 Hz, but it is weaker than the Z1R. Mid-bass is louder than the Z1R's and much more prominent than sub-bass. Much lighter weight than the Z1R, though the difference isn't that noticeable once worn. Neptune: Much easier to drive than the Z1R and M9 which were about the same as each other. Sounds a little echoey. Much warmer than the M9 or Z1R. Less sibilance than both. Flatter frequency response while the M9 and Z1R are slightly V-shaped. Sub-bass is lacking but is audible down to 30 Hz. Seems to have very slight trouble playing bass and treble at the same time. Comfort: Z1R: 8/10 M9: 8/10 Neptune: 10/10 Sound Quality (for IEMs): Z1R: 10/10 M9: 10/10 Neptune: 6/10 Overall I prefer the M9 due to sounding less distant than the Z1R. The Z1R seems a little out of focus to me and needs to be inserted deeper than the tip design will allow. The nozzles on the M9 and Z1R are too wide to accommodate deep insertion type tips, which is why there are no flanged tips included with the M9 or Z1R. The Neptune is amazing value for the money though, costing 6x less than the M9 and 10x less than the Z1R while beating every other IEM I've heard under $400. I am currently selling the Z1R, but will continue to compare them, so this may change.