In Ear Monitors (i.e. headphones that go inside your ear)

Reviewing:

* Etymotic HF5 ($120)
* TRN-V80 ($45)
* KZ ZS10 ($45)
* Mee Electronics M6Pro ($50)
* Mee Electronics M6 ($15)

A dynamic driver is a miniaturized conventional speaker. It has a cone that moves air back and forth, pushed  and pulled by a tiny little electromagnetic piston. A balanced armature has a membrane instead of a cone, and the membrane is pushed and pulled by a diving board (the armature) which is being pulled in each direction by an electromagnetic coil. BAs are very efficient, very sensitive, and very hard to get right -- so hard that the market is dominated by two manufacturers, Knowles and Sonion.

High-end in-ear-monitors derive from Van Halen's audio engineer, Jerry Harvey, who took the technology that was previously mostly used for hearing aids and turned it into tiny speakers that fit inside molds of Alex Van Halen's ears. That allowed the rest of the world to be blocked out, and so a [relatively] quiet signal could be pushed right to the musician.

Etymotic, a company that originally made audiology equipment (and hearing aids) has been making high and mid-range IEMs for about 20 years. Their claim to fame is accuracy.

The HF5 is a single balanced-armature driver; the Mee M6 and M6Pro are single dynamic drivers; the TRN-V80 is two dynamic drivers and two BAs; the KZ ZS10 are a single dynamic driver plus 4 BAs.

All of these are very good IEMs, except the M6, which is mediocre. The M6 is also cheap, sweatproof, and has permanently attached cables, which means that in a year or three, they will be disposable. It's better than whatever came with your cellphone, but that's about it.

(I really don't know why Mee decided to give the M6Pro that name. They're about the same size, that's all.)

I won't talk more about the M6.

All of the rest, then, have very good sound quality in the middle range of frequencies -- from about 150Hz up to 3000Hz. The M6Pro is substantially less efficient than the others, and so will be quieter for any given amplification level. The HF5 produces notably less bass than the other devices, although it appears to be very accurate. If you want more bass, you'll need to add it yourself -- but only under 40Hz or so. The M6Pro produces a little more bass, but it doesn't emphasize it to rock concert levels. The V80 and the ZS10 produce quite a lot of bass, while remaining reasonably accurate apart from that.

If you're mixing music and you want the most neutral sound available, go with an Etymotic single BA. If you are playing music and want a cheap but good monitor, get the Mee M6Pro. And if you're just walking around and listening to music, either the TRN or KZ will be very nice, for not too much money.

In all cases, using the right eartip is essential. People are different, and you may want a different sized tip in each ear. Possibly you can't stand deep insertion (so avoid the Etymotic and 3-flanged silicone eartips. Possibly foam irritates your ear, so avoid the Comply brand and similar tips. The rubber mushroom eartips are pretty much guaranteed to be the wrong type for all of them, though - at least for me.