IEM Technolgies


I’m behind the times. I’ve just noticed in some discussions elsewhere on the forum talk about “multiple BA IEMs”, notably in the cheap IEM threads.

If someone would like to provide a synopsis of current tech in IEMs, I’d be interested. I’ve certainly listened to standard multi-driver IEMs, also older STAX electrostatic IEMs. Never Planars in the IEM space, and I don’t know what else is out there and what I should listen for when trying them.

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As always @Torq is the go to man here. Having only recently bought the 64 Audio U18t’s I can comment a little. Firstly they’ve packed in 18 drivers on each side with 8 Low BA drivers and 8 Mid BA drivers. The other remaining 2 drivers are the much vaunted TIA (Tubless Inear Audio) type. One being for the Mids and the other for the Highs.

As well as this they also employ their APEX (Air Pressure Exchange) technology which is said to help alleviate air pressure build up in the ear canal this minimising listening fatigue. It does this via a plug in modules (apex module) which have vents of varying sizes, depending on which module is chosen. You are supplied with 2 apex modules the m15 and the m20. The m20 offering slightly less isolation -20db hence the m20, with the m15 offering -15db. The differing modules do change sound slightly but not significantly. The m20 offers a little more bass and brings a little more to the lower mids whilst the m15 gives slightly better imaging and highs.

These are just a couple of innovations in the iem arena that have crossed my path. All in all I would say they are very successful ones too.

As for planar iem’s the only ones I have tried are the iSine 20’s. You will of course read much about this polarising iem but it really is a kind of love hate with these. The sound I loved though it is my only experience with Planar’s so I cannot compare it to others. Extremely airy and dynamic to my ear the have great bass too. The only thing that stopped me keeping them was the comfort. They’re either going to be a good fit for you or they aren’t and it was very difficult for me to get any comfort, try as I might. It was a shame as they sounded great. Also I used the Cipher cable which made a huge difference to the sound over the standard cable.

Just a few of my own thoughts on a couple of iem’s ive come across.


The overwhelming majority of in-ear products use conventional dynamic drivers or balanced armatures (BAs). As @prfallon69 said, the iSine is the most widely known planar, but @antdroid has also mentioned others too. Planar drivers are so large they are not so much “in ear” as “on ear.” Similarly, the KOSS KDE-250 you own is an on ear dynamic product.

Until the rise of Chinese audio in the last few years, “In Ear Monitor” referred to Custom (CIEM) professional products. In my experience average people spoke of dynamic driver “ear buds” and never said IEM at all.

Please see below for a 36 minute presentation about the history of IEMs and the Ultimate Ears brand. This is complimented by the Wikipedia story on Jerry Harvey and UE’s page on balanced armatures. Jerry Harvey invented IEMs but later separated from UE and founded JH Audio. In brief, IEMs came from $$$$ hearing aid technology and the need for (Alex Van Halen) stage performers to hear their own performance over the amplification.


Thanks @generic that looks a great video. I will enjoy watching it. I have seen some other interviews with him but I don’t recall seeing this one, though I may have.

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I’ve gotten the opportunity to try out a ton of different IEMs (mostly under $1000) over the past couple years and here’s my thoughts on technologies:

  1. Dynamic Drivers – still the most coherent throughout frequency range and provides the biggest punch for bass impact (in general). It’s becoming harder to find dynamic driver only in-ears now especially as you move up in price.

  2. Balanced Amarture - Really good resolution. Can be limited due to physical constraints of the driver which is why #3 is a thing

  3. Multi-BA - Pack as much drivers as you can in a single shell and market it. More isn’t always better. When done right, you get a very good resolution, coherency, and extension, but when done wrong, and happens often, you get poor cross-overs and coherency/transition is bad.

  4. Hybrids (DD+BA) – in general, I think this is a good compromise. You get the quality/quantity bass of a DD plus the resolution of the BA for the upper mids and treble. Again, cross-over matters a lot, just like a speaker system with subs and bookshelf speakers.

  5. Planar - I have enjoyed the few that are out there but they have their own substantial flaws. Luckily, low distortion and and great ability to use EQ helps these out a lot and I really do enjoy iSine and the ME1 I own. The only true IEM is the RHA CL2, which has extremely good speed, attack, and resolution, but has a massive peak in the lower treble that will really mess with the tonality and create some extreme harsh sounds if you’re sensitive there. EQ does correct it though!


and piezo-electric drivers are starting to make their way into iems as well.


And Electrostats? Still only the STAX?


Shure has electrostat IEMs but I have not tried.