For what it's worth, anyone finding the er-4s to be lacking in bass should check the depth of their fit against these photos. Everyone has different ears, so you may find a different depth works for you, but the key is the seal. When I get a good seal it is extremely hard to hear someone talk to my face from a few feet away. If you hear them muffled but still don't really have a hard time hearing them (with no music playing) then they aren't sealed enough. You should have them sealed well enough that you have to almost "try" to hear them carefully to understand what they're saying.
This is the depth that works for me. When I first got them I was worried about hitting my eardrum, so I didn't get as good of a seal, but still decent. My audiologist told me they are safe to fully insert (as you can tell by my photos). Since then I've had no problems.
(click to enlarge)
FYI, these are the large grey triple flange tips (where are they?!?) :-P ...So they are pretty deep. But once you use them a week or so they become softer and more comfortable on the ear canal. I find the triple flange tips and black foam work the best. I can squish the black foam really tight and then pull up on my ear and insert them about as deep as the triple flange. I hold them until they expand and don't feel like they'll move on me. After a minute or two they are fully settled and things sound great.
I find that the triple flange seem to have the most mids, the black foam a little more treble and bass, but almost in a slightly sibilant way. The clear triple flange are the brightest, but smooth overall. All of the differences are extremely small. In fact, I believe it's possible that it might have to do with the angle of the tips or I'm just imagining the differences. I sometimes feel like the foam aren't sibilant at all and other times just a bit. Keep in mind when I say sibilant, they aren't actually sibilant really, but just that the treble seems like it leans towards those frequencies more.
The differences are so small when I get them all tightly sealed that most people probably wouldn't even notice a difference if there even is one. It could be coincidence with the seal at the time or the angle at the time. Not sure. But in every case when they are really deep and sealed to the point where they block all noise greatly, then and only then is the bass very good. You hear further into the sub bass region and the bass is more in line with the other frequencies in terms of volume.
I recommend trying all the tips for a few days each. Let them break in. Don't be afraid to go deep. Pull up on your ear with the opposite arm, point the tip slightly upwards and twist the tip as you're inserting it (don't twist the foam tips). Sometimes I need to wiggle the tip a bit or move it in and out ever so slightly so the seal forms tightly. The phones also don't look that bad. Some people have them jutting out of their ears like they're street signs or something. I say that's not deep enough. When I get the properly seated the colored plastic part lies right outside of my ear close to the skin.
Anyhow, just a few tips for anyone having issues or trying to get more bass. If all else fails, add +3db or so of bass or EQ them a tad around 100hz and lower with a peak around 80hz. I find I don't need it personally though. I've been listening with my C5 and no adjustments and they're amazing. I'll let you know how my customs fit once I get them as well. :-)
WARNING!: You can (I have) get the tips stuck in your ear. I don't believe they pose a great risk, as they can't really easily fall deeper in the ear without being forced. I removed mine with the pliers of a leatherman. :-P Myself, by feel. Just be careful and don't poke your ear.
The best way to prevent this (I didn't do this before) is to grab the earphone body and also place your pointer finger as deep into the ear canal as you can so you are applying pressure to where the tip is around the tip sleeve (plastic nozzle). This way you can pull your ear up with the other arm, apply pressure when possible to keep the tip from coming off the nozzle and rotate the phones carefully out of your ears. It may not be necessary, but I can fairly easily grab the tip with my pointer finger to prevent it coming off.
Also, while the depth is safe, the ear canal get pretty sensitive after the first bend and more so further in. If you feel like the tips are poking and hurting a lot try tilting them different angles to get them in the center of the canal. Also, try the larger tips if you're using the smaller tips. I find I can jam the large tips in further without discomfort than the small tips. Ultimately, just be careful and slow with everything you do, but don't be afraid to put them in fairly deep like my photos.
Edited by luisdent - 3/28/13 at 4:08pm