What I meant by sound production is the way the headphones produce the sound (like timbre, bass, treble, etc.) I may have used the wrong term, sorry po.
Well that depends on what you want, but from a more objective standpoint try to get one that has the smoothest response curve. No sharp/narrow peaks or dips that deviate far from where 1khz is, and 20hz and 20khz (or at least 16khz) aren't too far from where 1khz is either. Of course, how smooth the graph should be can vary with the price point, ie, you can be more tolerant of response flaws at lower price ranges as long as it's comfortable.
In my case I use the Aurisonics ASG-1 primarily for comfort. The curve is somewhat similar to the LCD-2 (pre-Fazor), where the response is stronger below 1khz than above it, except it's not as smooth at either range. That said, the curve isn't too jagged, so a wide-band low shelf cut of -4dB (ie everything below 500hz reduced) and a wideband high shelf boost of +2dB (everything above 4khz boosted) gets a very smooth and balanced overall response.
I'd wait for reviews on the upcoming Fender DXA-1 - they bought Aurisonics which will now be their IEM arm. There's also the Aurisonics Eva but it's a little bit more expensive,but check with Egghead - if they have any they might put them up for sale since it's an older pre-Fender line. As long as the Fender lines are still available through Egghead instead of Audiophile it's not a problem (had a problem with Shure before, but of course not as bad as Sennheiser's and Olympus' distributor).
Hm, I am not that keen on in ears to be honest because it is uncomfortable. I prefer over ear headphones but I would try some in ears again for walking from one college to the next. (Anyone form UPLB here? huhu ang init na ngayon.)
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So what can you recommend for IEMs? I could look it up someday. So far, my college mate recommended some Audio Technicas and Sennheisers.
If you'll use them outside the problem with fullsize headphones is that they won't seal properly to block out all that noise. Anyways, what IEMs have you tried that you didn't like? An IEM shell like the Aurisonics Bravo and ASG line however mimic the outer shell of a custom IEM, spreading more of the weight outside the ear instead of putting all friction and weight on the eartip and the cable looped around over the earlobe. Sadly the new entry level, the DXA-1, uses a more traditional universal shell design,
but at least it uses a shell design similar to Shure and Westone, which tend to be more comfortable.
For China/Taiwan brands, start looking into the VSD3 and Havi B3 Pro. The latter is a more comfortable version of the Sennheiser IE8, but still not as comfortable as the VSD3. Still, that one might have a good shell design similar to Shure/Westone (the jagged diamond texture is more on the outside, not against your ear),
but the problem is the cable. It's too thick, too heavy, and is highly microphonic (tap it and you'll hear the impact). For the price of a new VSD3 plus gambling on a Lunashops cable, and all the hassles with the MMCX connector (or getting the new version with the non-replaceable cable), might as well wait and see how much the DXA-1 will be sold here first and maybe try them out also. The more you want to save money the more you need to not rush into buying anything.
Also, if you want a lot of comfort and can spend a bit more, look into Flipears. It's a local brand so no need to deal with Customs (the one with sharks at the post office) and international shipping if you need to have it reshelled for better fit or if you crack the shell. Note though that at your age the ear canal has a high probability of changing shape still so even if you take good care of it you might need a refit after two years. Not that bad though considering the comfort.
Look at who got their custom IEMs from Flipears