Inexpensive In Ear Monitors and rigged up ear mold adapters

A while back, my friend Jason was telling me about some really affordable in ear monitors that amazon was selling. These seemed to have some buzz going online, and it sounded like other audio pros he knew had them or were interested in them as well. [Some review links here: rtings, Soundphile, Forbes, Audiofool]

The product in question is the KZ AS10, a Chinese import retailing at Amazon under $60. [ and other product links here are Amazon referrals. Feel free to search for them yourself if you don’t want to mess with it] They can be found even cheaper on Alibaba and other import sites if you’re willing to gamble with authenticity and long shipping times.

Stock photo from Amazon

I was a little curious, but I had no real need for IEMs, until I tried to practice using acoustic drums outside of a band context for the first time in some years. (shoutout to soundspace in Indy – If you need a rehearsal space downtown-ish, check them out) I tried playing along to a CD with my apple ear buds, but the drums drowned everything out. I used to have some sealed vic firth headphones that were better for this, but I couldn’t find them. I think I threw them out because they were so uncomfortable. For that session, I ended up having to blast the CD through a PA system to hear it, and even that wasn’t great.. This kind of practice seemed like a decent use for some $60 IEMs. So I bought em.

I’m no stranger to the world of “Chi-fi”. A few years ago I bought some of the much ballyhoo-ed Mrice E300’s, again, from Amazon. I think I paid less than $20 for those, and while I didn’t find enough a reason to use them for much more than a backup for listing to tv on the iPad while laying in bed, they aren’t bad, and the low price keeps me from feeling too bad about the purchase. I’ve heard them referred to as “beater ear buds for audiophiles”, which seems like a good way to put it. I don’t know, maybe they are just over-hyped, but not any worse than the stuff being sold for a lot more $$, IMO. [for in depth reviews of the E300 check out these links: Wired, AudioBudget, GadgetViper, Jan Beta]

Amazon stock photo

The KZs showed up in a modest but not totally useless box with 3 sizes of ear tips, and an over-the-ear cable with mini (1/8″) jack. They are pretty comfortable. I listened to some music, and played some video games through them and found them to sound pretty ok, if not actually good. I’ve heard of people saying they have a “burn in” period, but I haven’t taken the time to do anything like that.

I guess the real selling point with these is the low end.. the KZs have 5 drivers and they are all of the balanced armature type. I don’t know much about it, but apparently balanced armatures aren’t great at low frequency production, so other similar IEMs/headphones use a different kind of driver, dynamic drivers, for the low end. The KZ AS10 seems to be the first wave of products using a new balanced armature that can do the low stuff. And these did have some low end. The weak link in it all might be the rubber ear tips though – if you get a good seal by pressing the headphones into your ear and holding them there, the low frequencies sound great, but otherwise it’s kind of hit or miss. I’ve heard people say that the memory foam ear tips that you can buy separately work better.

One thing that I really like a lot about these is that they get loud without a ton of power, which I assume has something to do with the balanced armatures. A lot of the headphones I have need an additional dedicated headphone amp to drive at realistic volumes. The KZs had no problems here. Everything I plugged them into could push them just fine.

After I had used them for a bit, I got to wondering how they would do when connected to ear molds. I think for me, this idea is one of the more interesting parts of IEMs – stage use, and blocking out other sounds so you can completely control what’s in your ears. I have some old Sensaphonics silicone ear-mold “musicians ear plugs” that I got from Dawn at earEverything 10 or so years ago, and figured there had to be a way I could connect these to the headphones.. and there was..

The Senaphonics use filters made by a company called etymolic research to block sounds. I figured I could buy some extra filters and drill them to accommodate the KZ’s. I looked around, and found that the filters are kind of expensive.. ($30/pair) and then used this all as an excuse to play with some 3D modeling and printing. I modeled the exterior of the filter matching the originals, and made a channel through it that would fit the nozzle of the KZ. There are some little retaining barbs for the rubber tips, and I tried to design a groove for them, but didn’t anticipate it working really well since it was all pushing the tolerance of most 3D printers. And speaking of 3D printers, I don’t have one, and I don’t know anyone close by who has a real hi res one, so I decided to use this as an opportunity to try out

Shapeways worked out pretty well.. I did 2 of the filter “blanks” each in two types of material, just to see what it would be like. The total came to $30, which for such little things, seemed like a lot of money, but hey, it’s an experiment. They somehow only delivered 3 of the 4 pieces, which was kind of annoying, but thankfully, I got both of the ones in the material that I liked better.

Shapeways print on the left, etymolic research filter on the right

The blanks fit in my ear molds fine, but the channel for the KZs was a little narrow. I busted out the Italian file set and opened them up pretty quickly. The fit is snug. I had imagined that the fit wouldn’t be that tight and I’d need to put some rubber cement on to seal them, but it seems to be unnecessary. Re: the retention barbs – the barbs didn’t seem to cause a problem, though I suspect the ductility of the headphone tube is the cause of this, and may fatigue if I take these on and off frequently.

When connected to the ear molds, the whole thing sticks out from my head quite a bit, but the ear-loop cable still goes over my ear and at least so far hasn’t been uncomfortable. The overall seal of the headphones is definitely better and the low end more prominent. I do have some concern over the ear-molds and adapter altering the sound passing through them. the adapter’s channel has a reduction in it. I guess the place to start on figuring this out might be Kirchhoff, but it’s all stuff beyond me, and I really don’t have the interest.

ear-mold on KZ AS10 earphone using adapter
the headphones stick out a little further from my ear when used with the ear-molds and adapters

I’m toying with the idea of making a pile of these and selling them, but I’m not sure. If you’re interested, drop me a line.

Sound comparisons from my experiment:

I used the first couple tracks off of Hum’s Downward Is Heavenward as a reference, played lossily from Spotify through an Avid MBox mini 3. I listened with Sennheiser HD600’s and Mackie HR824 nearfield monitors for comparisons. Take all these opinions with a grain of salt, because I certainly am no Golden Ear.

Listening to the KZs with the earmolds and adapters, the bass was definitely more present than with the rubber tips, or in my monitors. Bordering on Metallica – ..And Justice For All level “whoomping”. It didn’t necessarily sound unrealistic or over accentuated the way Beats headphones sound, but I think these just go lower than any of my other references. Overall, the music didn’t seem to have the “glue” that it does when listening on other devices. Maybe more mids than usual, but I don’t know if that’s true or me second guessing myself.

I switched to the HD600’s. Whoa.. these really make the high end come forward in a crispy way, though I don’t think I necessarily like it. A little more of the glue that was missing with the KZs/ear molds. Nothing going on in the low end, which isn’t surprising since these are open backed.

I switched to the KZs with the rubber tips installed. The low bass is gone. There are still lows and more than the HD600s had. Glue is still missing. Highs are less prominent/affected than the HD600s. I had the same questioning of the mids.

Finally, I brought up the Mackies.. Probably the reference I’m most used to, and it shows. None of the low low stuff. The glue is here. The highs seem “normal” and not accentuated in any way.

These comparisons all may be for naught because honestly, IEMs aren’t for critical monitoring, they’re for the stage. Well, I guess they’re for whatever you want them to be for. It would be nice to compare them to one of the more traditional IEM options like the Shures or Westones, but I don’t have any handy. At the very least, the KZs are an interesting toy for $60 and maybe the option of a rigged up ear mold configuration adds to the novelty.