Earbud Testing

A few weeks ago I was interested in getting a pair of IEMs, or in ear monitors, for listening to music on the go. I have a set of over ear headphones and a basic two speaker setup on my computer, but neither are really portable (over ear headphones are a bit bulky for mobile use). I do have the VE Monks, a pair of earbuds that sound quite good for their cheap price, but they lack any isolation.


In my search, I stumbled across the DIY IEMs subreddit where I saw people making their own custom IEMs, usually with Knowles balanced armature (BA) drivers. Some make their own custom shells while other use universal shells like the SE535's shells. Me being interested in making things, and with my dad is travelling to China, I had him pick up some parts for a simple IEM from Taobao. I followed a guide on the subreddit. He should be back in a week and then I can get started on making it. I also ordered the Knowles GK-31732, a triple BA driver package with an integrated passive crossover. I was surprised at how much they cost, but others have said that they has a very nice sound signature and the fact that they are one unit makes it easy to use.

Knowles GK-31732, crossover visible.

I do want to find out what the values of the resistor and capacitor on the crossover are just for fun, but they won't be that useful because I won't know how the impedance of the drivers change with respect to frequency. There is an impedance plot listed for the whole GK unit in the datasheet but not for each individual driver (woofer, tweeter). There is impedance listed at a specific frequency though. The DC resistances listed will let me measure the crossover without removing the components. (Maybe I won't do this though out of fear of damaging the $44 drivers. $44 each!)

I also did some more research and found that compared to dynamic drivers, BA drivers are more detailed, but are good at producing frequencies only in a tighter range and are generally bad at reproducing lower frequencies. That's why multiple drivers are used, with each designed to operate at its best in a certain frequency range.

Of course, there is a lot of conflicting information as how "nice" something sounds is very subjective and different shells and tuning can create radically different sound signatures, sound stage, and more. I'll just have to find out for myself.

At the same time, I was looking around at reviews and prices of commercial IEMs and came across the 1More Triple Driver, which was on sale at Costco. It boasts two BA drivers and one dynamic driver, and for a cost of only $60 (okay, that is the most I've ever spent on an in-ear monitor and the world of cheap of earbuds it is rather pricey) it seemed like a good choice.

Fancy box.

Inside. (headphones removed)

The IEMs with silicone ear tips.

I got them in the mail today, and when I first tested them, they sounded absolutely horrible. The sound was incredibly muddy and muffled and everything was wonky. I had a very similar experience with the Xiaomi (1More) Hybrid IEMs, which I tested on both my phone and computer. This couldn't possibly be right. People were praising both left and right, and even the cheapest earbuds I've tried sounded better.

I thought it probably had something to do with the four pin 3.5 mm connector. I was plugging it into a three pin 3.5 mm socket, and some pins may be connecting incorrectly.

Three pin.

I used a four pin to audio and mic splitter to try to fix this issue.

At first it didn't work, but after a small twist, and moving the four pin connector around a bit, the audio quality jumped up. I won't go into describing if I like the sound signature or not, but now the IEMS were sounding like they should be.

Now I'm wondering why the Hybrids sounded so bad on my phone too, which has a proper four pin jack. I did have to do some twisting with these Triple Drivers in the four pin connector (I can't plug the connector all the way on my splitter otherwise I lose the left channel, but I can plug in my connector normally on my phone and get proper output.), and this may explain the bad connections.

I think there are slight misalignments with the connector so the the left and right channel contacts are connecting and causing serious distortions. No other accidental connections would explain such a different sound. Bridging a channel to ground would short it out and mute it, and connecting anything through the mic isn't possible because the ground contact separates the mic contact from the audio contacts. The in-line controls also would do nothing. The Android specification for in-line controls is here.

Maybe I just have really bad splitter with bad connectors. Doesn't explain the issues with the Hybrid on the phone though. Kind of stupid of me to not see this issue earlier. Oh well, time to retry the Hybrids.