Most phones have very good audio output quality via their analog headphone jack <note to self: resist urge to crack iPhone 7 joke…> if you can find earbuds that sound good. Yet that’s a big if. Most earbuds sound like crap. Of the few that sound good, some have impedance or efficiency that don’t match well to a phone. Also, while phone audio output is often very good, that does not mean excellent or reference quality, so don’t go overboard and waste money on really expensive IEMs.

I listen to mostly natural acoustic music and I’m picky about sound. The best really good IEM I’ve found is the Vsonic GR07. They cost about $100 and sound really good. To my ears, they’re comparable to a pair of full-size HD-600. They have flat, neutral response that is neither warm nor bright, but just right. The treble is smooth with good detail. Due to a phone’s audio output limitations, even with uncompressed FLAC files the extreme high frequencies are rolled off and there’s less “air”, slightly less crisp transient response.  It sounds very good, even great, but not excellent or reference quality. The GR07 is about the best quality it’s worth paying for given the limitations of the source.

The best cheap IEM I’ve found is the Vsonic VSD1S. They cost about $35, have the same high quality construction and 90% as good sound as the GR07. Comparatively, the VSD1S has a slight midrange recess, not quite as smooth or extended treble. Overall, they still have a nice neutral sound despite have a touch more “V” shaped response curve. They’re good enough to listen to for hours enjoyably without fatigue, better than most other good IEMs, but just not quite as refined as the GR-07.