This is isn't strictly edrum-related, but I thought it might be of interest as it's a piece of gear many of us use with our kits and elsewhere.
I found an incredible thread where they describe in detail how to make your own custom IEMs; shells, driver combinations, crossovers, the works: http://www.head-fi.org/t/430688/home-made-iems. As it was my first go at it, I decided to keep it simple by buying a universal shell that's a Shure replica, and a driver combination that's used in commercially available IEMs (the Westone UM Pro 30 among others), and comes with its own crossover circuit. All you need to know is how to use a soldering iron; other than that it's really quite simple.
This is the driver, the GK-31732, a triple driver with its ready-made crossover circuit:
First, I fitted a small (about 3 mm) length of tubing to each nozzle on the drivers to clear the way for the sound through a small piece of poron foam used to seal the drivers against the shell sound chamber/tube:
The tubing came as a gift with the drivers so it came in pretty handy. It slips tightly over the nozzles and doesn't require adhesive. I punched a couple of tiny holes in the foam with a multimeter lead, threaded the tubing through, attached it to the nozzles and then trimmed it flush with the foam.
Next, I soldered a couple of wires (scavenged from a broken pair of cheap earphones) from the little solder pads on the crossover circuit to female mmcx connectors. Positive to centre pin and negative to outer pin:
Then, I squeezed everything into place. It's pretty tight and no glue or adhesives were required:
In order to adapt the sound signature to your taste, there are these little sound dampers that go in the earphone nozzle. They come in different colour-coded values and are used to tame the high frequencies (and let through lower frequencies), as BA drivers apparently tend to have strong highs. I looked at what others were using and bought white and green dampers, and after some testing decided to use the green ones:
Last of all, you need a cable with the appropriate connectors. They sell tons of different ones on Aliexpress.
That's it. The sound quality is fantastic (I like them much more than some Shure 215's I have), they isolate from external noise really well, and aside from having to solder a few wires, it's a very easy project – once I had all the parts it took about 20 minutes to put it all together. That said, keep in mind that the fact you built something yourself automatically raises the perceived quality by about 25%
Shell (€11/pair): http://es.aliexpress.com/store/product/High-quality-C0-Repair-DIY-Unit-Housing-Shell-SE535-se425-se315-se215-W40-Earphone/333670_32499329423.html?spm=2114.30011108.3.27.LkI lSt&ws_ab_test=searchweb201556_0,searchweb201602_4 _10037_10017_10044_10043_507_10032_10042,searchweb 201603_2&btsid=832b0778-a57f-430c-86cf-2249bc0bfa32
Drivers (€75/pair): http://es.aliexpress.com/item/Free-Shipping-2pcs-pair-DIY-Earphones-GK-31732-Experience-Balance-Armature-Speaker-Receiver-Earphone-Accessories-from/1000001308317.html?spm=2114.13010608.0.81.kNzP49
MMCX connectors (€0.54 each): http://es.aliexpress.com/item/NEW-MM...08.0.89.kNzP49 These aren't actually the right ones; you need ones with a notch in the body so it fits on a ridge in the shell and stays put. I used a hacksaw to make the notch.
Dampers (€1.52 each): http://es.aliexpress.com/item/Unidad...08.0.57.kNzP49
Cable (€7): http://es.aliexpress.com/item/Earpho...08.0.65.kNzP49
These prices fluctuate and may not be the same if you check them now. If you see they're more expensive, check in regularly and you'll probably find they go down again.
The total cost comes to around €100. Not exactly cheap and you need to be careful when soldering and handling the drivers because they're tiny. They come in pairs so even if you mess just one up you automatically blow €75. However, a set of Westone UMPro 30's will set you back about €400, so the difference is not to be sneezed at, and I honestly doubt there's a €300 difference in sound quality between those and mine – they're probably actually quite close. Plus, the satisfaction of having put them together myself and being able to repair them if need be is rewarding in itself. Having screws on the shells instead of gluing them together is very handy if you ever have to/want to swap out or repair anything, and the absence of any adhesives also makes swapping out components a breeze.
If you're feeling adventurous (and have a lot of time on your hands), check out the head-fi thread I linked to above. It's amazing what the people there have done and the amount of information there is on making custom shells, crossovers, multiple driver setups, etc. A lot of the IEMs there are works of art. What I've done is the easiest, simplest (and laziest) build you can do, and though I'd love to, I don't have the time nor budget to get into the world of DIY custom IEMs...
Anyway, hope someone finds this of interest and feel free to ask any questions.