Volume Control

After a quick test with the new IEMs, I decided to glue the shells together permanently with epoxy. The final result is rather nice looking:

Ooh.

Triple BA Driver

After testing out the single driver IEMs, I tried out the triple driver unit with crossover, the GK-31732, as recommended by the DIY IEM subreddit and more specifically this post. When the author said the drivers would be a tight fit, he wasn't kidding. After trying my best, the SE535 shells barely "close." I couldn't get the back end to close up completely (the back lip of the shells wouldn't overlap, <1 mm), so for now I just taped the shells together.

Soldered the driver directly to the input.

Taped together.

Compared to the single drivers, this unit has far more bass (as I expected from the relatively massive woofer unit). At first I thought it was too bassy, but after realizing that my HTC One M8's "Boom Sound" feature added a peak to the bass and treble and disabling it, they sounded much better.

Also, it turns out that increasing output impedance of a source is bad, especially for balanced armature drivers (which I did by adding the 18 ohm resistors to the singe driver units). I'm going to need to tackle this volume/noise issue another way. There are adapters that add impedance to headphones, but I'm not sure if they are doing anything special other than adding resistance in series. I've seen some people using ifi's iEMatch, which is supposed to help reduce output impedance and reduce gain, which decreases volume and noise.

I'm just going to need better electrical isolation and an audio output with a lower noise floor and lower output impedance. I'll probably remove the 18 ohm resistors too (but this means they can only be used with devices that have lower noise floors).

Building IEMs

My dad came back from China yesterday with parts to make an IEM. He brought back putty, SE535 shells, ED-29689 (well the China OEM edition) balanced drivers, MMCX connectors, litz wire, one pair of filters, and a headphone cable.

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.

Water Droplet Photography Continued

After yesterday's successful attempts at taking photos of droplets, I improved the set up slightly and took some more photos.

Wood scaffolding.

Water Droplet Photography

Like astrophotography, high speed imaging is another intersection of technology and photography. I wanted to try out some basic high speed photography, and last night I took photos of water drops falling into a bowl of water.

Reflow!

Finally got around to an attempt at reflowing some SMD components. I had some PCBs I got made at OSHPark and the half the parts to populate it about two months ago, and the last half of parts a couple of weeks ago (the part I needed was back in stock). It's supposed to be a header-less version of the Particle Battery Shield from Sparkfun.

I used some bismuth solder paste (featured on this CNLohr video) since it had a low reflow temperature of around 138 °C (~280 °F). I applied it using a toothpick, then placed all the components. The fuel gauge IC was in a rather unfriendly TDFN-8 package, and I was a little unsure of using in my first solder paste job. Oh well.

Applying paste and parts.

Skillet deals.

I put the PCB on the electric skillet, bought new from Sears for about $10 on Black Friday, and dialed in the temperature to 300 °F. After about a minute, I saw shiny joints being formed, and soon enough all the parts were secured. I turned off the skillet and let everything cool.

It wasn't as difficult as I thought it was going to be:

Done! :D

I could have definitely used a bit more solder paste on some parts, but the whole thing came out really well, even the TDFN-8! Probably could have left the board on the heat for a bit longer too.

It also works!

Well, the circuit mostly works. The battery charges, but the charging indicator LED flickers uncontrollably when done charging instead of turning off. If I push on the board in some places, the blinking stops. I think there might be a bad joint somewhere, but this is pretty good. I haven't tested if I can communicate with the battery gauge yet.

Time to use more SMD components in projects to further shrink PCBs, and save more money! Also time to practice more.